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Commit c2d68045 authored by Leszek Swirski's avatar Leszek Swirski Committed by Commit Bot
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[base] Remove union type-punning UB in ieee754.cc 

Bug: v8:10122
Change-Id: I5fc28a4e567ad545ac39324240458960fc86b71c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2000744
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: 's avatarClemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65783}
parent b0ebfabc
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Showing with 37 additions and 101 deletions
src/base/ieee754.cc
View file @ c2d68045
......@@ -49,118 +49,61 @@ namespace {
* endianness at run time.
*/
/*
* A union which permits us to convert between a double and two 32 bit
* ints.
* TODO(jkummerow): This is undefined behavior. Use bit_cast instead.
*/
#if V8_TARGET_LITTLE_ENDIAN
union ieee_double_shape_type {
double value;
struct {
uint32_t lsw;
uint32_t msw;
} parts;
struct {
uint64_t w;
} xparts;
};
#else
union ieee_double_shape_type {
double value;
struct {
uint32_t msw;
uint32_t lsw;
} parts;
struct {
uint64_t w;
} xparts;
};
#endif
/* Get two 32 bit ints from a double. */
#define EXTRACT_WORDS(ix0, ix1, d) \
do { \
ieee_double_shape_type ew_u; \
ew_u.value = (d); \
(ix0) = ew_u.parts.msw; \
(ix1) = ew_u.parts.lsw; \
} while (false)
/* Get a 64-bit int from a double. */
#define EXTRACT_WORD64(ix, d) \
do { \
ieee_double_shape_type ew_u; \
ew_u.value = (d); \
(ix) = ew_u.xparts.w; \
#define EXTRACT_WORDS(ix0, ix1, d) \
do { \
uint64_t bits = bit_cast<uint64_t>(d); \
(ix0) = bits >> 32; \
(ix1) = bits & 0xFFFFFFFFu; \
} while (false)
/* Get the more significant 32 bit int from a double. */
#define GET_HIGH_WORD(i, d) \
do { \
ieee_double_shape_type gh_u; \
gh_u.value = (d); \
(i) = gh_u.parts.msw; \
#define GET_HIGH_WORD(i, d) \
do { \
uint64_t bits = bit_cast<uint64_t>(d); \
(i) = bits >> 32; \
} while (false)
/* Get the less significant 32 bit int from a double. */
#define GET_LOW_WORD(i, d) \
do { \
ieee_double_shape_type gl_u; \
gl_u.value = (d); \
(i) = gl_u.parts.lsw; \
#define GET_LOW_WORD(i, d) \
do { \
uint64_t bits = bit_cast<uint64_t>(d); \
(i) = bits & 0xFFFFFFFFu; \
} while (false)
/* Set a double from two 32 bit ints. */
#define INSERT_WORDS(d, ix0, ix1) \
do { \
ieee_double_shape_type iw_u; \
iw_u.parts.msw = (ix0); \
iw_u.parts.lsw = (ix1); \
(d) = iw_u.value; \
} while (false)
/* Set a double from a 64-bit int. */
#define INSERT_WORD64(d, ix) \
do { \
ieee_double_shape_type iw_u; \
iw_u.xparts.w = (ix); \
(d) = iw_u.value; \
#define INSERT_WORDS(d, ix0, ix1) \
do { \
uint64_t bits = 0; \
bits |= static_cast<uint64_t>(ix0) << 32; \
bits |= static_cast<uint32_t>(ix1); \
(d) = bit_cast<double>(bits); \
} while (false)
/* Set the more significant 32 bits of a double from an int. */
#define SET_HIGH_WORD(d, v) \
do { \
ieee_double_shape_type sh_u; \
sh_u.value = (d); \
sh_u.parts.msw = (v); \
(d) = sh_u.value; \
#define SET_HIGH_WORD(d, v) \
do { \
uint64_t bits = bit_cast<uint64_t>(d); \
bits &= V8_2PART_UINT64_C(0x00000000, FFFFFFFF); \
bits |= static_cast<uint64_t>(v) << 32; \
(d) = bit_cast<double>(bits); \
} while (false)
/* Set the less significant 32 bits of a double from an int. */
#define SET_LOW_WORD(d, v) \
do { \
ieee_double_shape_type sl_u; \
sl_u.value = (d); \
sl_u.parts.lsw = (v); \
(d) = sl_u.value; \
#define SET_LOW_WORD(d, v) \
do { \
uint64_t bits = bit_cast<uint64_t>(d); \
bits &= V8_2PART_UINT64_C(0xFFFFFFFF, 00000000); \
bits |= static_cast<uint32_t>(v); \
(d) = bit_cast<double>(bits); \
} while (false)
/* Support macro. */
#define STRICT_ASSIGN(type, lval, rval) ((lval) = (rval))
int32_t __ieee754_rem_pio2(double x, double* y) V8_WARN_UNUSED_RESULT;
double __kernel_cos(double x, double y) V8_WARN_UNUSED_RESULT;
int __kernel_rem_pio2(double* x, double* y, int e0, int nx, int prec,
......@@ -1559,7 +1502,7 @@ double exp(double x) {
hi = x - t * ln2HI[0]; /* t*ln2HI is exact here */
lo = t * ln2LO[0];
}
STRICT_ASSIGN(double, x, hi - lo);
x = hi - lo;
} else if (hx < 0x3E300000) { /* when |x|<2**-28 */
if (huge + x > one) return one + x; /* trigger inexact */
} else {
......@@ -1878,7 +1821,7 @@ double log1p(double x) {
if (hx >= 0x7FF00000) return x + x;
if (k != 0) {
if (hx < 0x43400000) {
STRICT_ASSIGN(double, u, 1.0 + x);
u = 1.0 + x;
GET_HIGH_WORD(hu, u);
k = (hu >> 20) - 1023;
c = (k > 0) ? 1.0 - (u - x) : x - (u - 1.0); /* correction term */
......@@ -2326,7 +2269,7 @@ double expm1(double x) {
hi = x - t * ln2_hi; /* t*ln2_hi is exact here */
lo = t * ln2_lo;
}
STRICT_ASSIGN(double, x, hi - lo);
x = hi - lo;
c = (hi - x) - lo;
} else if (hx < 0x3C900000) { /* when |x|<2**-54, return x */
t = huge + x; /* return x with inexact flags when x!=0 */
......@@ -2396,10 +2339,6 @@ double cbrt(double x) {
P4 = 0.145996192886612446982; /* 0x3FC2B000, 0xD4E4EDD7 */
int32_t hx;
union {
double value;
uint64_t bits;
} u;
double r, s, t = 0.0, w;
uint32_t sign;
uint32_t high, low;
......@@ -2457,9 +2396,9 @@ double cbrt(double x) {
* 0.667; the error in the rounded t can be up to about 3 23-bit ulps
* before the final error is larger than 0.667 ulps.
*/
u.value = t;
u.bits = (u.bits + 0x80000000) & 0xFFFFFFFFC0000000ULL;
t = u.value;
uint64_t bits = bit_cast<uint64_t>(t);
bits = (bits + 0x80000000) & 0xFFFFFFFFC0000000ULL;
t = bit_cast<double>(bits);
/* one step Newton iteration to 53 bits with error < 0.667 ulps */
s = t * t; /* t*t is exact */
......@@ -3070,14 +3009,11 @@ double tanh(double x) {
}
#undef EXTRACT_WORDS
#undef EXTRACT_WORD64
#undef GET_HIGH_WORD
#undef GET_LOW_WORD
#undef INSERT_WORDS
#undef INSERT_WORD64
#undef SET_HIGH_WORD
#undef SET_LOW_WORD
#undef STRICT_ASSIGN
} // namespace ieee754
} // namespace base
......
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