[llvm] r302510 - [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.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Tue May  9 02:04:04 2017
New Revision: 302510

URL: http://llvm.org/viewvc/llvm-project?rev=302510&view=rev
Log:
[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.

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=302510&r1=302509&r2=302510&view=diff
==============================================================================
--- llvm/trunk/lib/IR/ConstantRange.cpp (original)
+++ llvm/trunk/lib/IR/ConstantRange.cpp Tue May  9 02:04:04 2017
@@ -892,16 +892,20 @@ ConstantRange::shl(const ConstantRange &
   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