Changes in directory llvm/lib/Support:
APInt.cpp updated: 1.55 -> 1.56
---
Log message:
Implement countLeadingOnes() and getMinSignedBits(). This helps to minimize
the bit width of negative numbers by computing the minimum bit width for a
negative value. E.g. 0x1800000000000000 could be just 0x8000000000000000
---
Diffs of the changes: (+34 -1)
APInt.cpp | 35 ++++++++++++++++++++++++++++++++++-
1 files changed, 34 insertions(+), 1 deletion(-)
Index: llvm/lib/Support/APInt.cpp
diff -u llvm/lib/Support/APInt.cpp:1.55 llvm/lib/Support/APInt.cpp:1.56
--- llvm/lib/Support/APInt.cpp:1.55 Tue Feb 27 14:24:31 2007
+++ llvm/lib/Support/APInt.cpp Tue Feb 27 15:59:26 2007
@@ -702,6 +702,38 @@
return Count;
}
+static uint32_t countLeadingOnes_64(uint64_t V, uint32_t skip) {
+ uint32_t Count = 0;
+ if (skip)
+ V <<= skip;
+ while (V && (V & (1ULL << 63))) {
+ Count++;
+ V <<= 1;
+ }
+ return Count;
+}
+
+uint32_t APInt::countLeadingOnes() const {
+ if (isSingleWord())
+ return countLeadingOnes_64(VAL, APINT_BITS_PER_WORD - BitWidth);
+
+ uint32_t highWordBits = BitWidth % APINT_BITS_PER_WORD;
+ uint32_t shift = (highWordBits == 0 ? 0 : APINT_BITS_PER_WORD -
highWordBits);
+ int i = getNumWords() - 1;
+ uint32_t Count = countLeadingOnes_64(pVal[i], shift);
+ if (Count == highWordBits) {
+ for (i--; i >= 0; --i) {
+ if (pVal[i] == -1ULL)
+ Count += APINT_BITS_PER_WORD;
+ else {
+ Count += countLeadingOnes_64(pVal[i], 0);
+ break;
+ }
+ }
+ }
+ return Count;
+}
+
uint32_t APInt::countTrailingZeros() const {
if (isSingleWord())
return CountTrailingZeros_64(VAL);
@@ -1701,6 +1733,7 @@
else for (unsigned i = getNumWords(); i > 0; i--) {
cerr << pVal[i-1] << " ";
}
- cerr << " (" << this->toString(10) << ")\n" << std::setbase(10);
+ cerr << " U(" << this->toString(10) << ") S(" << this->toStringSigned(10)
+ << ")\n" << std::setbase(10);
}
#endif
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