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rdar://13126763

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Fix a bug in DAGCombine. The symptom is mistakenly optimizing expression
"x + x*x" into "x * 3.0".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174239 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Shuxin Yang 2013-02-02 00:22:03 +00:00
parent 7650d9b893
commit 98b93e5a94
2 changed files with 62 additions and 13 deletions
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33
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -5832,13 +5832,6 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
N1, NewCFP);
}
// (fadd (fadd x, x), x) -> (fmul 3.0, x)
if (!CFP00 && !CFP01 && N0.getOperand(0) == N0.getOperand(1) &&
N0.getOperand(0) == N1) {
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT,
N1, DAG.getConstantFP(3.0, VT));
}
// (fadd (fmul c, x), (fadd x, x)) -> (fmul c+2, x)
if (CFP00 && !CFP01 && N1.getOpcode() == ISD::FADD &&
N1.getOperand(0) == N1.getOperand(1) &&
@ -5884,12 +5877,6 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
N0, NewCFP);
}
// (fadd x, (fadd x, x)) -> (fmul 3.0, x)
if (!CFP10 && !CFP11 && N1.getOperand(0) == N1.getOperand(1) &&
N1.getOperand(0) == N0) {
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT,
N0, DAG.getConstantFP(3.0, VT));
}
// (fadd (fadd x, x), (fmul c, x)) -> (fmul c+2, x)
if (CFP10 && !CFP11 && N1.getOpcode() == ISD::FADD &&
@ -5914,6 +5901,26 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
}
}
if (N0.getOpcode() == ISD::FADD) {
ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N0.getOperand(0));
// (fadd (fadd x, x), x) -> (fmul 3.0, x)
if (!CFP && N0.getOperand(0) == N0.getOperand(1) &&
(N0.getOperand(0) == N1)) {
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT,
N1, DAG.getConstantFP(3.0, VT));
}
}
if (N1.getOpcode() == ISD::FADD) {
ConstantFPSDNode *CFP10 = dyn_cast<ConstantFPSDNode>(N1.getOperand(0));
// (fadd x, (fadd x, x)) -> (fmul 3.0, x)
if (!CFP10 && N1.getOperand(0) == N1.getOperand(1) &&
N1.getOperand(0) == N0) {
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT,
N0, DAG.getConstantFP(3.0, VT));
}
}
// (fadd (fadd x, x), (fadd x, x)) -> (fmul 4.0, x)
if (N0.getOpcode() == ISD::FADD && N1.getOpcode() == ISD::FADD &&
N0.getOperand(0) == N0.getOperand(1) &&

42
test/CodeGen/X86/dagcombine_unsafe_math.ll Normal file
View File

@ -0,0 +1,42 @@
; RUN: llc < %s -enable-unsafe-fp-math -mtriple=x86_64-apple-darwin -mcpu=corei7-avx | FileCheck %s
; rdar://13126763
; Expression "x + x*x" was mistakenly transformed into "x * 3.0f".
define float @test1(float %x) {
%t1 = fmul fast float %x, %x
%t2 = fadd fast float %t1, %x
ret float %t2
; CHECK: test1
; CHECK: vaddss
}
; (x + x) + x => x * 3.0
define float @test2(float %x) {
%t1 = fadd fast float %x, %x
%t2 = fadd fast float %t1, %x
ret float %t2
; CHECK: .long 1077936128
; CHECK: test2
; CHECK: vmulss LCPI1_0(%rip), %xmm0, %xmm0
}
; x + (x + x) => x * 3.0
define float @test3(float %x) {
%t1 = fadd fast float %x, %x
%t2 = fadd fast float %t1, %x
ret float %t2
; CHECK: .long 1077936128
; CHECK: test3
; CHECK: vmulss LCPI2_0(%rip), %xmm0, %xmm0
}
; (y + x) + x != x * 3.0
define float @test4(float %x, float %y) {
%t1 = fadd fast float %x, %y
%t2 = fadd fast float %t1, %x
ret float %t2
; CHECK: test4
; CHECK: vaddss
}