From 00b83c9b8d04eb391912320437ee5172a02ca8ce Mon Sep 17 00:00:00 2001
From: Pedro Artigas <partigas@apple.com>
Date: Fri, 30 Nov 2012 22:47:15 +0000
Subject: [PATCH] reversed the logic of the log2 detection routine to reduce
 the number of nested ifs

llvm-svn: 169049
---
 .../InstCombine/InstCombineMulDivRem.cpp           | 54 ++++++++++++----------
 1 file changed, 29 insertions(+), 25 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index b0b9bac..2fc5f85 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -261,31 +261,35 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
 //
 
 static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
-   if (Op->hasOneUse()) {
-    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op)) {
-      if (II->getIntrinsicID() == Intrinsic::log2 &&
-          II->hasUnsafeAlgebra()) {
-        Log2 = II;
-        Value *OpLog2Of = II->getArgOperand(0);
-        if (OpLog2Of->hasOneUse()) {
-          if (Instruction *I = dyn_cast<Instruction>(OpLog2Of)) {
-            if (I->getOpcode() == Instruction::FMul &&
-                I->hasUnsafeAlgebra()) {
-              ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(0));
-              if (CFP && CFP->isExactlyValue(0.5)) {
-                Y = I->getOperand(1);
-              } else {
-                CFP = dyn_cast<ConstantFP>(I->getOperand(1));
-                if (CFP && CFP->isExactlyValue(0.5)) {
-                  Y = I->getOperand(0);
-                }
-              }
-            }
-          }
-        }
-      }
-    }
-  }
+
+   if (!Op->hasOneUse())
+     return;
+
+   IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
+   if (!II)
+     return;
+   if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
+     return;
+   Log2 = II;
+
+   Value *OpLog2Of = II->getArgOperand(0);
+   if (!OpLog2Of->hasOneUse())
+     return;
+
+   Instruction *I = dyn_cast<Instruction>(OpLog2Of);
+   if (!I)
+     return;
+   if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
+     return;
+              
+   ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(0));
+   if (CFP && CFP->isExactlyValue(0.5)) {
+     Y = I->getOperand(1);
+     return;
+   }
+   CFP = dyn_cast<ConstantFP>(I->getOperand(1));
+   if (CFP && CFP->isExactlyValue(0.5))
+     Y = I->getOperand(0);
 } 
 
 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
-- 
2.7.4