Auto merge of #76071 - khyperia:configurable_to_immediate, r=eddyb

Make to_immediate/from_immediate configurable by backends

`librustc_codegen_ssa` has the concept of an immediate vs. memory type, and `librustc_codegen_llvm` uses this distinction to implement `bool`s being `i8` in memory, and `i1` in immediate contexts. However, some of that implementation leaked into `codegen_ssa` when converting to/from immediate values. So, move those methods into builder traits, so that behavior can be configured by backends.

This is useful if a backend is able to keep bools as bools, or, needs to do more trickery than just bools to bytes.

(Note that there's already a large amount of things abstracted with "immediate types" - this is just bringing this particular thing in line to be abstracted as well)

---

Pinging @eddyb since that's who I was talking about this change with when they suggested I submit a PR.

7 files changed, 56 insertions, 68 deletions

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 4ece08f6293..89c3e21632e 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -6,7 +6,6 @@ use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 use libc::{c_char, c_uint};
-use rustc_codegen_ssa::base::to_immediate;
 use rustc_codegen_ssa::common::{IntPredicate, RealPredicate, TypeKind};
 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
 use rustc_codegen_ssa::mir::place::PlaceRef;
@@ -367,6 +366,20 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         (self.extract_value(res, 0), self.extract_value(res, 1))
     }
 
+    fn from_immediate(&mut self, val: Self::Value) -> Self::Value {
+        if self.cx().val_ty(val) == self.cx().type_i1() {
+            self.zext(val, self.cx().type_i8())
+        } else {
+            val
+        }
+    }
+    fn to_immediate_scalar(&mut self, val: Self::Value, scalar: &abi::Scalar) -> Self::Value {
+        if scalar.is_bool() {
+            return self.trunc(val, self.cx().type_i1());
+        }
+        val
+    }
+
     fn alloca(&mut self, ty: &'ll Type, align: Align) -> &'ll Value {
         let mut bx = Builder::with_cx(self.cx);
         bx.position_at_start(unsafe { llvm::LLVMGetFirstBasicBlock(self.llfn()) });
@@ -471,7 +484,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 }
                 load
             });
-            OperandValue::Immediate(to_immediate(self, llval, place.layout))
+            OperandValue::Immediate(self.to_immediate(llval, place.layout))
         } else if let abi::Abi::ScalarPair(ref a, ref b) = place.layout.abi {
             let b_offset = a.value.size(self).align_to(b.value.align(self).abi);
 
@@ -479,7 +492,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 let llptr = self.struct_gep(place.llval, i as u64);
                 let load = self.load(llptr, align);
                 scalar_load_metadata(self, load, scalar);
-                if scalar.is_bool() { self.trunc(load, self.type_i1()) } else { load }
+                self.to_immediate_scalar(load, scalar)
             };
 
             OperandValue::Pair(
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index c1dfb83b135..951b9928cc9 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -8,7 +8,7 @@ use crate::va_arg::emit_va_arg;
 use crate::value::Value;
 
 use rustc_ast as ast;
-use rustc_codegen_ssa::base::{compare_simd_types, to_immediate, wants_msvc_seh};
+use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh};
 use rustc_codegen_ssa::common::span_invalid_monomorphization_error;
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc_codegen_ssa::glue;
@@ -301,7 +301,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 unsafe {
                     llvm::LLVMSetAlignment(load, align);
                 }
-                to_immediate(self, load, self.layout_of(tp_ty))
+                self.to_immediate(load, self.layout_of(tp_ty))
             }
             sym::volatile_store => {
                 let dst = args[0].deref(self.cx());
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 77c12c410d5..e0b649d91c7 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -38,7 +38,7 @@ use rustc_middle::middle::cstore::EncodedMetadata;
 use rustc_middle::middle::cstore::{self, LinkagePreference};
 use rustc_middle::middle::lang_items;
 use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem};
-use rustc_middle::ty::layout::{self, HasTyCtxt, TyAndLayout};
+use rustc_middle::ty::layout::{HasTyCtxt, TyAndLayout};
 use rustc_middle::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
@@ -48,7 +48,7 @@ use rustc_session::utils::NativeLibKind;
 use rustc_session::Session;
 use rustc_span::Span;
 use rustc_symbol_mangling::test as symbol_names_test;
-use rustc_target::abi::{Abi, Align, LayoutOf, Scalar, VariantIdx};
+use rustc_target::abi::{Align, LayoutOf, VariantIdx};
 
 use std::cmp;
 use std::ops::{Deref, DerefMut};
@@ -330,35 +330,6 @@ pub fn wants_msvc_seh(sess: &Session) -> bool {
     sess.target.target.options.is_like_msvc
 }
 
-pub fn from_immediate<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
-    bx: &mut Bx,
-    val: Bx::Value,
-) -> Bx::Value {
-    if bx.cx().val_ty(val) == bx.cx().type_i1() { bx.zext(val, bx.cx().type_i8()) } else { val }
-}
-
-pub fn to_immediate<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
-    bx: &mut Bx,
-    val: Bx::Value,
-    layout: layout::TyAndLayout<'_>,
-) -> Bx::Value {
-    if let Abi::Scalar(ref scalar) = layout.abi {
-        return to_immediate_scalar(bx, val, scalar);
-    }
-    val
-}
-
-pub fn to_immediate_scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
-    bx: &mut Bx,
-    val: Bx::Value,
-    scalar: &Scalar,
-) -> Bx::Value {
-    if scalar.is_bool() {
-        return bx.trunc(val, bx.cx().type_i1());
-    }
-    val
-}
-
 pub fn memcpy_ty<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx: &mut Bx,
     dst: Bx::Value,
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 8048a569f79..6eb80157239 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -1143,7 +1143,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
                 }
                 // We store bools as `i8` so we need to truncate to `i1`.
-                llval = base::to_immediate(bx, llval, arg.layout);
+                llval = bx.to_immediate(llval, arg.layout);
             }
         }
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs
index 937c7457c63..bbd004be875 100644
--- a/compiler/rustc_codegen_ssa/src/mir/operand.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs
@@ -147,8 +147,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
             debug!("Operand::immediate_or_packed_pair: packing {:?} into {:?}", self, llty);
             // Reconstruct the immediate aggregate.
             let mut llpair = bx.cx().const_undef(llty);
-            let imm_a = base::from_immediate(bx, a);
-            let imm_b = base::from_immediate(bx, b);
+            let imm_a = bx.from_immediate(a);
+            let imm_b = bx.from_immediate(b);
             llpair = bx.insert_value(llpair, imm_a, 0);
             llpair = bx.insert_value(llpair, imm_b, 1);
             llpair
@@ -168,9 +168,9 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
 
             // Deconstruct the immediate aggregate.
             let a_llval = bx.extract_value(llval, 0);
-            let a_llval = base::to_immediate_scalar(bx, a_llval, a);
+            let a_llval = bx.to_immediate_scalar(a_llval, a);
             let b_llval = bx.extract_value(llval, 1);
-            let b_llval = base::to_immediate_scalar(bx, b_llval, b);
+            let b_llval = bx.to_immediate_scalar(b_llval, b);
             OperandValue::Pair(a_llval, b_llval)
         } else {
             OperandValue::Immediate(llval)
@@ -220,29 +220,23 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
             _ => bug!("OperandRef::extract_field({:?}): not applicable", self),
         };
 
-        // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
-        // Bools in union fields needs to be truncated.
-        let to_immediate_or_cast = |bx: &mut Bx, val, ty| {
-            if ty == bx.cx().type_i1() { bx.trunc(val, ty) } else { bx.bitcast(val, ty) }
-        };
-
-        match val {
-            OperandValue::Immediate(ref mut llval) => {
-                *llval = to_immediate_or_cast(bx, *llval, bx.cx().immediate_backend_type(field));
+        match (&mut val, &field.abi) {
+            (OperandValue::Immediate(llval), _) => {
+                // Bools in union fields needs to be truncated.
+                *llval = bx.to_immediate(*llval, field);
+                // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
+                *llval = bx.bitcast(*llval, bx.cx().immediate_backend_type(field));
             }
-            OperandValue::Pair(ref mut a, ref mut b) => {
-                *a = to_immediate_or_cast(
-                    bx,
-                    *a,
-                    bx.cx().scalar_pair_element_backend_type(field, 0, true),
-                );
-                *b = to_immediate_or_cast(
-                    bx,
-                    *b,
-                    bx.cx().scalar_pair_element_backend_type(field, 1, true),
-                );
+            (OperandValue::Pair(a, b), Abi::ScalarPair(a_abi, b_abi)) => {
+                // Bools in union fields needs to be truncated.
+                *a = bx.to_immediate_scalar(*a, a_abi);
+                *b = bx.to_immediate_scalar(*b, b_abi);
+                // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
+                *a = bx.bitcast(*a, bx.cx().scalar_pair_element_backend_type(field, 0, true));
+                *b = bx.bitcast(*b, bx.cx().scalar_pair_element_backend_type(field, 1, true));
             }
-            OperandValue::Ref(..) => bug!(),
+            (OperandValue::Pair(..), _) => bug!(),
+            (OperandValue::Ref(..), _) => bug!(),
         }
 
         OperandRef { val, layout: field }
@@ -302,7 +296,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
                 bug!("cannot directly store unsized values");
             }
             OperandValue::Immediate(s) => {
-                let val = base::from_immediate(bx, s);
+                let val = bx.from_immediate(s);
                 bx.store_with_flags(val, dest.llval, dest.align, flags);
             }
             OperandValue::Pair(a, b) => {
@@ -313,12 +307,12 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
                 let b_offset = a_scalar.value.size(bx).align_to(b_scalar.value.align(bx).abi);
 
                 let llptr = bx.struct_gep(dest.llval, 0);
-                let val = base::from_immediate(bx, a);
+                let val = bx.from_immediate(a);
                 let align = dest.align;
                 bx.store_with_flags(val, llptr, align, flags);
 
                 let llptr = bx.struct_gep(dest.llval, 1);
-                let val = base::from_immediate(bx, b);
+                let val = bx.from_immediate(b);
                 let align = dest.align.restrict_for_offset(b_offset);
                 bx.store_with_flags(val, llptr, align, flags);
             }
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 71f924df119..1994c45707c 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -98,7 +98,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
 
                     // Use llvm.memset.p0i8.* to initialize byte arrays
-                    let v = base::from_immediate(&mut bx, v);
+                    let v = bx.from_immediate(v);
                     if bx.cx().val_ty(v) == bx.cx().type_i8() {
                         bx.memset(start, v, size, dest.align, MemFlags::empty());
                         return bx;
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index 5ffc83c5f99..5142922260a 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -13,9 +13,9 @@ use crate::mir::operand::OperandRef;
 use crate::mir::place::PlaceRef;
 use crate::MemFlags;
 
-use rustc_middle::ty::layout::HasParamEnv;
+use rustc_middle::ty::layout::{HasParamEnv, TyAndLayout};
 use rustc_middle::ty::Ty;
-use rustc_target::abi::{Align, Size};
+use rustc_target::abi::{Abi, Align, Scalar, Size};
 use rustc_target::spec::HasTargetSpec;
 
 use std::iter::TrustedLen;
@@ -115,6 +115,16 @@ pub trait BuilderMethods<'a, 'tcx>:
         rhs: Self::Value,
     ) -> (Self::Value, Self::Value);
 
+    fn from_immediate(&mut self, val: Self::Value) -> Self::Value;
+    fn to_immediate(&mut self, val: Self::Value, layout: TyAndLayout<'_>) -> Self::Value {
+        if let Abi::Scalar(ref scalar) = layout.abi {
+            self.to_immediate_scalar(val, scalar)
+        } else {
+            val
+        }
+    }
+    fn to_immediate_scalar(&mut self, val: Self::Value, scalar: &Scalar) -> Self::Value;
+
     fn alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
     fn dynamic_alloca(&mut self, ty: Self::Type, align: Align) -> Self::Value;
     fn array_alloca(&mut self, ty: Self::Type, len: Self::Value, align: Align) -> Self::Value;