Add Minimal Std implementation for UEFI

Implemented modules:
1. alloc
2. os_str
3. env
4. math

Tracking Issue: https://github.com/rust-lang/rust/issues/100499
API Change Proposal: https://github.com/rust-lang/libs-team/issues/87

This was originally part of https://github.com/rust-lang/rust/pull/100316. Since
that PR was becoming too unwieldy and cluttered, and with suggestion
from @dvdhrm, I have extracted a minimal std implementation to this PR.

Signed-off-by: Ayush Singh <ayushsingh1325@gmail.com>

1 files changed, 28 insertions, 7 deletions

diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index cd19885faa0..4753f125540 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -420,9 +420,11 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         rust_main_def_id: DefId,
         entry_type: EntryFnType,
     ) -> Bx::Function {
-        // The entry function is either `int main(void)` or `int main(int argc, char **argv)`,
-        // depending on whether the target needs `argc` and `argv` to be passed in.
-        let llfty = if cx.sess().target.main_needs_argc_argv {
+        // The entry function is either `int main(void)` or `int main(int argc, char **argv)`, or
+        // `Status efi_main(Handle hd, SystemTable *st)` depending on the target.
+        let llfty = if cx.sess().target.os.contains("uefi") {
+            cx.type_func(&[cx.type_ptr(), cx.type_ptr()], cx.type_isize())
+        } else if cx.sess().target.main_needs_argc_argv {
             cx.type_func(&[cx.type_int(), cx.type_ptr()], cx.type_int())
         } else {
             cx.type_func(&[], cx.type_int())
@@ -485,8 +487,12 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         };
 
         let result = bx.call(start_ty, None, None, start_fn, &args, None);
-        let cast = bx.intcast(result, cx.type_int(), true);
-        bx.ret(cast);
+        if cx.sess().target.os.contains("uefi") {
+            bx.ret(result);
+        } else {
+            let cast = bx.intcast(result, cx.type_int(), true);
+            bx.ret(cast);
+        }
 
         llfn
     }
@@ -497,7 +503,18 @@ fn get_argc_argv<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     cx: &'a Bx::CodegenCx,
     bx: &mut Bx,
 ) -> (Bx::Value, Bx::Value) {
-    if cx.sess().target.main_needs_argc_argv {
+    if cx.sess().target.os.contains("uefi") {
+        // Params for UEFI
+        let param_handle = bx.get_param(0);
+        let param_system_table = bx.get_param(1);
+        let arg_argc = bx.const_int(cx.type_isize(), 2);
+        let arg_argv = bx.alloca(cx.type_array(cx.type_i8p(), 2), Align::ONE);
+        bx.store(param_handle, arg_argv, Align::ONE);
+        let arg_argv_el1 =
+            bx.gep(cx.type_ptr_to(cx.type_i8()), arg_argv, &[bx.const_int(cx.type_int(), 1)]);
+        bx.store(param_system_table, arg_argv_el1, Align::ONE);
+        (arg_argc, arg_argv)
+    } else if cx.sess().target.main_needs_argc_argv {
         // Params from native `main()` used as args for rust start function
         let param_argc = bx.get_param(0);
         let param_argv = bx.get_param(1);
@@ -549,7 +566,11 @@ pub fn allocator_kind_for_codegen(tcx: TyCtxt<'_>) -> Option<AllocatorKind> {
         use rustc_middle::middle::dependency_format::Linkage;
         list.iter().any(|&linkage| linkage == Linkage::Dynamic)
     });
-    if any_dynamic_crate { None } else { tcx.allocator_kind(()) }
+    if any_dynamic_crate {
+        None
+    } else {
+        tcx.allocator_kind(())
+    }
 }
 
 pub fn codegen_crate<B: ExtraBackendMethods>(