[llvm] 0985202 - [InstCombine] optimize powi(X,Y) * X with Ofast
via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 14 07:06:43 PDT 2024
Author: zhongyunde 00443407
Date: 2024-03-14T22:05:20+08:00
New Revision: 098520244f90e9330d3ae78bd1061aee2e3688c0
URL: https://github.com/llvm/llvm-project/commit/098520244f90e9330d3ae78bd1061aee2e3688c0
DIFF: https://github.com/llvm/llvm-project/commit/098520244f90e9330d3ae78bd1061aee2e3688c0.diff
LOG: [InstCombine] optimize powi(X,Y) * X with Ofast
Try to transform the powi(X, Y) * X into powi(X, Y+1) with Ofast
For this case, when the Y is 3, then powi(X, 4) is replaced by
X2 = X * X; X2 * X2 in the further step.
Similar to D109954, who requires reassoc.
Fixes https://github.com/llvm/llvm-project/issues/69862.
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
llvm/test/Transforms/InstCombine/powi.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 278be6233f4b8a..55d89c6108f033 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -683,6 +683,18 @@ Instruction *InstCombinerImpl::foldFMulReassoc(BinaryOperator &I) {
return replaceInstUsesWith(I, Pow);
}
+ // powi(X, Y) * X --> powi(X, Y+1)
+ // X * powi(X, Y) --> powi(X, Y+1)
+ if (match(&I, m_c_FMul(m_OneUse(m_Intrinsic<Intrinsic::powi>(m_Value(X),
+ m_Value(Y))),
+ m_Deferred(X))) &&
+ willNotOverflowSignedAdd(Y, ConstantInt::get(Y->getType(), 1), I)) {
+ auto *Y1 = Builder.CreateAdd(Y, ConstantInt::get(Y->getType(), 1));
+ auto *NewPow = Builder.CreateIntrinsic(
+ Intrinsic::powi, {X->getType(), Y1->getType()}, {X, Y1}, &I);
+ return replaceInstUsesWith(I, NewPow);
+ }
+
if (I.isOnlyUserOfAnyOperand()) {
// pow(X, Y) * pow(X, Z) -> pow(X, Y + Z)
if (match(Op0, m_Intrinsic<Intrinsic::pow>(m_Value(X), m_Value(Y))) &&
diff --git a/llvm/test/Transforms/InstCombine/powi.ll b/llvm/test/Transforms/InstCombine/powi.ll
index 89efbb6f453611..95722d09a17ad3 100644
--- a/llvm/test/Transforms/InstCombine/powi.ll
+++ b/llvm/test/Transforms/InstCombine/powi.ll
@@ -341,3 +341,52 @@ define double @fdiv_pow_powi_negative_variable(double %x, i32 %y) {
%div = fdiv reassoc nnan double %p1, %x
ret double %div
}
+
+; powi(X, Y) * X --> powi(X, Y+1)
+define double @powi_fmul_powi_x(double noundef %x) {
+; CHECK-LABEL: @powi_fmul_powi_x(
+; CHECK-NEXT: [[MUL:%.*]] = call reassoc double @llvm.powi.f64.i32(double [[X:%.*]], i32 4)
+; CHECK-NEXT: ret double [[MUL]]
+;
+ %p1 = tail call double @llvm.powi.f64.i32(double %x, i32 3)
+ %mul = fmul reassoc double %p1, %x
+ ret double %mul
+}
+
+; Negative test: Multi-use
+define double @powi_fmul_powi_x_multi_use(double noundef %x) {
+; CHECK-LABEL: @powi_fmul_powi_x_multi_use(
+; CHECK-NEXT: [[P1:%.*]] = tail call double @llvm.powi.f64.i32(double [[X:%.*]], i32 3)
+; CHECK-NEXT: tail call void @use(double [[P1]])
+; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[P1]], [[X]]
+; CHECK-NEXT: ret double [[MUL]]
+;
+ %p1 = tail call double @llvm.powi.f64.i32(double %x, i32 3)
+ tail call void @use(double %p1)
+ %mul = fmul reassoc double %p1, %x
+ ret double %mul
+}
+
+; Negative test: Miss fmf flag
+define double @powi_fmul_powi_x_missing_reassoc(double noundef %x) {
+; CHECK-LABEL: @powi_fmul_powi_x_missing_reassoc(
+; CHECK-NEXT: [[P1:%.*]] = tail call double @llvm.powi.f64.i32(double [[X:%.*]], i32 3)
+; CHECK-NEXT: [[MUL:%.*]] = fmul double [[P1]], [[X]]
+; CHECK-NEXT: ret double [[MUL]]
+;
+ %p1 = tail call double @llvm.powi.f64.i32(double %x, i32 3)
+ %mul = fmul double %p1, %x
+ ret double %mul
+}
+
+; Negative test: overflow
+define double @powi_fmul_powi_x_overflow(double noundef %x) {
+; CHECK-LABEL: @powi_fmul_powi_x_overflow(
+; CHECK-NEXT: [[P1:%.*]] = tail call double @llvm.powi.f64.i32(double [[X:%.*]], i32 2147483647)
+; CHECK-NEXT: [[MUL:%.*]] = fmul reassoc double [[P1]], [[X]]
+; CHECK-NEXT: ret double [[MUL]]
+;
+ %p1 = tail call double @llvm.powi.f64.i32(double %x, i32 2147483647) ; INT_MAX
+ %mul = fmul reassoc double %p1, %x
+ ret double %mul
+}
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