From: Craig Topper <craig.topper@gmail.com>
Date: Tue, 18 Apr 2017 23:02:39 +0000 (+0000)
Subject: [ConstantRange] Optimize APInt creation in getSignedMax/getSignedMin.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=19d17b65bdb162384a1ba486c9091d042ee99724;p=llvm

[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.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300621 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/IR/ConstantRange.cpp b/lib/IR/ConstantRange.cpp
index c1c83cca95d..0cc38b02520 100644
--- a/lib/IR/ConstantRange.cpp
+++ b/lib/IR/ConstantRange.cpp
@@ -281,25 +281,25 @@ APInt ConstantRange::getUnsignedMin() const {
 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();
 }