From: Craig Topper <craig.topper@gmail.com>
Date: Tue, 9 May 2017 07:04:04 +0000 (+0000)
Subject: [ConstantRange] Rewrite shl to avoid repeated calls to getUnsignedMax and avoid creat... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b23f8ea900dc493c596616bc449c8ee9bc20310e;p=llvm

[ConstantRange] Rewrite shl to avoid repeated calls to getUnsignedMax and avoid creating the min APInt until we're sure we need it. Use inplace shift operations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302510 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/IR/ConstantRange.cpp b/lib/IR/ConstantRange.cpp
index 6801ed4fb51..a33d062dbea 100644
--- a/lib/IR/ConstantRange.cpp
+++ b/lib/IR/ConstantRange.cpp
@@ -892,16 +892,20 @@ ConstantRange::shl(const ConstantRange &Other) const {
   if (isEmptySet() || Other.isEmptySet())
     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 
-  APInt min = getUnsignedMin().shl(Other.getUnsignedMin());
-  APInt max = getUnsignedMax().shl(Other.getUnsignedMax());
+  APInt max = getUnsignedMax();
+  APInt Other_umax = Other.getUnsignedMax();
 
-  // there's no overflow!
-  APInt Zeros(getBitWidth(), getUnsignedMax().countLeadingZeros());
-  if (Zeros.ugt(Other.getUnsignedMax()))
-    return ConstantRange(std::move(min), std::move(max) + 1);
+  // there's overflow!
+  if (Other_umax.uge(max.countLeadingZeros()))
+    return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 
   // FIXME: implement the other tricky cases
-  return ConstantRange(getBitWidth(), /*isFullSet=*/true);
+
+  APInt min = getUnsignedMin();
+  min <<= Other.getUnsignedMin();
+  max <<= Other_umax;
+
+  return ConstantRange(std::move(min), std::move(max) + 1);
 }
 
 ConstantRange