mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-12-09 04:24:10 +00:00
[CodeGen] Ignore return sext/zext attributes of unused results for tail calls
If the caller's return type does not have a zeroext attribute but the callee does a tail call zeroext, we won't consider the tail call during CodeGenPrepare because the attributes don't match. However, if the result of the tail call has no uses, it makes sense to drop the sext/zext attributes. Differential Revision: https://reviews.llvm.org/D56486 llvm-svn: 350753
This commit is contained in:
parent
372b240afa
commit
3a33d73f69
@ -546,6 +546,21 @@ bool llvm::attributesPermitTailCall(const Function *F, const Instruction *I,
|
||||
CalleeAttrs.removeAttribute(Attribute::SExt);
|
||||
}
|
||||
|
||||
// Drop sext and zext return attributes if the result is not used.
|
||||
// This enables tail calls for code like:
|
||||
//
|
||||
// define void @caller() {
|
||||
// entry:
|
||||
// %unused_result = tail call zeroext i1 @callee()
|
||||
// br label %retlabel
|
||||
// retlabel:
|
||||
// ret void
|
||||
// }
|
||||
if (I->use_empty()) {
|
||||
CalleeAttrs.removeAttribute(Attribute::SExt);
|
||||
CalleeAttrs.removeAttribute(Attribute::ZExt);
|
||||
}
|
||||
|
||||
// If they're still different, there's some facet we don't understand
|
||||
// (currently only "inreg", but in future who knows). It may be OK but the
|
||||
// only safe option is to reject the tail call.
|
||||
|
36
test/CodeGen/AArch64/tail-call-unused-zext.ll
Normal file
36
test/CodeGen/AArch64/tail-call-unused-zext.ll
Normal file
@ -0,0 +1,36 @@
|
||||
; RUN: llc -mtriple=arm64--- -stop-after=expand-isel-pseudos -o - %s | FileCheck %s
|
||||
|
||||
; Check that we ignore the zeroext attribute on the return type of the tail
|
||||
; call, since the return value is unused. This happens during CodeGenPrepare in
|
||||
; dupRetToEnableTailCallOpts, which calls attributesPermitTailCall to check if
|
||||
; the attributes of the caller and the callee match.
|
||||
|
||||
declare zeroext i1 @zcallee()
|
||||
define void @zcaller() {
|
||||
; CHECK-LABEL: name: zcaller
|
||||
entry:
|
||||
br i1 undef, label %calllabel, label %retlabel
|
||||
calllabel:
|
||||
; CHECK: bb.1.calllabel:
|
||||
; CHECK-NOT: BL @zcallee
|
||||
; CHECK-NEXT: TCRETURNdi @zcallee
|
||||
%unused_result = tail call zeroext i1 @zcallee()
|
||||
br label %retlabel
|
||||
retlabel:
|
||||
ret void
|
||||
}
|
||||
|
||||
declare signext i1 @scallee()
|
||||
define void @scaller() {
|
||||
; CHECK-LABEL: name: scaller
|
||||
entry:
|
||||
br i1 undef, label %calllabel, label %retlabel
|
||||
calllabel:
|
||||
; CHECK: bb.1.calllabel:
|
||||
; CHECK-NOT: BL @scallee
|
||||
; CHECK-NEXT: TCRETURNdi @scallee
|
||||
%unused_result = tail call signext i1 @scallee()
|
||||
br label %retlabel
|
||||
retlabel:
|
||||
ret void
|
||||
}
|
Loading…
Reference in New Issue
Block a user