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[InstCombine] fold fsub+fneg with fdiv/fmul between 

The backend already does this via isNegatibleForFree(),
but we may want to alter the fneg IR canonicalizations
that currently exist, so we need to try harder to fold
fneg in IR to avoid regressions.

llvm-svn: 367194
This commit is contained in:
Sanjay Patel 2019-07-28 17:10:06 +00:00
parent 2c8098374b
commit 99c57c6daf
2 changed files with 23 additions and 8 deletions
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15
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -1964,6 +1964,21 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
if (match(Op1, m_OneUse(m_FPExt(m_FNeg(m_Value(Y)))))) if (match(Op1, m_OneUse(m_FPExt(m_FNeg(m_Value(Y))))))
return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPExt(Y, Ty), &I); return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPExt(Y, Ty), &I);
// Similar to above, but look through fmul/fdiv of the negated value:
// Op0 - (-X * Y) --> Op0 + (X * Y)
// Op0 - (Y * -X) --> Op0 + (X * Y)
if (match(Op1, m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))))) {
Value *FMul = Builder.CreateFMulFMF(X, Y, &I);
return BinaryOperator::CreateFAddFMF(Op0, FMul, &I);
}
// Op0 - (-X / Y) --> Op0 + (X / Y)
// Op0 - (X / -Y) --> Op0 + (X / Y)
if (match(Op1, m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y)))) ||
match(Op1, m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))))) {
Value *FDiv = Builder.CreateFDivFMF(X, Y, &I);
return BinaryOperator::CreateFAddFMF(Op0, FDiv, &I);
}
// Handle special cases for FSub with selects feeding the operation // Handle special cases for FSub with selects feeding the operation
if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1)) if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1))
return replaceInstUsesWith(I, V); return replaceInstUsesWith(I, V);

16
llvm/test/Transforms/InstCombine/fsub.ll
View File

@ -518,8 +518,8 @@ define float @fsub_fdiv_fneg1_extra_use2(float %x, float %y, float %z) {
; CHECK-LABEL: @fsub_fdiv_fneg1_extra_use2( ; CHECK-LABEL: @fsub_fdiv_fneg1_extra_use2(
; CHECK-NEXT: [[NEG:%.*]] = fsub float -0.000000e+00, [[X:%.*]] ; CHECK-NEXT: [[NEG:%.*]] = fsub float -0.000000e+00, [[X:%.*]]
; CHECK-NEXT: call void @use(float [[NEG]]) ; CHECK-NEXT: call void @use(float [[NEG]])
; CHECK-NEXT: [[DIV:%.*]] = fdiv float [[NEG]], [[Y:%.*]] ; CHECK-NEXT: [[TMP1:%.*]] = fdiv float [[X]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = fsub float [[Z:%.*]], [[DIV]] ; CHECK-NEXT: [[R:%.*]] = fadd float [[TMP1]], [[Z:%.*]]
; CHECK-NEXT: ret float [[R]] ; CHECK-NEXT: ret float [[R]]
; ;
%neg = fsub float -0.000000e+00, %x %neg = fsub float -0.000000e+00, %x
@ -533,8 +533,8 @@ define float @fsub_fdiv_fneg2_extra_use2(float %x, float %y, float %z) {
; CHECK-LABEL: @fsub_fdiv_fneg2_extra_use2( ; CHECK-LABEL: @fsub_fdiv_fneg2_extra_use2(
; CHECK-NEXT: [[NEG:%.*]] = fsub float -0.000000e+00, [[X:%.*]] ; CHECK-NEXT: [[NEG:%.*]] = fsub float -0.000000e+00, [[X:%.*]]
; CHECK-NEXT: call void @use(float [[NEG]]) ; CHECK-NEXT: call void @use(float [[NEG]])
; CHECK-NEXT: [[DIV:%.*]] = fdiv float [[Y:%.*]], [[NEG]] ; CHECK-NEXT: [[TMP1:%.*]] = fdiv float [[Y:%.*]], [[X]]
; CHECK-NEXT: [[R:%.*]] = fsub float [[Z:%.*]], [[DIV]] ; CHECK-NEXT: [[R:%.*]] = fadd float [[TMP1]], [[Z:%.*]]
; CHECK-NEXT: ret float [[R]] ; CHECK-NEXT: ret float [[R]]
; ;
%neg = fsub float -0.000000e+00, %x %neg = fsub float -0.000000e+00, %x
@ -548,8 +548,8 @@ define <2 x float> @fsub_fmul_fneg1_extra_use2(<2 x float> %x, <2 x float> %y, <
; CHECK-LABEL: @fsub_fmul_fneg1_extra_use2( ; CHECK-LABEL: @fsub_fmul_fneg1_extra_use2(
; CHECK-NEXT: [[NEG:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[X:%.*]] ; CHECK-NEXT: [[NEG:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[X:%.*]]
; CHECK-NEXT: call void @use_vec(<2 x float> [[NEG]]) ; CHECK-NEXT: call void @use_vec(<2 x float> [[NEG]])
; CHECK-NEXT: [[MUL:%.*]] = fmul <2 x float> [[NEG]], [[Y:%.*]] ; CHECK-NEXT: [[TMP1:%.*]] = fmul <2 x float> [[X]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = fsub <2 x float> [[Z:%.*]], [[MUL]] ; CHECK-NEXT: [[R:%.*]] = fadd <2 x float> [[TMP1]], [[Z:%.*]]
; CHECK-NEXT: ret <2 x float> [[R]] ; CHECK-NEXT: ret <2 x float> [[R]]
; ;
%neg = fsub <2 x float> <float -0.0, float -0.0>, %x %neg = fsub <2 x float> <float -0.0, float -0.0>, %x
@ -563,8 +563,8 @@ define float @fsub_fmul_fneg2_extra_use2(float %x, float %y, float %z) {
; CHECK-LABEL: @fsub_fmul_fneg2_extra_use2( ; CHECK-LABEL: @fsub_fmul_fneg2_extra_use2(
; CHECK-NEXT: [[NEG:%.*]] = fsub float -0.000000e+00, [[X:%.*]] ; CHECK-NEXT: [[NEG:%.*]] = fsub float -0.000000e+00, [[X:%.*]]
; CHECK-NEXT: call void @use(float [[NEG]]) ; CHECK-NEXT: call void @use(float [[NEG]])
; CHECK-NEXT: [[MUL:%.*]] = fmul float [[NEG]], [[Y:%.*]] ; CHECK-NEXT: [[TMP1:%.*]] = fmul float [[X]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = fsub float [[Z:%.*]], [[MUL]] ; CHECK-NEXT: [[R:%.*]] = fadd float [[TMP1]], [[Z:%.*]]
; CHECK-NEXT: ret float [[R]] ; CHECK-NEXT: ret float [[R]]
; ;
%neg = fsub float -0.000000e+00, %x %neg = fsub float -0.000000e+00, %x