[llvm] r302952 - [APInt] In udivrem, remember the bit width in a local variable so we don't reread it from the LHS which might be aliased with Quotient or Remainder.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Fri May 12 16:45:44 2017
New Revision: 302952

URL: http://llvm.org/viewvc/llvm-project?rev=302952&view=rev
Log:
[APInt] In udivrem, remember the bit width in a local variable so we don't reread it from the LHS which might be aliased with Quotient or Remainder.

This helped the compiler generate better code for the single word case. It was able to remember that the bit width was still a single word when it created the Remainder APInt and not create code for it possibly being multiword.

Modified:
    llvm/trunk/lib/Support/APInt.cpp

Modified: llvm/trunk/lib/Support/APInt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APInt.cpp?rev=302952&r1=302951&r2=302952&view=diff
==============================================================================
--- llvm/trunk/lib/Support/APInt.cpp (original)
+++ llvm/trunk/lib/Support/APInt.cpp Fri May 12 16:45:44 2017
@@ -1648,14 +1648,15 @@ APInt APInt::srem(const APInt &RHS) cons
 void APInt::udivrem(const APInt &LHS, const APInt &RHS,
                     APInt &Quotient, APInt &Remainder) {
   assert(LHS.BitWidth == RHS.BitWidth && "Bit widths must be the same");
+  unsigned BitWidth = LHS.BitWidth;
 
   // First, deal with the easy case
   if (LHS.isSingleWord()) {
     assert(RHS.U.VAL != 0 && "Divide by zero?");
     uint64_t QuotVal = LHS.U.VAL / RHS.U.VAL;
     uint64_t RemVal = LHS.U.VAL % RHS.U.VAL;
-    Quotient = APInt(LHS.BitWidth, QuotVal);
-    Remainder = APInt(LHS.BitWidth, RemVal);
+    Quotient = APInt(BitWidth, QuotVal);
+    Remainder = APInt(BitWidth, RemVal);
     return;
   }
 
@@ -1688,8 +1689,8 @@ void APInt::udivrem(const APInt &LHS, co
     uint64_t lhsValue = LHS.U.pVal[0];
     uint64_t rhsValue = RHS.U.pVal[0];
     // Make sure there is enough space to hold the results.
-    Quotient.reallocate(LHS.BitWidth);
-    Remainder.reallocate(LHS.BitWidth);
+    Quotient.reallocate(BitWidth);
+    Remainder.reallocate(BitWidth);
     Quotient = lhsValue / rhsValue;
     Remainder = lhsValue % rhsValue;
     return;