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[InstCombine] Missed optimization in math expression: simplify calls …
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…exp functions

Summary: This patch enables folding following expressions under -ffast-math flag: exp(X) * exp(Y) -> exp(X + Y), exp2(X) * exp2(Y) -> exp2(X + Y). Motivation: https://bugs.llvm.org/show_bug.cgi?id=35594

Reviewers: hfinkel, spatel, efriedma, lebedev.ri

Reviewed By: spatel, lebedev.ri

Subscribers: lebedev.ri, llvm-commits

Differential Revision: https://reviews.llvm.org/D41342

llvm-svn: 352730
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@Quolyk
Quolyk committed Jan 31, 2019
1 parent 0e712a7 commit 8817658
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Showing 3 changed files with 42 additions and 30 deletions.
20 changes: 20 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View file
Expand Up @@ -441,6 +441,26 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
return replaceInstUsesWith(I, Sqrt);
}

// exp(X) * exp(Y) -> exp(X + Y)
// Match as long as at least one of exp has only one use.
if (match(Op0, m_Intrinsic<Intrinsic::exp>(m_Value(X))) &&
match(Op1, m_Intrinsic<Intrinsic::exp>(m_Value(Y))) &&
(Op0->hasOneUse() || Op1->hasOneUse())) {
Value *XY = Builder.CreateFAddFMF(X, Y, &I);
Value *Exp = Builder.CreateUnaryIntrinsic(Intrinsic::exp, XY, &I);
return replaceInstUsesWith(I, Exp);
}

// exp2(X) * exp2(Y) -> exp2(X + Y)
// Match as long as at least one of exp2 has only one use.
if (match(Op0, m_Intrinsic<Intrinsic::exp2>(m_Value(X))) &&
match(Op1, m_Intrinsic<Intrinsic::exp2>(m_Value(Y))) &&
(Op0->hasOneUse() || Op1->hasOneUse())) {
Value *XY = Builder.CreateFAddFMF(X, Y, &I);
Value *Exp2 = Builder.CreateUnaryIntrinsic(Intrinsic::exp2, XY, &I);
return replaceInstUsesWith(I, Exp2);
}

// (X*Y) * X => (X*X) * Y where Y != X
// The purpose is two-fold:
// 1) to form a power expression (of X).
Expand Down
26 changes: 11 additions & 15 deletions llvm/test/Transforms/InstCombine/fmul-exp.ll
View file
Expand Up @@ -21,11 +21,11 @@ define double @exp_a_exp_b(double %a, double %b) {
; exp(a) * exp(b) reassoc, multiple uses
define double @exp_a_exp_b_multiple_uses(double %a, double %b) {
; CHECK-LABEL: @exp_a_exp_b_multiple_uses(
; CHECK-NEXT: [[TMP:%.*]] = call double @llvm.exp.f64(double [[A:%.*]])
; CHECK-NEXT: [[TMP1:%.*]] = call double @llvm.exp.f64(double [[B:%.*]])
; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[TMP]], [[TMP1]]
; CHECK-NEXT: [[TMP:%.*]] = fadd reassoc double [[A:%.*]], [[B]]
; CHECK-NEXT: [[TMP2:%.*]] = call reassoc double @llvm.exp.f64(double [[TMP]])
; CHECK-NEXT: call void @use(double [[TMP1]])
; CHECK-NEXT: ret double [[MUL]]
; CHECK-NEXT: ret double [[TMP2]]
;
%tmp = call double @llvm.exp.f64(double %a)
%tmp1 = call double @llvm.exp.f64(double %b)
Expand Down Expand Up @@ -55,10 +55,9 @@ define double @exp_a_exp_b_multiple_uses_both(double %a, double %b) {
; exp(a) * exp(b) => exp(a+b) with reassoc
define double @exp_a_exp_b_reassoc(double %a, double %b) {
; CHECK-LABEL: @exp_a_exp_b_reassoc(
; CHECK-NEXT: [[TMP:%.*]] = call double @llvm.exp.f64(double [[A:%.*]])
; CHECK-NEXT: [[TMP1:%.*]] = call double @llvm.exp.f64(double [[B:%.*]])
; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[TMP]], [[TMP1]]
; CHECK-NEXT: ret double [[MUL]]
; CHECK-NEXT: [[TMP:%.*]] = fadd reassoc double [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = call reassoc double @llvm.exp.f64(double [[TMP]])
; CHECK-NEXT: ret double [[TMP1]]
;
%tmp = call double @llvm.exp.f64(double %a)
%tmp1 = call double @llvm.exp.f64(double %b)
Expand All @@ -69,14 +68,11 @@ define double @exp_a_exp_b_reassoc(double %a, double %b) {
; exp(a) * exp(b) * exp(c) * exp(d) => exp(a+b+c+d) with reassoc
define double @exp_a_exp_b_exp_c_exp_d_fast(double %a, double %b, double %c, double %d) {
; CHECK-LABEL: @exp_a_exp_b_exp_c_exp_d_fast(
; CHECK-NEXT: [[TMP:%.*]] = call double @llvm.exp.f64(double [[A:%.*]])
; CHECK-NEXT: [[TMP1:%.*]] = call double @llvm.exp.f64(double [[B:%.*]])
; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[TMP]], [[TMP1]]
; CHECK-NEXT: [[TMP2:%.*]] = call double @llvm.exp.f64(double [[C:%.*]])
; CHECK-NEXT: [[MUL1:%.*]] = fmul reassoc double [[MUL]], [[TMP2]]
; CHECK-NEXT: [[TMP3:%.*]] = call double @llvm.exp.f64(double [[D:%.*]])
; CHECK-NEXT: [[MUL2:%.*]] = fmul reassoc double [[MUL1]], [[TMP3]]
; CHECK-NEXT: ret double [[MUL2]]
; CHECK-NEXT: [[TMP:%.*]] = fadd reassoc double [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = fadd reassoc double [[TMP]], [[C:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fadd reassoc double [[TMP1]], [[D:%.*]]
; CHECK-NEXT: [[TMP3:%.*]] = call reassoc double @llvm.exp.f64(double [[TMP2]])
; CHECK-NEXT: ret double [[TMP3]]
;
%tmp = call double @llvm.exp.f64(double %a)
%tmp1 = call double @llvm.exp.f64(double %b)
Expand Down
26 changes: 11 additions & 15 deletions llvm/test/Transforms/InstCombine/fmul-exp2.ll
View file
Expand Up @@ -21,11 +21,11 @@ define double @exp2_a_exp2_b(double %a, double %b) {
; exp2(a) * exp2(b) reassoc, multiple uses
define double @exp2_a_exp2_b_multiple_uses(double %a, double %b) {
; CHECK-LABEL: @exp2_a_exp2_b_multiple_uses(
; CHECK-NEXT: [[TMP:%.*]] = call double @llvm.exp2.f64(double [[A:%.*]])
; CHECK-NEXT: [[TMP1:%.*]] = call double @llvm.exp2.f64(double [[B:%.*]])
; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[TMP]], [[TMP1]]
; CHECK-NEXT: [[TMP:%.*]] = fadd reassoc double [[A:%.*]], [[B]]
; CHECK-NEXT: [[TMP2:%.*]] = call reassoc double @llvm.exp2.f64(double [[TMP]])
; CHECK-NEXT: call void @use(double [[TMP1]])
; CHECK-NEXT: ret double [[MUL]]
; CHECK-NEXT: ret double [[TMP2]]
;
%tmp = call double @llvm.exp2.f64(double %a)
%tmp1 = call double @llvm.exp2.f64(double %b)
Expand Down Expand Up @@ -55,10 +55,9 @@ define double @exp2_a_exp2_b_multiple_uses_both(double %a, double %b) {
; exp2(a) * exp2(b) => exp2(a+b) with reassoc
define double @exp2_a_exp2_b_reassoc(double %a, double %b) {
; CHECK-LABEL: @exp2_a_exp2_b_reassoc(
; CHECK-NEXT: [[TMP:%.*]] = call double @llvm.exp2.f64(double [[A:%.*]])
; CHECK-NEXT: [[TMP1:%.*]] = call double @llvm.exp2.f64(double [[B:%.*]])
; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[TMP]], [[TMP1]]
; CHECK-NEXT: ret double [[MUL]]
; CHECK-NEXT: [[TMP:%.*]] = fadd reassoc double [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = call reassoc double @llvm.exp2.f64(double [[TMP]])
; CHECK-NEXT: ret double [[TMP1]]
;
%tmp = call double @llvm.exp2.f64(double %a)
%tmp1 = call double @llvm.exp2.f64(double %b)
Expand All @@ -69,14 +68,11 @@ define double @exp2_a_exp2_b_reassoc(double %a, double %b) {
; exp2(a) * exp2(b) * exp2(c) * exp2(d) => exp2(a+b+c+d) with reassoc
define double @exp2_a_exp2_b_exp2_c_exp2_d(double %a, double %b, double %c, double %d) {
; CHECK-LABEL: @exp2_a_exp2_b_exp2_c_exp2_d(
; CHECK-NEXT: [[TMP:%.*]] = call double @llvm.exp2.f64(double [[A:%.*]])
; CHECK-NEXT: [[TMP1:%.*]] = call double @llvm.exp2.f64(double [[B:%.*]])
; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[TMP]], [[TMP1]]
; CHECK-NEXT: [[TMP2:%.*]] = call double @llvm.exp2.f64(double [[C:%.*]])
; CHECK-NEXT: [[MUL1:%.*]] = fmul reassoc double [[MUL]], [[TMP2]]
; CHECK-NEXT: [[TMP3:%.*]] = call double @llvm.exp2.f64(double [[D:%.*]])
; CHECK-NEXT: [[MUL2:%.*]] = fmul reassoc double [[MUL1]], [[TMP3]]
; CHECK-NEXT: ret double [[MUL2]]
; CHECK-NEXT: [[TMP:%.*]] = fadd reassoc double [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = fadd reassoc double [[TMP]], [[C:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = fadd reassoc double [[TMP1]], [[D:%.*]]
; CHECK-NEXT: [[TMP3:%.*]] = call reassoc double @llvm.exp2.f64(double [[TMP2]])
; CHECK-NEXT: ret double [[TMP3]]
;
%tmp = call double @llvm.exp2.f64(double %a)
%tmp1 = call double @llvm.exp2.f64(double %b)
Expand Down

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