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atomicrmw on pointers: move integer-pointer cast hacks into backend

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This commit is contained in:
Ralf Jung
2025-07-19 23:23:40 +02:00
parent efcae7d31d
commit de1b999ff6
17 changed files with 243 additions and 176 deletions
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14
compiler/rustc_codegen_llvm/src/builder.rs
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@@ -1326,15 +1326,13 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
&mut self,
op: rustc_codegen_ssa::common::AtomicRmwBinOp,
dst: &'ll Value,
mut src: &'ll Value,
src: &'ll Value,
order: rustc_middle::ty::AtomicOrdering,
ret_ptr: bool,
) -> &'ll Value {
// The only RMW operation that LLVM supports on pointers is compare-exchange.
let requires_cast_to_int = self.val_ty(src) == self.type_ptr()
&& op != rustc_codegen_ssa::common::AtomicRmwBinOp::AtomicXchg;
if requires_cast_to_int {
src = self.ptrtoint(src, self.type_isize());
}
// FIXME: If `ret_ptr` is true and `src` is not a pointer, we *should* tell LLVM that the
// LHS is a pointer and the operation should be provenance-preserving, but LLVM does not
// currently support that (https://github.com/llvm/llvm-project/issues/120837).
let mut res = unsafe {
llvm::LLVMBuildAtomicRMW(
self.llbuilder,
@@ -1345,7 +1343,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
llvm::False, // SingleThreaded
)
};
if requires_cast_to_int {
if ret_ptr && self.val_ty(res) != self.type_ptr() {
res = self.inttoptr(res, self.type_ptr());
}
res