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Teach DAG combine a number of tricks to simplify FMA expressions in fast-math mode. 

llvm-svn: 163051
This commit is contained in:
Owen Anderson 2012-09-01 06:04:27 +00:00
parent cdf814900d
commit 90e0eaffa8
2 changed files with 124 additions and 0 deletions
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64
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -5988,6 +5988,7 @@ SDValue DAGCombiner::visitFMA(SDNode *N) {
ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(N0);
ConstantFPSDNode *N1CFP = dyn_cast<ConstantFPSDNode>(N1);
EVT VT = N->getValueType(0);
DebugLoc dl = N->getDebugLoc();
if (N0CFP && N0CFP->isExactlyValue(1.0))
return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N1, N2);
@ -5998,6 +5999,58 @@ SDValue DAGCombiner::visitFMA(SDNode *N) {
if (N0CFP && !N1CFP)
return DAG.getNode(ISD::FMA, N->getDebugLoc(), VT, N1, N0, N2);
// (fma x, c1, (fmul x, c2)) -> (fmul x, c1+c2)
if (DAG.getTarget().Options.UnsafeFPMath && N1CFP &&
N2.getOpcode() == ISD::FMUL &&
N0 == N2.getOperand(0) &&
N2.getOperand(1).getOpcode() == ISD::ConstantFP) {
return DAG.getNode(ISD::FMUL, dl, VT, N0,
DAG.getNode(ISD::FADD, dl, VT, N1, N2.getOperand(1)));
}
// (fma (fmul x, c1), c2, y) -> (fma x, c1*c2, y)
if (DAG.getTarget().Options.UnsafeFPMath &&
N0.getOpcode() == ISD::FMUL && N1CFP &&
N0.getOperand(1).getOpcode() == ISD::ConstantFP) {
return DAG.getNode(ISD::FMA, dl, VT,
N0.getOperand(0),
DAG.getNode(ISD::FMUL, dl, VT, N1, N0.getOperand(1)),
N2);
}
// (fma x, 1, y) -> (fadd x, y)
// (fma x, -1, y) -> (fadd (fneg x), y)
if (N1CFP) {
if (N1CFP->isExactlyValue(1.0))
return DAG.getNode(ISD::FADD, dl, VT, N0, N2);
if (N1CFP->isExactlyValue(-1.0) &&
(!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))) {
SDValue RHSNeg = DAG.getNode(ISD::FNEG, dl, VT, N0);
AddToWorkList(RHSNeg.getNode());
return DAG.getNode(ISD::FADD, dl, VT, N2, RHSNeg);
}
}
// (fma x, c, x) -> (fmul x, (c+1))
if (DAG.getTarget().Options.UnsafeFPMath && N1CFP && N0 == N2) {
return DAG.getNode(ISD::FMUL, dl, VT,
N0,
DAG.getNode(ISD::FADD, dl, VT,
N1, DAG.getConstantFP(1.0, VT)));
}
// (fma x, c, (fneg x)) -> (fmul x, (c-1))
if (DAG.getTarget().Options.UnsafeFPMath && N1CFP &&
N2.getOpcode() == ISD::FNEG && N2.getOperand(0) == N0) {
return DAG.getNode(ISD::FMUL, dl, VT,
N0,
DAG.getNode(ISD::FADD, dl, VT,
N1, DAG.getConstantFP(-1.0, VT)));
}
return SDValue();
}
@ -6367,6 +6420,17 @@ SDValue DAGCombiner::visitFNEG(SDNode *N) {
}
}
// (fneg (fmul c, x)) -> (fmul -c, x)
if (N0.getOpcode() == ISD::FMUL) {
ConstantFPSDNode *CFP1 = dyn_cast<ConstantFPSDNode>(N0.getOperand(1));
if (CFP1) {
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT,
N0.getOperand(0),
DAG.getNode(ISD::FNEG, N->getDebugLoc(), VT,
N0.getOperand(1)));
}
}
return SDValue();
}

60
llvm/test/CodeGen/ARM/fp-fast.ll Normal file
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@ -0,0 +1,60 @@
; RUN: llc -march=arm -mcpu=cortex-a9 -mattr=+vfp4 -enable-unsafe-fp-math < %s | FileCheck %s
; CHECK: test1
define float @test1(float %x) {
; CHECK-NOT: vfma
; CHECK: vmul.f32
; CHECK-NOT: vfma
%t1 = fmul float %x, 3.0
%t2 = call float @llvm.fma.f32(float %x, float 2.0, float %t1)
ret float %t2
}
; CHECK: test2
define float @test2(float %x, float %y) {
; CHECK-NOT: vmul
; CHECK: vfma.f32
; CHECK-NOT: vmul
%t1 = fmul float %x, 3.0
%t2 = call float @llvm.fma.f32(float %t1, float 2.0, float %y)
ret float %t2
}
; CHECK: test3
define float @test3(float %x, float %y) {
; CHECK-NOT: vfma
; CHECK: vadd.f32
; CHECK-NOT: vfma
%t2 = call float @llvm.fma.f32(float %x, float 1.0, float %y)
ret float %t2
}
; CHECK: test4
define float @test4(float %x, float %y) {
; CHECK-NOT: vfma
; CHECK: vsub.f32
; CHECK-NOT: vfma
%t2 = call float @llvm.fma.f32(float %x, float -1.0, float %y)
ret float %t2
}
; CHECK: test5
define float @test5(float %x) {
; CHECK-NOT: vfma
; CHECK: vmul.f32
; CHECK-NOT: vfma
%t2 = call float @llvm.fma.f32(float %x, float 2.0, float %x)
ret float %t2
}
; CHECK: test6
define float @test6(float %x) {
; CHECK-NOT: vfma
; CHECK: vmul.f32
; CHECK-NOT: vfma
%t1 = fsub float -0.0, %x
%t2 = call float @llvm.fma.f32(float %x, float 5.0, float %t1)
ret float %t2
}
declare float @llvm.fma.f32(float, float, float)