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Don't spill operands onto the stack in naked functions

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Currently, the code spills operands onto the stack for the purpose of
debuginfo. However, naked functions can only contain an asm block. Therefore,
attempting to spill the operands on the stack is undefined behavior.

Fixes https://github.com/rust-lang/rust/issues/42779
cc https://github.com/rust-lang/rust/issues/32408
This commit is contained in:
Nathaniel McCallum 2020-08-11 14:09:39 -04:00
parent 0356bb9fbb
commit 050fb380aa
1 changed files with 8 additions and 0 deletions
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8
src/librustc_codegen_ssa/mir/debuginfo.rs
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@ -1,6 +1,7 @@
use crate::traits::*;
use rustc_hir::def_id::CrateNum;
use rustc_index::vec::IndexVec;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::mir;
use rustc_middle::ty;
use rustc_session::config::DebugInfo;
@ -216,6 +217,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
LocalRef::Operand(None) => return,
LocalRef::Operand(Some(operand)) => {
// Don't spill operands onto the stack in naked functions.
// See: https://github.com/rust-lang/rust/issues/42779
let attrs = bx.tcx().codegen_fn_attrs(self.instance.def_id());
if attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
return;
}
// "Spill" the value onto the stack, for debuginfo,
// without forcing non-debuginfo uses of the local
// to also load from the stack every single time.