RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2026-07-19 15:13:49 -04:00
Code Issues Packages Projects Releases 10 Wiki Activity

APInt: Slightly simplify countLeadingZerosSlowCase()

Browse Source 
We always clear the unused bits in the most signifant word so there is
no need to mask them out in countLeadingZerosSlowCase().

Differential Revision: http://reviews.llvm.org/D16621

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260911 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun
2016-02-15 20:06:22 +00:00
parent 17946378fd
commit 294f6d04dd
1 changed files with 8 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/Support/APInt.cpp
+8 -19
View File
@@ -676,30 +676,19 @@ APInt APInt::getLoBits(unsigned numBits) const {
}
unsigned APInt::countLeadingZerosSlowCase() const {
// Treat the most significand word differently because it might have
// meaningless bits set beyond the precision.
unsigned BitsInMSW = BitWidth % APINT_BITS_PER_WORD;
integerPart MSWMask;
if (BitsInMSW) MSWMask = (integerPart(1) << BitsInMSW) - 1;
else {
MSWMask = ~integerPart(0);
BitsInMSW = APINT_BITS_PER_WORD;
}
unsigned i = getNumWords();
integerPart MSW = pVal[i-1] & MSWMask;
if (MSW)
return llvm::countLeadingZeros(MSW) - (APINT_BITS_PER_WORD - BitsInMSW);
unsigned Count = BitsInMSW;
for (--i; i > 0u; --i) {
if (pVal[i-1] == 0)
unsigned Count = 0;
for (int i = getNumWords()-1; i >= 0; --i) {
integerPart V = pVal[i];
if (V == 0)
Count += APINT_BITS_PER_WORD;
else {
Count += llvm::countLeadingZeros(pVal[i-1]);
Count += llvm::countLeadingZeros(V);
break;
}
}
// Adjust for unused bits in the most significant word (they are zero).
unsigned Mod = BitWidth % APINT_BITS_PER_WORD;
Count -= Mod > 0 ? APINT_BITS_PER_WORD - Mod : 0;
return Count;
}