Changes in directory llvm/lib/Support:
APInt.cpp updated: 1.50 -> 1.51
---
Log message:
Simplify and document RoundDoubleToAPInt.
---
Diffs of the changes: (+15 -3)
APInt.cpp | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)
Index: llvm/lib/Support/APInt.cpp
diff -u llvm/lib/Support/APInt.cpp:1.50 llvm/lib/Support/APInt.cpp:1.51
--- llvm/lib/Support/APInt.cpp:1.50 Mon Feb 26 17:38:21 2007
+++ llvm/lib/Support/APInt.cpp Mon Feb 26 19:28:10 2007
@@ -803,15 +803,27 @@
uint64_t I;
} T;
T.D = Double;
+
+ // Get the sign bit from the highest order bit
bool isNeg = T.I >> 63;
+
+ // Get the 11-bit exponent and adjust for the 1023 bit bias
int64_t exp = ((T.I >> 52) & 0x7ff) - 1023;
+
+ // If the exponent is negative, the value is < 0 so just return 0.
if (exp < 0)
- return APInt(64ull, 0u);
- uint64_t mantissa = ((T.I << 12) >> 12) | (1ULL << 52);
+ return APInt(64u, 0u);
+
+ // Extract the mantissa by clearing the top 12 bits (sign + exponent).
+ uint64_t mantissa = (T.I & (~0ULL >> 12)) | 1ULL << 52;
+
+ // If the exponent doesn't shift all bits out of the mantissa
if (exp < 52)
return isNeg ? -APInt(64u, mantissa >> (52 - exp)) :
APInt(64u, mantissa >> (52 - exp));
- APInt Tmp(exp + 1, mantissa);
+
+ // Otherwise, we have to shift the mantissa bits up to the right location
+ APInt Tmp(exp+1, mantissa);
Tmp = Tmp.shl(exp - 52);
return isNeg ? -Tmp : Tmp;
}
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