From 85bd15a2b115caac021fd222ba2d3d910142289a Mon Sep 17 00:00:00 2001
From: Philip Reames <listmail@philipreames.com>
Date: Wed, 27 Dec 2017 01:30:12 +0000
Subject: [PATCH] [instcombine] add powi(x, 2) -> x * x

llvm-svn: 321468
---
 lib/Transforms/InstCombine/InstCombineCalls.cpp | 4 ++++
 test/Transforms/InstCombine/intrinsics.ll       | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 4dfb22abb6e..5e0778d9ae2 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1934,6 +1934,10 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
       if (Power->isMinusOne())
         return BinaryOperator::CreateFDiv(ConstantFP::get(CI.getType(), 1.0),
                                           II->getArgOperand(0));
+      // powi(x, 2) -> x*x
+      if (Power->equalsInt(2))
+        return BinaryOperator::CreateFMul(II->getArgOperand(0),
+                                          II->getArgOperand(0));
     }
     break;
 
diff --git a/test/Transforms/InstCombine/intrinsics.ll b/test/Transforms/InstCombine/intrinsics.ll
index c6f88fb9cf0..e0698f8b3b7 100644
--- a/test/Transforms/InstCombine/intrinsics.ll
+++ b/test/Transforms/InstCombine/intrinsics.ll
@@ -267,12 +267,17 @@ define void @powi(double %V, double *%P) {
 
   %C = tail call double @llvm.powi.f64(double %V, i32 1) nounwind
   store volatile double %C, double* %P
+
+  %D = tail call double @llvm.powi.f64(double %V, i32 2) nounwind
+  store volatile double %D, double* %P
   ret void
 ; CHECK-LABEL: @powi(
 ; CHECK: %A = fdiv double 1.0{{.*}}, %V
 ; CHECK: store volatile double %A,
 ; CHECK: store volatile double 1.0
 ; CHECK: store volatile double %V
+; CHECK: %D = fmul double %V, %V
+; CHECK: store volatile double %D
 }
 
 define i32 @cttz(i32 %a) {