[InstCombine] Added llvm.powi optimizations

If power is even: powi(-x, p) -> powi(x, p) powi(fabs(x), p) -> powi(x, p) powi(copysign(x, y), p) -> powi(x, p)
llvm · Sep 16, 2021 · a4a426c · a4a426c
1 parent c0afb00
commit a4a426c
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Showing 2 changed files with 16 additions and 6 deletions.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1182,6 +1182,19 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
       if (Power->equalsInt(2))
         return BinaryOperator::CreateFMulFMF(II->getArgOperand(0),
                                              II->getArgOperand(0), II);
+
+      if (!Power->getValue()[0]) {
+        Value *X;
+        // If power is even:
+        // powi(-x, p) -> powi(x, p)
+        // powi(fabs(x), p) -> powi(x, p)
+        // powi(copysign(x, y), p) -> powi(x, p)
+        if (match(II->getArgOperand(0), m_FNeg(m_Value(X))) ||
+            match(II->getArgOperand(0), m_FAbs(m_Value(X))) ||
+            match(II->getArgOperand(0),
+                  m_Intrinsic<Intrinsic::copysign>(m_Value(X), m_Value())))
+          return replaceOperand(*II, 0, X);
+      }
     }
     break;
 

diff --git a/llvm/test/Transforms/InstCombine/powi.ll b/llvm/test/Transforms/InstCombine/powi.ll
@@ -8,8 +8,7 @@ declare double @llvm.copysign.f64(double, double)
 define double @powi_fneg_even_int(double %x) {
 ; CHECK-LABEL: @powi_fneg_even_int(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[FNEG:%.*]] = fneg double [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = tail call double @llvm.powi.f64.i32(double [[FNEG]], i32 4)
+; CHECK-NEXT:    [[R:%.*]] = tail call double @llvm.powi.f64.i32(double [[X:%.*]], i32 4)
 ; CHECK-NEXT:    ret double [[R]]
 ;
 entry:
@@ -21,8 +20,7 @@ entry:
 define double @powi_fabs_even_int(double %x) {
 ; CHECK-LABEL: @powi_fabs_even_int(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[F:%.*]] = tail call double @llvm.fabs.f64(double [[X:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = tail call double @llvm.powi.f64.i32(double [[F]], i32 4)
+; CHECK-NEXT:    [[R:%.*]] = tail call double @llvm.powi.f64.i32(double [[X:%.*]], i32 4)
 ; CHECK-NEXT:    ret double [[R]]
 ;
 entry:
@@ -34,8 +32,7 @@ entry:
 define double @powi_copysign_even_int(double %x, double %y) {
 ; CHECK-LABEL: @powi_copysign_even_int(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[CS:%.*]] = tail call double @llvm.copysign.f64(double [[X:%.*]], double [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = tail call double @llvm.powi.f64.i32(double [[CS]], i32 4)
+; CHECK-NEXT:    [[R:%.*]] = tail call double @llvm.powi.f64.i32(double [[X:%.*]], i32 4)
 ; CHECK-NEXT:    ret double [[R]]
 ;
 entry: