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[InstCombine] remove flop from lerp patterns 

(Y * (1.0 - Z)) + (X * Z) -->
Y - (Y * Z) + (X * Z) -->
Y + Z * (X - Y)

This is part of solving:
https://bugs.llvm.org/show_bug.cgi?id=42716

Factoring eliminates an instruction, so that should be a good canonicalization.
The potential conversion to FMA would be handled by the backend based on target
capabilities.

Differential Revision: https://reviews.llvm.org/D65305

llvm-svn: 367101
This commit is contained in:
Sanjay Patel 2019-07-26 11:19:18 +00:00
parent d93e8ece7b
commit c229cfeb7a
2 changed files with 44 additions and 32 deletions
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20
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -1308,6 +1308,22 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
return Changed ? &I : nullptr;
}
/// Eliminate an op from a linear interpolation (lerp) pattern.
static Instruction *factorizeLerp(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
Value *X, *Y, *Z;
if (!match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_Value(Y),
m_OneUse(m_FSub(m_FPOne(),
m_Value(Z))))),
m_OneUse(m_c_FMul(m_Value(X), m_Deferred(Z))))))
return nullptr;
// (Y * (1.0 - Z)) + (X * Z) --> Y + Z * (X - Y) [8 commuted variants]
Value *XY = Builder.CreateFSubFMF(X, Y, &I);
Value *MulZ = Builder.CreateFMulFMF(Z, XY, &I);
return BinaryOperator::CreateFAddFMF(Y, MulZ, &I);
}
/// Factor a common operand out of fadd/fsub of fmul/fdiv.
static Instruction *factorizeFAddFSub(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
@ -1315,6 +1331,10 @@ static Instruction *factorizeFAddFSub(BinaryOperator &I,
I.getOpcode() == Instruction::FSub) && "Expecting fadd/fsub");
assert(I.hasAllowReassoc() && I.hasNoSignedZeros() &&
"FP factorization requires FMF");
if (Instruction *Lerp = factorizeLerp(I, Builder))
return Lerp;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Value *X, *Y, *Z;
bool IsFMul;

56
llvm/test/Transforms/InstCombine/fadd-fsub-factor.ll
View File

@ -473,10 +473,9 @@ define float @fdiv_fsub_denorm(float %x) {
define float @lerp_commute0(float %a, float %b, float %c) {
; CHECK-LABEL: @lerp_commute0(
; CHECK-NEXT: [[SUB:%.*]] = fsub fast float 1.000000e+00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul fast float [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul fast float [[C]], [[B:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast float [[MUL]], [[BC]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub fast float [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul fast float [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast float [[TMP2]], [[A]]
; CHECK-NEXT: ret float [[ADD]]
;
%sub = fsub fast float 1.0, %c
@ -488,10 +487,9 @@ define float @lerp_commute0(float %a, float %b, float %c) {
define <2 x float> @lerp_commute1(<2 x float> %a, <2 x float> %b, <2 x float> %c) {
; CHECK-LABEL: @lerp_commute1(
; CHECK-NEXT: [[SUB:%.*]] = fsub <2 x float> <float 1.000000e+00, float 1.000000e+00>, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul <2 x float> [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul <2 x float> [[C]], [[B:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast <2 x float> [[BC]], [[MUL]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub fast <2 x float> [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul fast <2 x float> [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast <2 x float> [[TMP2]], [[A]]
; CHECK-NEXT: ret <2 x float> [[ADD]]
;
%sub = fsub <2 x float> <float 1.0, float 1.0>, %c
@ -503,10 +501,9 @@ define <2 x float> @lerp_commute1(<2 x float> %a, <2 x float> %b, <2 x float> %c
define float @lerp_commute2(float %a, float %b, float %c) {
; CHECK-LABEL: @lerp_commute2(
; CHECK-NEXT: [[SUB:%.*]] = fsub float 1.000000e+00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul float [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul float [[B:%.*]], [[C]]
; CHECK-NEXT: [[ADD:%.*]] = fadd reassoc nsz float [[MUL]], [[BC]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub reassoc nsz float [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul reassoc nsz float [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd reassoc nsz float [[TMP2]], [[A]]
; CHECK-NEXT: ret float [[ADD]]
;
%sub = fsub float 1.0, %c
@ -518,10 +515,9 @@ define float @lerp_commute2(float %a, float %b, float %c) {
define float @lerp_commute3(float %a, float %b, float %c) {
; CHECK-LABEL: @lerp_commute3(
; CHECK-NEXT: [[SUB:%.*]] = fsub fast float 1.000000e+00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul float [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul float [[B:%.*]], [[C]]
; CHECK-NEXT: [[ADD:%.*]] = fadd reassoc ninf nsz float [[BC]], [[MUL]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub reassoc ninf nsz float [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul reassoc ninf nsz float [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd reassoc ninf nsz float [[TMP2]], [[A]]
; CHECK-NEXT: ret float [[ADD]]
;
%sub = fsub fast float 1.0, %c
@ -533,10 +529,9 @@ define float @lerp_commute3(float %a, float %b, float %c) {
define double @lerp_commute4(double %a, double %b, double %c) {
; CHECK-LABEL: @lerp_commute4(
; CHECK-NEXT: [[SUB:%.*]] = fsub fast double 1.000000e+00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul fast double [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul fast double [[C]], [[B:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast double [[MUL]], [[BC]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub fast double [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul fast double [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast double [[TMP2]], [[A]]
; CHECK-NEXT: ret double [[ADD]]
;
%sub = fsub fast double 1.0, %c
@ -548,10 +543,9 @@ define double @lerp_commute4(double %a, double %b, double %c) {
define double @lerp_commute5(double %a, double %b, double %c) {
; CHECK-LABEL: @lerp_commute5(
; CHECK-NEXT: [[SUB:%.*]] = fsub fast double 1.000000e+00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul fast double [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul fast double [[C]], [[B:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast double [[BC]], [[MUL]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub fast double [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul fast double [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast double [[TMP2]], [[A]]
; CHECK-NEXT: ret double [[ADD]]
;
%sub = fsub fast double 1.0, %c
@ -563,10 +557,9 @@ define double @lerp_commute5(double %a, double %b, double %c) {
define half @lerp_commute6(half %a, half %b, half %c) {
; CHECK-LABEL: @lerp_commute6(
; CHECK-NEXT: [[SUB:%.*]] = fsub fast half 0xH3C00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul fast half [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul fast half [[B:%.*]], [[C]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast half [[MUL]], [[BC]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub fast half [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul fast half [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast half [[TMP2]], [[A]]
; CHECK-NEXT: ret half [[ADD]]
;
%sub = fsub fast half 1.0, %c
@ -578,10 +571,9 @@ define half @lerp_commute6(half %a, half %b, half %c) {
define half @lerp_commute7(half %a, half %b, half %c) {
; CHECK-LABEL: @lerp_commute7(
; CHECK-NEXT: [[SUB:%.*]] = fsub fast half 0xH3C00, [[C:%.*]]
; CHECK-NEXT: [[MUL:%.*]] = fmul fast half [[SUB]], [[A:%.*]]
; CHECK-NEXT: [[BC:%.*]] = fmul fast half [[B:%.*]], [[C]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast half [[BC]], [[MUL]]
; CHECK-NEXT: [[TMP1:%.*]] = fsub fast half [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fmul fast half [[TMP1]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = fadd fast half [[TMP2]], [[A]]
; CHECK-NEXT: ret half [[ADD]]
;
%sub = fsub fast half 1.0, %c