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Set writable and dead_on_unwind attributes for sret arguments
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nikic committed Feb 23, 2024
1 parent dda102c commit d0544fb
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Showing 6 changed files with 30 additions and 2 deletions.
13 changes: 13 additions & 0 deletions compiler/rustc_codegen_llvm/src/abi.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ use crate::attributes;
use crate::builder::Builder;
use crate::context::CodegenCx;
use crate::llvm::{self, Attribute, AttributePlace};
use crate::llvm_util;
use crate::type_::Type;
use crate::type_of::LayoutLlvmExt;
use crate::value::Value;
Expand Down Expand Up @@ -426,6 +427,18 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
let i = apply(attrs);
let sret = llvm::CreateStructRetAttr(cx.llcx, self.ret.layout.llvm_type(cx));
attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[sret]);
if cx.sess().opts.optimize != config::OptLevel::No
&& llvm_util::get_version() >= (18, 0, 0)
{
attributes::apply_to_llfn(
llfn,
llvm::AttributePlace::Argument(i),
&[
llvm::AttributeKind::Writable.create_attr(cx.llcx),
llvm::AttributeKind::DeadOnUnwind.create_attr(cx.llcx),
],
);
}
}
PassMode::Cast { cast, pad_i32: _ } => {
cast.attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
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2 changes: 2 additions & 0 deletions compiler/rustc_codegen_llvm/src/llvm/ffi.rs
Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,8 @@ pub enum AttributeKind {
AllocAlign = 39,
SanitizeSafeStack = 40,
FnRetThunkExtern = 41,
Writable = 42,
DeadOnUnwind = 43,
}

/// LLVMIntPredicate
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2 changes: 2 additions & 0 deletions compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,8 @@ enum LLVMRustAttribute {
AllocAlign = 39,
SanitizeSafeStack = 40,
FnRetThunkExtern = 41,
Writable = 42,
DeadOnUnwind = 43,
};

typedef struct OpaqueRustString *RustStringRef;
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10 changes: 10 additions & 0 deletions compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -278,6 +278,16 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
return Attribute::SafeStack;
case FnRetThunkExtern:
return Attribute::FnRetThunkExtern;
#if LLVM_VERSION_GE(18, 0)
case Writable:
return Attribute::Writable;
case DeadOnUnwind:
return Attribute::DeadOnUnwind;
#else
case Writable:
case DeadOnUnwind:
report_fatal_error("Not supported on this LLVM version");
#endif
}
report_fatal_error("bad AttributeKind");
}
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2 changes: 1 addition & 1 deletion tests/codegen/function-arguments.rs
Original file line number Diff line number Diff line change
Expand Up @@ -188,7 +188,7 @@ pub fn notunpin_box(x: Box<NotUnpin>) -> Box<NotUnpin> {
x
}

// CHECK: @struct_return(ptr noalias nocapture noundef sret(%S) align 4 dereferenceable(32){{( %_0)?}})
// CHECK: @struct_return(ptr{{( dead_on_unwind)?}} noalias nocapture noundef{{( writable)?}} sret(%S) align 4 dereferenceable(32){{( %_0)?}})
#[no_mangle]
pub fn struct_return() -> S {
S {
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3 changes: 2 additions & 1 deletion tests/codegen/maybeuninit-rvo.rs
Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
//@ compile-flags: -O
//@ min-llvm-version: 18
#![feature(c_unwind)]
#![crate_type = "lib"]

Expand All @@ -24,7 +25,7 @@ extern "C-unwind" {

pub fn new_from_uninit_unwind() -> Foo {
// CHECK-LABEL: new_from_uninit
// CHECK: call void @llvm.memcpy.
// CHECK-NOT: call void @llvm.memcpy.
let mut x = std::mem::MaybeUninit::uninit();
unsafe {
init_unwind(x.as_mut_ptr());
Expand Down

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