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GlobalISel: avoid inserting redundant COPYs for bitcasts.

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If the value produced by the bitcast hasn't been referenced yet, we can simply
reuse the input register avoiding an unnecessary COPY instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278245 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2016-08-10 16:51:14 +00:00
parent 3b54bd1701
commit 6b89c9016c
2 changed files with 26 additions and 4 deletions
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7
lib/CodeGen/GlobalISel/IRTranslator.cpp
View File

@ -166,8 +166,11 @@ bool IRTranslator::translateStore(const StoreInst &SI) {
bool IRTranslator::translateBitCast(const CastInst &CI) {
if (LLT{*CI.getDestTy()} == LLT{*CI.getSrcTy()}) {
MIRBuilder.buildCopy(getOrCreateVReg(CI),
getOrCreateVReg(*CI.getOperand(0)));
unsigned &Reg = ValToVReg[&CI];
if (Reg)
MIRBuilder.buildCopy(Reg, getOrCreateVReg(*CI.getOperand(0)));
else
Reg = getOrCreateVReg(*CI.getOperand(0));
return true;
}
return translateCast(TargetOpcode::G_BITCAST, CI);

23
test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
View File

@ -214,14 +214,33 @@ define i64* @inttoptr(i64 %a) {
; CHECK-LABEL: name: trivial_bitcast
; CHECK: [[ARG1:%[0-9]+]](64) = COPY %x0
; CHECK: [[RES:%[0-9]+]](64) = COPY [[ARG1]]
; CHECK: %x0 = COPY [[RES]]
; CHECK: %x0 = COPY [[ARG1]]
; CHECK: RET_ReallyLR implicit %x0
define i64* @trivial_bitcast(i8* %a) {
%val = bitcast i8* %a to i64*
ret i64* %val
}
; CHECK-LABEL: name: trivial_bitcast_with_copy
; CHECK: [[A:%[0-9]+]](64) = COPY %x0
; CHECK: G_BR unsized %[[CAST:bb\.[0-9]+]]
; CHECK: [[CAST]]:
; CHECK: {{%[0-9]+}}(64) = COPY [[A]]
; CHECK: G_BR unsized %[[END:bb\.[0-9]+]]
; CHECK: [[END]]:
define i64* @trivial_bitcast_with_copy(i8* %a) {
br label %cast
end:
ret i64* %val
cast:
%val = bitcast i8* %a to i64*
br label %end
}
; CHECK-LABEL: name: bitcast
; CHECK: [[ARG1:%[0-9]+]](64) = COPY %x0
; CHECK: [[RES1:%[0-9]+]](64) = G_BITCAST { <2 x s32>, s64 } [[ARG1]]