[llvm] r290715 - [ADT] Use memcpy for type punning in MathExtras.
Justin Lebar via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 29 10:15:34 PST 2016
Author: jlebar
Date: Thu Dec 29 12:15:34 2016
New Revision: 290715
URL: http://llvm.org/viewvc/llvm-project?rev=290715&view=rev
Log:
[ADT] Use memcpy for type punning in MathExtras.
Summary: Previously we type-punned through a union, which is not safe.
Reviewers: rnk
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D28161
Modified:
llvm/trunk/include/llvm/Support/MathExtras.h
Modified: llvm/trunk/include/llvm/Support/MathExtras.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MathExtras.h?rev=290715&r1=290714&r2=290715&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/MathExtras.h (original)
+++ llvm/trunk/include/llvm/Support/MathExtras.h Thu Dec 29 12:15:34 2016
@@ -547,23 +547,19 @@ inline uint64_t GreatestCommonDivisor64(
/// BitsToDouble - This function takes a 64-bit integer and returns the bit
/// equivalent double.
inline double BitsToDouble(uint64_t Bits) {
- union {
- uint64_t L;
- double D;
- } T;
- T.L = Bits;
- return T.D;
+ double D;
+ static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
+ memcpy(&D, &Bits, sizeof(Bits));
+ return D;
}
/// BitsToFloat - This function takes a 32-bit integer and returns the bit
/// equivalent float.
inline float BitsToFloat(uint32_t Bits) {
- union {
- uint32_t I;
- float F;
- } T;
- T.I = Bits;
- return T.F;
+ float F;
+ static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
+ memcpy(&F, &Bits, sizeof(Bits));
+ return F;
}
/// DoubleToBits - This function takes a double and returns the bit
@@ -571,12 +567,10 @@ inline float BitsToFloat(uint32_t Bits)
/// changes the bits of NaNs on some hosts, notably x86, so this
/// routine cannot be used if these bits are needed.
inline uint64_t DoubleToBits(double Double) {
- union {
- uint64_t L;
- double D;
- } T;
- T.D = Double;
- return T.L;
+ uint64_t Bits;
+ static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
+ memcpy(&Bits, &Double, sizeof(Double));
+ return Bits;
}
/// FloatToBits - This function takes a float and returns the bit
@@ -584,12 +578,10 @@ inline uint64_t DoubleToBits(double Doub
/// changes the bits of NaNs on some hosts, notably x86, so this
/// routine cannot be used if these bits are needed.
inline uint32_t FloatToBits(float Float) {
- union {
- uint32_t I;
- float F;
- } T;
- T.F = Float;
- return T.I;
+ uint32_t Bits;
+ static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
+ memcpy(&Bits, &Float, sizeof(Float));
+ return Bits;
}
/// MinAlign - A and B are either alignments or offsets. Return the minimum
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