Move a bunch of trans into trans_common, including the context structures.

Probably more should be moved or split off into other files. My algorithm
was something along the lines of: move the contexts and their transitive
dependencies along with some functions to work with them. I stopped when
I was going to have to start pulling glue generation, which really
should go into a trans_glue file.

7 files changed, 369 insertions, 388 deletions

diff --git a/src/comp/back/link.rs b/src/comp/back/link.rs
index ab9f47e3cc0..2b61ca6078e 100644
--- a/src/comp/back/link.rs
+++ b/src/comp/back/link.rs
@@ -2,9 +2,9 @@
 import driver::session;
 import lib::llvm::llvm;
 import front::attr;
-import middle::trans;
 import middle::ty;
 import metadata::encoder;
+import middle::trans_common::crate_ctxt;
 import std::str;
 import std::fs;
 import std::ivec;
@@ -13,7 +13,6 @@ import option::some;
 import option::none;
 import std::sha1::sha1;
 import std::sort;
-import trans::crate_ctxt;
 import syntax::ast;
 import syntax::print::pprust;
 import lib::llvm::llvm::ModuleRef;
diff --git a/src/comp/metadata/encoder.rs b/src/comp/metadata/encoder.rs
index e0c9d544742..2896fa57ddf 100644
--- a/src/comp/metadata/encoder.rs
+++ b/src/comp/metadata/encoder.rs
@@ -11,7 +11,7 @@ import std::ebmlivec;
 import std::map;
 import syntax::ast::*;
 import common::*;
-import middle::trans::crate_ctxt;
+import middle::trans_common::crate_ctxt;
 import middle::ty;
 import middle::ty::node_id_to_monotype;
 import front::attr;
diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index 06734b0b362..c6b90092881 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -75,341 +75,6 @@ import trans_comm::trans_spawn;
 import trans_comm::trans_send;
 import trans_comm::trans_recv;
 
-obj namegen(mutable int i) {
-    fn next(str prefix) -> str { i += 1; ret prefix + int::str(i); }
-}
-
-type derived_tydesc_info = rec(ValueRef lltydesc, bool escapes);
-
-type glue_fns = rec(ValueRef no_op_type_glue);
-
-type tydesc_info =
-    rec(ty::t ty,
-        ValueRef tydesc,
-        ValueRef size,
-        ValueRef align,
-        mutable option::t[ValueRef] copy_glue,
-        mutable option::t[ValueRef] drop_glue,
-        mutable option::t[ValueRef] free_glue,
-        mutable option::t[ValueRef] cmp_glue,
-        uint[] ty_params);
-
-
-/*
- * A note on nomenclature of linking: "upcall", "extern" and "native".
- *
- * An "extern" is an LLVM symbol we wind up emitting an undefined external
- * reference to. This means "we don't have the thing in this compilation unit,
- * please make sure you link it in at runtime". This could be a reference to
- * C code found in a C library, or rust code found in a rust crate.
- *
- * A "native" is an extern that references C code. Called with cdecl.
- *
- * An upcall is a native call generated by the compiler (not corresponding to
- * any user-written call in the code) into librustrt, to perform some helper
- * task such as bringing a task to life, allocating memory, etc.
- *
- */
-type stats =
-    rec(mutable uint n_static_tydescs,
-        mutable uint n_derived_tydescs,
-        mutable uint n_glues_created,
-        mutable uint n_null_glues,
-        mutable uint n_real_glues,
-        @mutable (tup(str,int)[]) fn_times);
-
-
-// Crate context.  Every crate we compile has one of these.
-type crate_ctxt =
-    rec(session::session sess,
-        ModuleRef llmod,
-        target_data td,
-        type_names tn,
-        hashmap[str, ValueRef] externs,
-        hashmap[str, ValueRef] intrinsics,
-
-        // A mapping from the def_id of each item in this crate to the address
-        // of the first instruction of the item's definition in the executable
-        // we're generating.
-        hashmap[ast::node_id, ValueRef] item_ids,
-        ast_map::map ast_map,
-        hashmap[ast::node_id, str] item_symbols,
-        mutable option::t[ValueRef] main_fn,
-        link::link_meta link_meta,
-
-        // TODO: hashmap[tup(tag_id,subtys), @tag_info]
-        hashmap[ty::t, uint] tag_sizes,
-        hashmap[ast::node_id, ValueRef] discrims,
-        hashmap[ast::node_id, str] discrim_symbols,
-        hashmap[ast::node_id, ValueRef] fn_pairs,
-        hashmap[ast::node_id, ValueRef] consts,
-        hashmap[ast::node_id, ()] obj_methods,
-        hashmap[ty::t, @tydesc_info] tydescs,
-        hashmap[str, ValueRef] module_data,
-        hashmap[ty::t, TypeRef] lltypes,
-        @glue_fns glues,
-        namegen names,
-        std::sha1::sha1 sha,
-        hashmap[ty::t, str] type_sha1s,
-        hashmap[ty::t, str] type_short_names,
-        ty::ctxt tcx,
-        stats stats,
-        @upcall::upcalls upcalls,
-        TypeRef rust_object_type,
-        TypeRef tydesc_type,
-        TypeRef task_type);
-
-type local_ctxt =
-    rec(str[] path,
-        str[] module_path,
-        ast::ty_param[] obj_typarams,
-        ast::obj_field[] obj_fields,
-        @crate_ctxt ccx);
-
-
-// Types used for llself.
-type val_self_pair = rec(ValueRef v, ty::t t);
-
-
-// Function context.  Every LLVM function we create will have one of these.
-type fn_ctxt =
-    rec(
-        // The ValueRef returned from a call to llvm::LLVMAddFunction; the
-        // address of the first instruction in the sequence of instructions
-        // for this function that will go in the .text section of the
-        // executable we're generating.
-        ValueRef llfn,
-
-        // The three implicit arguments that arrive in the function we're
-        // creating.  For instance, foo(int, int) is really foo(ret*, task*,
-        // env*, int, int).  These are also available via
-        // llvm::LLVMGetParam(llfn, uint) where uint = 1, 2, 0 respectively,
-        // but we unpack them into these fields for convenience.
-
-        // Points to the current task.
-        ValueRef lltaskptr,
-
-        // Points to the current environment (bindings of variables to
-        // values), if this is a regular function; points to the current
-        // object, if this is a method.
-        ValueRef llenv,
-
-        // Points to where the return value of this function should end up.
-        ValueRef llretptr,
-
-        // The next three elements: "hoisted basic blocks" containing
-        // administrative activities that have to happen in only one place in
-        // the function, due to LLVM's quirks.
-
-        // A block for all the function's static allocas, so that LLVM will
-        // coalesce them into a single alloca call.
-        mutable BasicBlockRef llstaticallocas,
-
-        // A block containing code that copies incoming arguments to space
-        // already allocated by code in one of the llallocas blocks.  (LLVM
-        // requires that arguments be copied to local allocas before allowing
-        // most any operation to be performed on them.)
-        mutable BasicBlockRef llcopyargs,
-
-        // The first block containing derived tydescs received from the
-        // runtime.  See description of derived_tydescs, below.
-        mutable BasicBlockRef llderivedtydescs_first,
-
-        // The last block of the llderivedtydescs group.
-        mutable BasicBlockRef llderivedtydescs,
-
-        // A block for all of the dynamically sized allocas.  This must be
-        // after llderivedtydescs, because these sometimes depend on
-        // information computed from derived tydescs.
-        mutable BasicBlockRef lldynamicallocas,
-
-        // FIXME: Is llcopyargs actually the block containing the allocas for
-        // incoming function arguments?  Or is it merely the block containing
-        // code that copies incoming args to space already alloca'd by code in
-        // llallocas?
-
-        // The 'self' object currently in use in this function, if there is
-        // one.
-        mutable option::t[val_self_pair] llself,
-
-        // If this function is actually a iter, a block containing the code
-        // called whenever the iter calls 'put'.
-        mutable option::t[ValueRef] lliterbody,
-
-        // The next four items: hash tables mapping from AST def_ids to
-        // LLVM-stuff-in-the-frame.
-
-        // Maps arguments to allocas created for them in llallocas.
-        hashmap[ast::node_id, ValueRef] llargs,
-
-        // Maps fields in objects to pointers into the interior of llself's
-        // body.
-        hashmap[ast::node_id, ValueRef] llobjfields,
-
-        // Maps the def_ids for local variables to the allocas created for
-        // them in llallocas.
-        hashmap[ast::node_id, ValueRef] lllocals,
-
-        // The same as above, but for variables accessed via the frame pointer
-        // we pass into an iter, for access to the static environment of the
-        // iter-calling frame.
-        hashmap[ast::node_id, ValueRef] llupvars,
-
-        // For convenience, a vector of the incoming tydescs for each of this
-        // functions type parameters, fetched via llvm::LLVMGetParam.  For
-        // example, for a function foo[A, B, C](), lltydescs contains the
-        // ValueRefs for the tydescs for A, B, and C.
-        mutable ValueRef[] lltydescs,
-
-        // Derived tydescs are tydescs created at runtime, for types that
-        // involve type parameters inside type constructors.  For example,
-        // suppose a function parameterized by T creates a vector of type
-        // [T].  The function doesn't know what T is until runtime, and the
-        // function's caller knows T but doesn't know that a vector is
-        // involved.  So a tydesc for [T] can't be created until runtime,
-        // when information about both "[T]" and "T" are available.  When such
-        // a tydesc is created, we cache it in the derived_tydescs table for
-        // the next time that such a tydesc is needed.
-        hashmap[ty::t, derived_tydesc_info] derived_tydescs,
-
-        // The source span where this function comes from, for error
-        // reporting.
-        span sp,
-
-        // This function's enclosing local context.
-        @local_ctxt lcx);
-
-tag cleanup {
-    clean(fn(&@block_ctxt) -> result);
-    clean_temp(ValueRef, fn(&@block_ctxt) -> result);
-}
-
-fn add_clean(&@block_ctxt cx, ValueRef val, ty::t ty) {
-    find_scope_cx(cx).cleanups += ~[clean(bind drop_slot(_, val, ty))];
-}
-fn add_clean_temp(&@block_ctxt cx, ValueRef val, ty::t ty) {
-    find_scope_cx(cx).cleanups += ~[clean_temp(val,
-                                               bind drop_ty(_, val, ty))];
-}
-
-// Note that this only works for temporaries. We should, at some point, move
-// to a system where we can also cancel the cleanup on local variables, but
-// this will be more involved. For now, we simply zero out the local, and the
-// drop glue checks whether it is zero.
-fn revoke_clean(&@block_ctxt cx, ValueRef val) {
-    auto sc_cx = find_scope_cx(cx);
-    auto found = -1;
-    auto i = 0;
-    for (cleanup c in sc_cx.cleanups) {
-        alt (c) {
-            case (clean_temp(?v, _)) {
-                if (v as uint == val as uint) { found = i; break; }
-            }
-            case (_) {}
-        }
-        i += 1;
-    }
-    // The value does not have a cleanup associated with it. Might be a
-    // constant or some immediate value.
-    if (found == -1) { ret; }
-    // We found the cleanup and remove it
-    sc_cx.cleanups = std::ivec::slice(sc_cx.cleanups, 0u, found as uint) +
-        std::ivec::slice(sc_cx.cleanups, found as uint + 1u,
-                         std::ivec::len(sc_cx.cleanups));
-}
-
-tag block_kind {
-
-    // A scope block is a basic block created by translating a block { ... }
-    // the the source language.  Since these blocks create variable scope, any
-    // variables created in them that are still live at the end of the block
-    // must be dropped and cleaned up when the block ends.
-    SCOPE_BLOCK;
-
-    // A basic block created from the body of a loop.  Contains pointers to
-    // which block to jump to in the case of "continue" or "break", with the
-    // "continue" block optional, because "while" and "do while" don't support
-    // "continue" (TODO: is this intentional?)
-    LOOP_SCOPE_BLOCK(option::t[@block_ctxt], @block_ctxt);
-
-    // A non-scope block is a basic block created as a translation artifact
-    // from translating code that expresses conditional logic rather than by
-    // explicit { ... } block structure in the source language.  It's called a
-    // non-scope block because it doesn't introduce a new variable scope.
-    NON_SCOPE_BLOCK;
-}
-
-
-// Basic block context.  We create a block context for each basic block
-// (single-entry, single-exit sequence of instructions) we generate from Rust
-// code.  Each basic block we generate is attached to a function, typically
-// with many basic blocks per function.  All the basic blocks attached to a
-// function are organized as a directed graph.
-type block_ctxt =
-    rec(
-        // The BasicBlockRef returned from a call to
-        // llvm::LLVMAppendBasicBlock(llfn, name), which adds a basic block to
-        // the function pointed to by llfn.  We insert instructions into that
-        // block by way of this block context.
-        BasicBlockRef llbb,
-
-        // The llvm::builder object serving as an interface to LLVM's
-        // LLVMBuild* functions.
-        builder build,
-
-        // The block pointing to this one in the function's digraph.
-        block_parent parent,
-
-        // The 'kind' of basic block this is.
-        block_kind kind,
-
-        // A list of functions that run at the end of translating this block,
-        // cleaning up any variables that were introduced in the block and
-        // need to go out of scope at the end of it.
-        mutable cleanup[] cleanups,
-
-        // The source span where this block comes from, for error reporting.
-        span sp,
-
-        // The function context for the function to which this block is
-        // attached.
-        @fn_ctxt fcx);
-
-
-// FIXME: we should be able to use option::t[@block_parent] here but
-// the infinite-tag check in rustboot gets upset.
-tag block_parent { parent_none; parent_some(@block_ctxt); }
-
-type result = rec(@block_ctxt bcx, ValueRef val);
-type result_t = rec(@block_ctxt bcx, ValueRef val, ty::t ty);
-
-fn extend_path(@local_ctxt cx, &str name) -> @local_ctxt {
-    ret @rec(path=cx.path + ~[name] with *cx);
-}
-
-fn rslt(@block_ctxt bcx, ValueRef val) -> result {
-    ret rec(bcx=bcx, val=val);
-}
-
-fn ty_str(type_names tn, TypeRef t) -> str {
-    ret lib::llvm::type_to_str(tn, t);
-}
-
-fn val_ty(ValueRef v) -> TypeRef { ret llvm::LLVMTypeOf(v); }
-
-fn val_str(type_names tn, ValueRef v) -> str { ret ty_str(tn, val_ty(v)); }
-
-
-// Returns the nth element of the given LLVM structure type.
-fn struct_elt(TypeRef llstructty, uint n) -> TypeRef {
-    auto elt_count = llvm::LLVMCountStructElementTypes(llstructty);
-    assert (n < elt_count);
-    auto elt_tys = std::ivec::init_elt(T_nil(), elt_count);
-    llvm::LLVMGetStructElementTypes(llstructty, std::ivec::to_ptr(elt_tys));
-    ret llvm::LLVMGetElementType(elt_tys.(n));
-}
-
-
 // This function now fails if called on a type with dynamic size (as its
 // return value was always meaningless in that case anyhow). Beware!
 //
@@ -783,17 +448,6 @@ fn trans_shared_free(&@block_ctxt cx, ValueRef v) -> result {
     ret rslt(cx, C_int(0));
 }
 
-fn find_scope_cx(&@block_ctxt cx) -> @block_ctxt {
-    if (cx.kind != NON_SCOPE_BLOCK) { ret cx; }
-    alt (cx.parent) {
-        case (parent_some(?b)) { ret find_scope_cx(b); }
-        case (parent_none) {
-            cx.fcx.lcx.ccx.sess.bug("trans::find_scope_cx() " +
-                                        "called on parentless block_ctxt");
-        }
-    }
-}
-
 fn umax(&@block_ctxt cx, ValueRef a, ValueRef b) -> ValueRef {
     auto cond = cx.build.ICmp(lib::llvm::LLVMIntULT, a, b);
     ret cx.build.Select(cond, b, a);
@@ -8518,12 +8172,12 @@ fn create_crate_map(&@crate_ctxt ccx) -> ValueRef {
     ret map;
 }
 
-fn write_metadata(&@trans::crate_ctxt cx, &@ast::crate crate) {
+fn write_metadata(&@crate_ctxt cx, &@ast::crate crate) {
     if (!cx.sess.get_opts().library) { ret; }
     auto llmeta = C_postr(metadata::encoder::encode_metadata(cx, crate));
     auto llconst = trans_common::C_struct(~[llmeta]);
     auto llglobal =
-        llvm::LLVMAddGlobal(cx.llmod, trans::val_ty(llconst),
+        llvm::LLVMAddGlobal(cx.llmod, val_ty(llconst),
                             str::buf("rust_metadata"));
     llvm::LLVMSetInitializer(llglobal, llconst);
     llvm::LLVMSetSection(llglobal, str::buf(x86::get_meta_sect_name()));
diff --git a/src/comp/middle/trans_alt.rs b/src/comp/middle/trans_alt.rs
index 6ca0caeeef1..fa53c868536 100644
--- a/src/comp/middle/trans_alt.rs
+++ b/src/comp/middle/trans_alt.rs
@@ -9,14 +9,9 @@ import lib::llvm::llvm;
 import lib::llvm::llvm::ValueRef;
 import lib::llvm::llvm::TypeRef;
 import lib::llvm::llvm::BasicBlockRef;
-import trans::result;
-import trans::rslt;
-import trans::crate_ctxt;
-import trans::block_ctxt;
 import trans::new_sub_block_ctxt;
 import trans::new_scope_block_ctxt;
 import trans::load_if_immediate;
-import trans::val_ty;
 import ty::pat_ty;
 import syntax::ast;
 import syntax::ast::def_id;
diff --git a/src/comp/middle/trans_common.rs b/src/comp/middle/trans_common.rs
index 65c1bfb956e..9f2014b2a2d 100644
--- a/src/comp/middle/trans_common.rs
+++ b/src/comp/middle/trans_common.rs
@@ -57,9 +57,358 @@ import syntax::print::pprust::expr_to_str;
 import syntax::print::pprust::path_to_str;
 
 // FIXME: These should probably be pulled in here too.
-import trans::crate_ctxt;
 import trans::type_of_fn_full;
-import trans::val_ty;
+import trans::drop_slot;
+import trans::drop_ty;
+
+obj namegen(mutable int i) {
+    fn next(str prefix) -> str { i += 1; ret prefix + int::str(i); }
+}
+
+type derived_tydesc_info = rec(ValueRef lltydesc, bool escapes);
+
+type glue_fns = rec(ValueRef no_op_type_glue);
+
+type tydesc_info =
+    rec(ty::t ty,
+        ValueRef tydesc,
+        ValueRef size,
+        ValueRef align,
+        mutable option::t[ValueRef] copy_glue,
+        mutable option::t[ValueRef] drop_glue,
+        mutable option::t[ValueRef] free_glue,
+        mutable option::t[ValueRef] cmp_glue,
+        uint[] ty_params);
+
+/*
+ * A note on nomenclature of linking: "upcall", "extern" and "native".
+ *
+ * An "extern" is an LLVM symbol we wind up emitting an undefined external
+ * reference to. This means "we don't have the thing in this compilation unit,
+ * please make sure you link it in at runtime". This could be a reference to
+ * C code found in a C library, or rust code found in a rust crate.
+ *
+ * A "native" is an extern that references C code. Called with cdecl.
+ *
+ * An upcall is a native call generated by the compiler (not corresponding to
+ * any user-written call in the code) into librustrt, to perform some helper
+ * task such as bringing a task to life, allocating memory, etc.
+ *
+ */
+type stats =
+    rec(mutable uint n_static_tydescs,
+        mutable uint n_derived_tydescs,
+        mutable uint n_glues_created,
+        mutable uint n_null_glues,
+        mutable uint n_real_glues,
+        @mutable (tup(str,int)[]) fn_times);
+
+// Crate context.  Every crate we compile has one of these.
+type crate_ctxt =
+    rec(session::session sess,
+        ModuleRef llmod,
+        target_data td,
+        type_names tn,
+        hashmap[str, ValueRef] externs,
+        hashmap[str, ValueRef] intrinsics,
+
+        // A mapping from the def_id of each item in this crate to the address
+        // of the first instruction of the item's definition in the executable
+        // we're generating.
+        hashmap[ast::node_id, ValueRef] item_ids,
+        ast_map::map ast_map,
+        hashmap[ast::node_id, str] item_symbols,
+        mutable option::t[ValueRef] main_fn,
+        link::link_meta link_meta,
+
+        // TODO: hashmap[tup(tag_id,subtys), @tag_info]
+        hashmap[ty::t, uint] tag_sizes,
+        hashmap[ast::node_id, ValueRef] discrims,
+        hashmap[ast::node_id, str] discrim_symbols,
+        hashmap[ast::node_id, ValueRef] fn_pairs,
+        hashmap[ast::node_id, ValueRef] consts,
+        hashmap[ast::node_id, ()] obj_methods,
+        hashmap[ty::t, @tydesc_info] tydescs,
+        hashmap[str, ValueRef] module_data,
+        hashmap[ty::t, TypeRef] lltypes,
+        @glue_fns glues,
+        namegen names,
+        std::sha1::sha1 sha,
+        hashmap[ty::t, str] type_sha1s,
+        hashmap[ty::t, str] type_short_names,
+        ty::ctxt tcx,
+        stats stats,
+        @upcall::upcalls upcalls,
+        TypeRef rust_object_type,
+        TypeRef tydesc_type,
+        TypeRef task_type);
+
+type local_ctxt =
+    rec(str[] path,
+        str[] module_path,
+        ast::ty_param[] obj_typarams,
+        ast::obj_field[] obj_fields,
+        @crate_ctxt ccx);
+
+// Types used for llself.
+type val_self_pair = rec(ValueRef v, ty::t t);
+
+// Function context.  Every LLVM function we create will have one of these.
+type fn_ctxt =
+    rec(
+        // The ValueRef returned from a call to llvm::LLVMAddFunction; the
+        // address of the first instruction in the sequence of instructions
+        // for this function that will go in the .text section of the
+        // executable we're generating.
+        ValueRef llfn,
+
+        // The three implicit arguments that arrive in the function we're
+        // creating.  For instance, foo(int, int) is really foo(ret*, task*,
+        // env*, int, int).  These are also available via
+        // llvm::LLVMGetParam(llfn, uint) where uint = 1, 2, 0 respectively,
+        // but we unpack them into these fields for convenience.
+
+        // Points to the current task.
+        ValueRef lltaskptr,
+
+        // Points to the current environment (bindings of variables to
+        // values), if this is a regular function; points to the current
+        // object, if this is a method.
+        ValueRef llenv,
+
+        // Points to where the return value of this function should end up.
+        ValueRef llretptr,
+
+        // The next three elements: "hoisted basic blocks" containing
+        // administrative activities that have to happen in only one place in
+        // the function, due to LLVM's quirks.
+
+        // A block for all the function's static allocas, so that LLVM will
+        // coalesce them into a single alloca call.
+        mutable BasicBlockRef llstaticallocas,
+
+        // A block containing code that copies incoming arguments to space
+        // already allocated by code in one of the llallocas blocks.  (LLVM
+        // requires that arguments be copied to local allocas before allowing
+        // most any operation to be performed on them.)
+        mutable BasicBlockRef llcopyargs,
+
+        // The first block containing derived tydescs received from the
+        // runtime.  See description of derived_tydescs, below.
+        mutable BasicBlockRef llderivedtydescs_first,
+
+        // The last block of the llderivedtydescs group.
+        mutable BasicBlockRef llderivedtydescs,
+
+        // A block for all of the dynamically sized allocas.  This must be
+        // after llderivedtydescs, because these sometimes depend on
+        // information computed from derived tydescs.
+        mutable BasicBlockRef lldynamicallocas,
+
+        // FIXME: Is llcopyargs actually the block containing the allocas for
+        // incoming function arguments?  Or is it merely the block containing
+        // code that copies incoming args to space already alloca'd by code in
+        // llallocas?
+
+        // The 'self' object currently in use in this function, if there is
+        // one.
+        mutable option::t[val_self_pair] llself,
+
+        // If this function is actually a iter, a block containing the code
+        // called whenever the iter calls 'put'.
+        mutable option::t[ValueRef] lliterbody,
+
+        // The next four items: hash tables mapping from AST def_ids to
+        // LLVM-stuff-in-the-frame.
+
+        // Maps arguments to allocas created for them in llallocas.
+        hashmap[ast::node_id, ValueRef] llargs,
+
+        // Maps fields in objects to pointers into the interior of llself's
+        // body.
+        hashmap[ast::node_id, ValueRef] llobjfields,
+
+        // Maps the def_ids for local variables to the allocas created for
+        // them in llallocas.
+        hashmap[ast::node_id, ValueRef] lllocals,
+
+        // The same as above, but for variables accessed via the frame pointer
+        // we pass into an iter, for access to the static environment of the
+        // iter-calling frame.
+        hashmap[ast::node_id, ValueRef] llupvars,
+
+        // For convenience, a vector of the incoming tydescs for each of this
+        // functions type parameters, fetched via llvm::LLVMGetParam.  For
+        // example, for a function foo[A, B, C](), lltydescs contains the
+        // ValueRefs for the tydescs for A, B, and C.
+        mutable ValueRef[] lltydescs,
+
+        // Derived tydescs are tydescs created at runtime, for types that
+        // involve type parameters inside type constructors.  For example,
+        // suppose a function parameterized by T creates a vector of type
+        // [T].  The function doesn't know what T is until runtime, and the
+        // function's caller knows T but doesn't know that a vector is
+        // involved.  So a tydesc for [T] can't be created until runtime,
+        // when information about both "[T]" and "T" are available.  When such
+        // a tydesc is created, we cache it in the derived_tydescs table for
+        // the next time that such a tydesc is needed.
+        hashmap[ty::t, derived_tydesc_info] derived_tydescs,
+
+        // The source span where this function comes from, for error
+        // reporting.
+        span sp,
+
+        // This function's enclosing local context.
+        @local_ctxt lcx);
+
+tag cleanup {
+    clean(fn(&@block_ctxt) -> result);
+    clean_temp(ValueRef, fn(&@block_ctxt) -> result);
+}
+
+fn add_clean(&@block_ctxt cx, ValueRef val, ty::t ty) {
+    find_scope_cx(cx).cleanups += ~[clean(bind drop_slot(_, val, ty))];
+}
+fn add_clean_temp(&@block_ctxt cx, ValueRef val, ty::t ty) {
+    find_scope_cx(cx).cleanups += ~[clean_temp(val,
+                                               bind drop_ty(_, val, ty))];
+}
+
+// Note that this only works for temporaries. We should, at some point, move
+// to a system where we can also cancel the cleanup on local variables, but
+// this will be more involved. For now, we simply zero out the local, and the
+// drop glue checks whether it is zero.
+fn revoke_clean(&@block_ctxt cx, ValueRef val) {
+    auto sc_cx = find_scope_cx(cx);
+    auto found = -1;
+    auto i = 0;
+    for (cleanup c in sc_cx.cleanups) {
+        alt (c) {
+            case (clean_temp(?v, _)) {
+                if (v as uint == val as uint) { found = i; break; }
+            }
+            case (_) {}
+        }
+        i += 1;
+    }
+    // The value does not have a cleanup associated with it. Might be a
+    // constant or some immediate value.
+    if (found == -1) { ret; }
+    // We found the cleanup and remove it
+    sc_cx.cleanups = std::ivec::slice(sc_cx.cleanups, 0u, found as uint) +
+        std::ivec::slice(sc_cx.cleanups, found as uint + 1u,
+                         std::ivec::len(sc_cx.cleanups));
+}
+
+tag block_kind {
+
+    // A scope block is a basic block created by translating a block { ... }
+    // the the source language.  Since these blocks create variable scope, any
+    // variables created in them that are still live at the end of the block
+    // must be dropped and cleaned up when the block ends.
+    SCOPE_BLOCK;
+
+    // A basic block created from the body of a loop.  Contains pointers to
+    // which block to jump to in the case of "continue" or "break", with the
+    // "continue" block optional, because "while" and "do while" don't support
+    // "continue" (TODO: is this intentional?)
+    LOOP_SCOPE_BLOCK(option::t[@block_ctxt], @block_ctxt);
+
+    // A non-scope block is a basic block created as a translation artifact
+    // from translating code that expresses conditional logic rather than by
+    // explicit { ... } block structure in the source language.  It's called a
+    // non-scope block because it doesn't introduce a new variable scope.
+    NON_SCOPE_BLOCK;
+}
+
+
+// Basic block context.  We create a block context for each basic block
+// (single-entry, single-exit sequence of instructions) we generate from Rust
+// code.  Each basic block we generate is attached to a function, typically
+// with many basic blocks per function.  All the basic blocks attached to a
+// function are organized as a directed graph.
+type block_ctxt =
+    rec(
+        // The BasicBlockRef returned from a call to
+        // llvm::LLVMAppendBasicBlock(llfn, name), which adds a basic block to
+        // the function pointed to by llfn.  We insert instructions into that
+        // block by way of this block context.
+        BasicBlockRef llbb,
+
+        // The llvm::builder object serving as an interface to LLVM's
+        // LLVMBuild* functions.
+        builder build,
+
+        // The block pointing to this one in the function's digraph.
+        block_parent parent,
+
+        // The 'kind' of basic block this is.
+        block_kind kind,
+
+        // A list of functions that run at the end of translating this block,
+        // cleaning up any variables that were introduced in the block and
+        // need to go out of scope at the end of it.
+        mutable cleanup[] cleanups,
+
+        // The source span where this block comes from, for error reporting.
+        span sp,
+
+        // The function context for the function to which this block is
+        // attached.
+        @fn_ctxt fcx);
+
+// FIXME: we should be able to use option::t[@block_parent] here but
+// the infinite-tag check in rustboot gets upset.
+tag block_parent { parent_none; parent_some(@block_ctxt); }
+
+type result = rec(@block_ctxt bcx, ValueRef val);
+type result_t = rec(@block_ctxt bcx, ValueRef val, ty::t ty);
+
+fn extend_path(@local_ctxt cx, &str name) -> @local_ctxt {
+    ret @rec(path=cx.path + ~[name] with *cx);
+}
+
+fn rslt(@block_ctxt bcx, ValueRef val) -> result {
+    ret rec(bcx=bcx, val=val);
+}
+
+fn ty_str(type_names tn, TypeRef t) -> str {
+    ret lib::llvm::type_to_str(tn, t);
+}
+
+fn val_ty(ValueRef v) -> TypeRef { ret llvm::LLVMTypeOf(v); }
+
+fn val_str(type_names tn, ValueRef v) -> str { ret ty_str(tn, val_ty(v)); }
+
+// Returns the nth element of the given LLVM structure type.
+fn struct_elt(TypeRef llstructty, uint n) -> TypeRef {
+    auto elt_count = llvm::LLVMCountStructElementTypes(llstructty);
+    assert (n < elt_count);
+    auto elt_tys = std::ivec::init_elt(T_nil(), elt_count);
+    llvm::LLVMGetStructElementTypes(llstructty, std::ivec::to_ptr(elt_tys));
+    ret llvm::LLVMGetElementType(elt_tys.(n));
+}
+
+fn find_scope_cx(&@block_ctxt cx) -> @block_ctxt {
+    if (cx.kind != NON_SCOPE_BLOCK) { ret cx; }
+    alt (cx.parent) {
+        case (parent_some(?b)) { ret find_scope_cx(b); }
+        case (parent_none) {
+            cx.fcx.lcx.ccx.sess.bug("trans::find_scope_cx() " +
+                                        "called on parentless block_ctxt");
+        }
+    }
+}
+
+// Accessors
+// TODO: When we have overloading, simplify these names!
+
+fn bcx_tcx(&@block_ctxt bcx) -> ty::ctxt { ret bcx.fcx.lcx.ccx.tcx; }
+fn bcx_ccx(&@block_ctxt bcx) -> @crate_ctxt { ret bcx.fcx.lcx.ccx; }
+fn bcx_lcx(&@block_ctxt bcx) -> @local_ctxt { ret bcx.fcx.lcx; }
+fn bcx_fcx(&@block_ctxt bcx) -> @fn_ctxt { ret bcx.fcx; }
+fn lcx_ccx(&@local_ctxt lcx) -> @crate_ctxt { ret lcx.ccx; }
+fn ccx_tcx(&@crate_ctxt ccx) -> ty::ctxt { ret ccx.tcx; }
 
 // LLVM type constructors.
 fn T_void() -> TypeRef {
@@ -484,4 +833,3 @@ fn C_array(TypeRef ty, &ValueRef[] elts) -> ValueRef {
     ret llvm::LLVMConstArray(ty, std::ivec::to_ptr(elts),
                              std::ivec::len(elts));
 }
-
diff --git a/src/comp/middle/trans_dps.rs b/src/comp/middle/trans_dps.rs
index 25d349fdba9..f3d74ec4d3a 100644
--- a/src/comp/middle/trans_dps.rs
+++ b/src/comp/middle/trans_dps.rs
@@ -6,16 +6,12 @@ import back::link;
 import lib::llvm::llvm;
 import llvm::TypeRef;
 import llvm::ValueRef;
-import middle::trans;
+import middle::trans_common;
 import middle::ty;
 import syntax::ast;
 import syntax::codemap::span;
-import trans::block_ctxt;
-import trans::crate_ctxt;
-import trans::fn_ctxt;
-import trans::local_ctxt;
 import util::ppaux;
-
+import trans_common::*;
 import std::ivec;
 import std::option::none;
 import std::option::some;
@@ -25,7 +21,7 @@ import std::uint;
 import LLFalse = lib::llvm::False;
 import LLTrue = lib::llvm::True;
 import ll = lib::llvm;
-import lltype_of = trans::val_ty;
+import lltype_of = trans_common::val_ty;
 import option = std::option::t;
 import tc = trans_common;
 import type_of_node = trans::node_id_type;
@@ -47,7 +43,7 @@ fn llsize_of(&@crate_ctxt ccx, TypeRef llty) -> uint {
 
 fn mk_const(&@crate_ctxt ccx, &str name, bool exported, ValueRef llval)
         -> ValueRef {
-    auto llglobal = llvm::LLVMAddGlobal(ccx.llmod, trans::val_ty(llval),
+    auto llglobal = llvm::LLVMAddGlobal(ccx.llmod, tc::val_ty(llval),
                                         str::buf(name));
 
     llvm::LLVMSetInitializer(llglobal, llval);
@@ -140,23 +136,12 @@ fn dest_is_alias(&dest dest) -> bool {
 }
 
 
-// Accessors
-// TODO: When we have overloading, simplify these names!
-
-fn bcx_tcx(&@block_ctxt bcx) -> ty::ctxt { ret bcx.fcx.lcx.ccx.tcx; }
-fn bcx_ccx(&@block_ctxt bcx) -> @crate_ctxt { ret bcx.fcx.lcx.ccx; }
-fn bcx_lcx(&@block_ctxt bcx) -> @local_ctxt { ret bcx.fcx.lcx; }
-fn bcx_fcx(&@block_ctxt bcx) -> @fn_ctxt { ret bcx.fcx; }
-fn lcx_ccx(&@local_ctxt lcx) -> @crate_ctxt { ret lcx.ccx; }
-fn ccx_tcx(&@crate_ctxt ccx) -> ty::ctxt { ret ccx.tcx; }
-
-
 // Common operations
 
 fn memmove(&@block_ctxt bcx, ValueRef lldestptr, ValueRef llsrcptr,
            ValueRef llsz) {
-    auto lldestty = llelement_type(trans::val_ty(lldestptr));
-    auto llsrcty = llelement_type(trans::val_ty(llsrcptr));
+    auto lldestty = llelement_type(tc::val_ty(lldestptr));
+    auto llsrcty = llelement_type(tc::val_ty(llsrcptr));
     auto dest_align = llalign_of(bcx_ccx(bcx), lldestty);
     auto src_align = llalign_of(bcx_ccx(bcx), llsrcty);
     auto align = uint::min(dest_align, src_align);
@@ -205,7 +190,7 @@ fn store_ptr(&@block_ctxt bcx, &dest dest, ValueRef llsrcptr) -> @block_ctxt {
         *box = some(llsrcptr);
       }
       dst_copy(?lldestptr) | dst_move(?lldestptr) {
-        auto llsrcty = llelement_type(trans::val_ty(llsrcptr));
+        auto llsrcty = llelement_type(tc::val_ty(llsrcptr));
         auto llsz = tc::C_uint(llsize_of(bcx_ccx(bcx), llsrcty));
         memmove(bcx, lldestptr, llsrcptr, llsz);
         ret bcx;
@@ -421,7 +406,7 @@ fn trans_log(&@block_ctxt cx, &span sp, int level, &@ast::expr expr)
                        ~[bcx_fcx(bcx).lltaskptr, tc::C_int(level), llarg]);
 
     log_bcx = trans::trans_block_cleanups(log_bcx,
-                                          trans::find_scope_cx(log_bcx));
+                                          tc::find_scope_cx(log_bcx));
     log_bcx.build.Br(next_bcx.llbb);
     ret next_bcx;
 }
@@ -481,7 +466,7 @@ fn trans_block(&@block_ctxt cx, &dest dest, &ast::block block)
       none { /* no-op */ }
     }
 
-    bcx = trans::trans_block_cleanups(bcx, trans::find_scope_cx(bcx));
+    bcx = trans::trans_block_cleanups(bcx, tc::find_scope_cx(bcx));
     ret bcx;
 }
 
@@ -583,7 +568,7 @@ fn trans_init_local(&@block_ctxt bcx, &@ast::local local) -> @block_ctxt {
     auto llptr = bcx_fcx(bcx).lllocals.get(local.node.id);
 
     auto t = type_of_node(bcx_ccx(bcx), local.node.id);
-    trans::add_clean(bcx, llptr, t);
+    tc::add_clean(bcx, llptr, t);
 
     alt (local.node.init) {
       some(?init) {
diff --git a/src/comp/middle/trans_vec.rs b/src/comp/middle/trans_vec.rs
index 6d93b4cc392..1707c085869 100644
--- a/src/comp/middle/trans_vec.rs
+++ b/src/comp/middle/trans_vec.rs
@@ -10,11 +10,11 @@ import middle::ty;
 import syntax::ast;
 import syntax::codemap::span;
 import trans::alloca;
-import trans::block_ctxt;
 import trans::load_inbounds;
 import trans::new_sub_block_ctxt;
-import trans::struct_elt;
 import trans::type_of_or_i8;
+import trans_common::block_ctxt;
+import trans_common::struct_elt;
 import trans_common::C_int;
 import trans_common::C_null;
 import trans_common::C_uint;
@@ -23,8 +23,8 @@ import trans_common::T_ivec_heap;
 import trans_common::T_ivec_heap_part;
 import trans_common::T_opaque_ivec;
 import trans_common::T_ptr;
-import trans_dps::bcx_ccx;
-import trans_dps::bcx_tcx;
+import trans_common::bcx_ccx;
+import trans_common::bcx_tcx;
 import trans_dps::dest;
 import trans_dps::llsize_of;
 import trans_dps::mk_temp;