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APInt: udivrem should use machine instructions for single-word APInts

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This mirrors the behavior of APInt::udiv and APInt::urem.  Some
architectures, like X86, have a single instruction which can compute
both division and remainder.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224217 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-12-14 09:41:56 +00:00
parent fabf5cc5d9
commit a53d2268a9
1 changed files with 12 additions and 0 deletions
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12
lib/Support/APInt.cpp
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@ -1956,6 +1956,18 @@ 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");
// First, deal with the easy case
if (LHS.isSingleWord()) {
assert(RHS.VAL != 0 && "Divide by zero?");
uint64_t QuotVal = LHS.VAL / RHS.VAL;
uint64_t RemVal = LHS.VAL % RHS.VAL;
Quotient = APInt(LHS.BitWidth, QuotVal);
Remainder = APInt(LHS.BitWidth, RemVal);
return;
}
// Get some size facts about the dividend and divisor
unsigned lhsBits = LHS.getActiveBits();
unsigned lhsWords = !lhsBits ? 0 : (APInt::whichWord(lhsBits - 1) + 1);