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[AMDGPU] [CodeGen] Fold negate llvm.amdgcn.class into test mask

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Implemented the transformation of xor (llvm.amdgcn.class x, mask), -1 into
llvm.amdgcn.class(x, ~mask). Added LIT tests as well.

Differential Revision: https://reviews.llvm.org/D104049
This commit is contained in:
Anshil Gandhi 2021-06-18 13:04:12 -06:00
parent 89f841e69b
commit 7f0aeb0ac8
2 changed files with 92 additions and 0 deletions
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26
lib/Target/AMDGPU/AMDGPUCodeGenPrepare.cpp
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@ -201,6 +201,7 @@ public:
AMDGPUCodeGenPrepare() : FunctionPass(ID) {}
bool visitFDiv(BinaryOperator &I);
bool visitXor(BinaryOperator &I);
bool visitInstruction(Instruction &I) { return false; }
bool visitBinaryOperator(BinaryOperator &I);
@ -808,6 +809,31 @@ bool AMDGPUCodeGenPrepare::visitFDiv(BinaryOperator &FDiv) {
return !!NewFDiv;
}
bool AMDGPUCodeGenPrepare::visitXor(BinaryOperator &I) {
// Match the Xor instruction, its type and its operands
IntrinsicInst *IntrinsicCall = dyn_cast<IntrinsicInst>(I.getOperand(0));
ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1));
if (!RHS || !IntrinsicCall || RHS->getSExtValue() != -1)
return visitBinaryOperator(I);
// Check if the Call is an intrinsic intruction to amdgcn_class intrinsic
// has only one use
if (IntrinsicCall->getIntrinsicID() != Intrinsic::amdgcn_class ||
!IntrinsicCall->hasOneUse())
return visitBinaryOperator(I);
// "Not" the second argument of the intrinsic call
ConstantInt *Arg = dyn_cast<ConstantInt>(IntrinsicCall->getOperand(1));
if (!Arg)
return visitBinaryOperator(I);
IntrinsicCall->setOperand(
1, ConstantInt::get(Arg->getType(), Arg->getZExtValue() ^ 0x3ff));
I.replaceAllUsesWith(IntrinsicCall);
I.eraseFromParent();
return true;
}
static bool hasUnsafeFPMath(const Function &F) {
Attribute Attr = F.getFnAttribute("unsafe-fp-math");
return Attr.getValueAsBool();

66
test/CodeGen/AMDGPU/amdgpu-codegenprepare-foldnegate.ll Normal file
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@ -0,0 +1,66 @@
; RUN: opt -mtriple=amdgcn-amd-amdhsa -amdgpu-codegenprepare -verify -S %s -o - | FileCheck %s
declare i1 @llvm.amdgcn.class.f32(float, i32) nounwind readnone
declare i1 @llvm.amdgcn.class.f64(double, i32) nounwind readnone
; Trivial case, xor instruction should be removed and
; the second argument of the intrinsic call should be
; bitwise-negated
; CHECK: @fold_negate_intrinsic_test_mask
; CHECK: %1 = call i1 @llvm.amdgcn.class.f32(float %x, i32 1018)
define i1 @fold_negate_intrinsic_test_mask(float %x) nounwind {
%1 = call i1 @llvm.amdgcn.class.f32(float %x, i32 5)
%2 = xor i1 %1, -1
ret i1 %2
}
; Trivial case, xor instruction should be removed and
; the second argument of the intrinsic call should be
; bitwise-negated
; CHECK: @fold_negate_intrinsic_test_mask_dbl
; CHECK: %1 = call i1 @llvm.amdgcn.class.f64(double %x, i32 1018)
define i1 @fold_negate_intrinsic_test_mask_dbl(double %x) nounwind {
%1 = call i1 @llvm.amdgcn.class.f64(double %x, i32 5)
%2 = xor i1 %1, -1
ret i1 %2
}
; Negative test: should not transform for variable test masks
; CHECK: @fold_negate_intrinsic_test_mask_neg_var
; CHECK: %[[X0:.*]] = alloca i32
; CHECK: %[[X1:.*]] = load i32, i32* %[[X0]]
; CHECK: call i1 @llvm.amdgcn.class.f32(float %x, i32 %[[X1]])
; CHECK: xor
define i1 @fold_negate_intrinsic_test_mask_neg_var(float %x) nounwind {
%1 = alloca i32
store i32 7, i32* %1
%2 = load i32, i32* %1
%3 = call i1 @llvm.amdgcn.class.f32(float %x, i32 %2)
%4 = xor i1 %3, -1
ret i1 %4
}
; Negative test: should not transform for multiple uses of the
; intrinsic returned value
; CHECK: @fold_negate_intrinsic_test_mask_neg_multiple_uses
; CHECK: %[[X1:.*]] = call i1 @llvm.amdgcn.class.f32(float %x, i32 7)
; CHECK: store i1 %[[X1]]
; CHECK: %[[X2:.*]] = xor i1 %[[X1]]
define i1 @fold_negate_intrinsic_test_mask_neg_multiple_uses(float %x) nounwind {
%y = alloca i1
%1 = call i1 @llvm.amdgcn.class.f32(float %x, i32 7)
%2 = xor i1 %1, -1
store i1 %1, i1* %y
%3 = xor i1 %1, -1
ret i1 %2
}
; Negative test: should not transform for a xor with no operand equal to -1
; CHECK: @fold_negate_intrinsic_test_mask_neg_one
; CHECK: %[[X0:.*]] = call i1 @llvm.amdgcn.class.f32(float %x, i32 7)
; CHECK: xor i1 %[[X0]], false
define i1 @fold_negate_intrinsic_test_mask_neg_one(float %x) nounwind {
%1 = call i1 @llvm.amdgcn.class.f32(float %x, i32 7)
%2 = xor i1 %1, false
ret i1 %2
}