From: David Majnemer <david.majnemer@gmail.com>
Date: Sun, 1 Feb 2015 19:10:19 +0000 (+0000)
Subject: ValueTracking: Make isSafeToSpeculativelyExecute a little cleaner
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=9e8b7214ede8eeec44d0a004f352ce38812074e1;p=oota-llvm.git

ValueTracking: Make isSafeToSpeculativelyExecute a little cleaner

No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227760 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index fa168a84bc0..91b64692eac 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -2620,20 +2620,20 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V,
   case Instruction::SDiv:
   case Instruction::SRem: {
     // x / y is undefined if y == 0 or x == INT_MIN and y == -1
-    const APInt *X, *Y;
-    if (match(Inst->getOperand(1), m_APInt(Y))) {
-      if (*Y != 0) {
-        if (*Y == -1) {
-          // The numerator can't be MinSignedValue if the denominator is -1.
-          if (match(Inst->getOperand(0), m_APInt(X)))
-            return !Y->isMinSignedValue();
-          // The numerator *might* be MinSignedValue.
-          return false;
-        }
-        // The denominator is not 0 or -1, it's safe to proceed.
-        return true;
-      }
-    }
+    const APInt *Numerator, *Denominator;
+    if (!match(Inst->getOperand(1), m_APInt(Denominator)))
+      return false;
+    // We cannot hoist this division if the denominator is 0.
+    if (*Denominator == 0)
+      return false;
+    // It's safe to hoist if the denominator is not 0 or -1.
+    if (*Denominator != -1)
+      return true;
+    // At this point we know that the denominator is -1.  It is safe to hoist as
+    // long we know that the numerator is not INT_MIN.
+    if (match(Inst->getOperand(0), m_APInt(Numerator)))
+      return !Numerator->isMinSignedValue();
+    // The numerator *might* be MinSignedValue.
     return false;
   }
   case Instruction::Load: {