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Constant fold launder of null and undef 

Summary:
This might be useful because clang will add
some barriers for pointer comparisons.

Reviewers: majnemer, dberlin, hfinkel, nlewycky, davide, rsmith, amharc,
kuhar

Subscribers: davide, amharc, llvm-commits

Differential Revision: https://reviews.llvm.org/D32423

llvm-svn: 332786
This commit is contained in:
Piotr Padlewski 2018-05-18 23:52:57 +00:00
parent dbb6f8a817
commit a26a08cb52
3 changed files with 49 additions and 3 deletions
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13
llvm/lib/Analysis/ConstantFolding.cpp
View File

@ -1392,6 +1392,7 @@ bool llvm::canConstantFoldCallTo(ImmutableCallSite CS, const Function *F) {
case Intrinsic::fma:
case Intrinsic::fmuladd:
case Intrinsic::copysign:
case Intrinsic::launder_invariant_group:
case Intrinsic::round:
case Intrinsic::masked_load:
case Intrinsic::sadd_with_overflow:
@ -1594,9 +1595,19 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
if (IntrinsicID == Intrinsic::cos)
return Constant::getNullValue(Ty);
if (IntrinsicID == Intrinsic::bswap ||
IntrinsicID == Intrinsic::bitreverse)
IntrinsicID == Intrinsic::bitreverse ||
IntrinsicID == Intrinsic::launder_invariant_group)
return Operands[0];
}
if (isa<ConstantPointerNull>(Operands[0]) &&
Operands[0]->getType()->getPointerAddressSpace() == 0) {
// launder(null) == null iff in addrspace 0
if (IntrinsicID == Intrinsic::launder_invariant_group)
return Operands[0];
return nullptr;
}
if (auto *Op = dyn_cast<ConstantFP>(Operands[0])) {
if (IntrinsicID == Intrinsic::convert_to_fp16) {
APFloat Val(Op->getValueAPF());

5
llvm/lib/Transforms/Utils/Local.cpp
View File

@ -384,8 +384,9 @@ bool llvm::wouldInstructionBeTriviallyDead(Instruction *I,
// Special case intrinsics that "may have side effects" but can be deleted
// when dead.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
// Safe to delete llvm.stacksave if dead.
if (II->getIntrinsicID() == Intrinsic::stacksave)
// Safe to delete llvm.stacksave and launder.invariant.group if dead.
if (II->getIntrinsicID() == Intrinsic::stacksave ||
II->getIntrinsicID() == Intrinsic::launder_invariant_group)
return true;
// Lifetime intrinsics are dead when their right-hand is undef.

34
llvm/test/Transforms/InstCombine/invariant.group.ll Normal file
View File

@ -0,0 +1,34 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; CHECK-LABEL: define i8* @simplifyNullLaunder()
define i8* @simplifyNullLaunder() {
; CHECK-NEXT: ret i8* null
%b2 = call i8* @llvm.launder.invariant.group.p0i8(i8* null)
ret i8* %b2
}
; CHECK-LABEL: define i8 addrspace(42)* @dontsimplifyNullLaunderForDifferentAddrspace()
define i8 addrspace(42)* @dontsimplifyNullLaunderForDifferentAddrspace() {
; CHECK: %b2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* null)
; CHECK: ret i8 addrspace(42)* %b2
%b2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* null)
ret i8 addrspace(42)* %b2
}
; CHECK-LABEL: define i8* @simplifyUndefLaunder()
define i8* @simplifyUndefLaunder() {
; CHECK-NEXT: ret i8* undef
%b2 = call i8* @llvm.launder.invariant.group.p0i8(i8* undef)
ret i8* %b2
}
; CHECK-LABEL: define i8 addrspace(42)* @simplifyUndefLaunder2()
define i8 addrspace(42)* @simplifyUndefLaunder2() {
; CHECK-NEXT: ret i8 addrspace(42)* undef
%b2 = call i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)* undef)
ret i8 addrspace(42)* %b2
}
declare i8* @llvm.launder.invariant.group.p0i8(i8*)
declare i8 addrspace(42)* @llvm.launder.invariant.group.p42i8(i8 addrspace(42)*)