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[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.

llvm-svn: 302952
This commit is contained in:
Craig Topper 2017-05-12 21:45:44 +00:00
parent 1fa362f811
commit 2579c7c69f
1 changed files with 5 additions and 4 deletions
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9
llvm/lib/Support/APInt.cpp
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@ -1648,14 +1648,15 @@ APInt APInt::srem(const APInt &RHS) const {
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, const APInt &RHS,
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;