[llvm] r300621 - [ConstantRange] Optimize APInt creation in getSignedMax/getSignedMin.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Tue Apr 18 18:02:39 2017
New Revision: 300621

URL: http://llvm.org/viewvc/llvm-project?rev=300621&view=rev
Log:
[ConstantRange] Optimize APInt creation in getSignedMax/getSignedMin.

We were creating an APInt at the top of these methods that isn't always returned. For ranges wider than 64-bits this results in an allocation and deallocation when its not used.

In getSignedMax we were creating Upper-1 to use in a compare and then creating it again for a return value. The compiler is unable to determine that these can be shared. So help it out and create the Upper-1 in a temporary that can be reused.

This provides a little compile time improvement.


Modified:
    llvm/trunk/lib/IR/ConstantRange.cpp

Modified: llvm/trunk/lib/IR/ConstantRange.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/ConstantRange.cpp?rev=300621&r1=300620&r2=300621&view=diff
==============================================================================
--- llvm/trunk/lib/IR/ConstantRange.cpp (original)
+++ llvm/trunk/lib/IR/ConstantRange.cpp Tue Apr 18 18:02:39 2017
@@ -281,25 +281,25 @@ APInt ConstantRange::getUnsignedMin() co
 APInt ConstantRange::getSignedMax() const {
   APInt SignedMax(APInt::getSignedMaxValue(getBitWidth()));
   if (!isWrappedSet()) {
-    if (getLower().sle(getUpper() - 1))
-      return getUpper() - 1;
-    return SignedMax;
+    APInt UpperMinusOne = getUpper() - 1;
+    if (getLower().sle(UpperMinusOne))
+      return UpperMinusOne;
+    return APInt::getSignedMaxValue(getBitWidth());
   }
   if (getLower().isNegative() == getUpper().isNegative())
-    return SignedMax;
+    return APInt::getSignedMaxValue(getBitWidth());
   return getUpper() - 1;
 }
 
 APInt ConstantRange::getSignedMin() const {
-  APInt SignedMin(APInt::getSignedMinValue(getBitWidth()));
   if (!isWrappedSet()) {
     if (getLower().sle(getUpper() - 1))
       return getLower();
-    return SignedMin;
+    return APInt::getSignedMinValue(getBitWidth());
   }
   if ((getUpper() - 1).slt(getLower())) {
-    if (getUpper() != SignedMin)
-      return SignedMin;
+    if (!getUpper().isMinSignedValue())
+      return APInt::getSignedMinValue(getBitWidth());
   }
   return getLower();
 }