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target/i386: fix fxam handling of invalid encodings 

The fxam implementation does not check for invalid encodings, instead
treating them like NaN or normal numbers depending on the exponent.
Fix it to check that the high bit of the significand is set before
treating an encoding as NaN or normal, thus resulting in correct
handling (all of C0, C2 and C3 cleared) for invalid encodings.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Message-Id: <alpine.DEB.2.21.2005132349311.11687@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Joseph Myers 2020-05-13 23:50:19 +00:00 committed by Paolo Bonzini
parent 80b4008c80
commit 34b9cc076f
2 changed files with 145 additions and 2 deletions
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4
target/i386/fpu_helper.c
View File

@ -1099,7 +1099,7 @@ void helper_fxam_ST0(CPUX86State *env)
if (expdif == MAXEXPD) {
if (MANTD(temp) == 0x8000000000000000ULL) {
env->fpus |= 0x500; /* Infinity */
} else {
} else if (MANTD(temp) & 0x8000000000000000ULL) {
env->fpus |= 0x100; /* NaN */
}
} else if (expdif == 0) {
@ -1108,7 +1108,7 @@ void helper_fxam_ST0(CPUX86State *env)
} else {
env->fpus |= 0x4400; /* Denormal */
}
} else {
} else if (MANTD(temp) & 0x8000000000000000ULL) {
env->fpus |= 0x400;
}
}

143
tests/tcg/i386/test-i386-fxam.c Normal file
View File

@ -0,0 +1,143 @@
/* Test fxam instruction. */
#include <stdint.h>
#include <stdio.h>
union u {
struct { uint64_t sig; uint16_t sign_exp; } s;
long double ld;
};
volatile union u ld_pseudo_m16382 = { .s = { UINT64_C(1) << 63, 0 } };
volatile union u ld_pseudo_nm16382 = { .s = { UINT64_C(1) << 63, 0x8000 } };
volatile union u ld_invalid_1 = { .s = { 1, 1234 } };
volatile union u ld_invalid_2 = { .s = { 0, 1234 } };
volatile union u ld_invalid_3 = { .s = { 0, 0x7fff } };
volatile union u ld_invalid_4 = { .s = { (UINT64_C(1) << 63) - 1, 0x7fff } };
volatile union u ld_invalid_n1 = { .s = { 1, 0x8123 } };
volatile union u ld_invalid_n2 = { .s = { 0, 0x8123 } };
volatile union u ld_invalid_n3 = { .s = { 0, 0xffff } };
volatile union u ld_invalid_n4 = { .s = { (UINT64_C(1) << 63) - 1, 0xffff } };
#define C0 (1 << 8)
#define C1 (1 << 9)
#define C2 (1 << 10)
#define C3 (1 << 14)
#define FLAGS (C0 | C1 | C2 | C3)
int main(void)
{
short sw;
int ret = 0;
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (0.0L));
if ((sw & FLAGS) != C3) {
printf("FAIL: +0\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (-0.0L));
if ((sw & FLAGS) != (C3 | C1)) {
printf("FAIL: -0\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (1.0L));
if ((sw & FLAGS) != C2) {
printf("FAIL: +normal\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (-1.0L));
if ((sw & FLAGS) != (C2 | C1)) {
printf("FAIL: -normal\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (__builtin_infl()));
if ((sw & FLAGS) != (C2 | C0)) {
printf("FAIL: +inf\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (-__builtin_infl()));
if ((sw & FLAGS) != (C2 | C1 | C0)) {
printf("FAIL: -inf\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (__builtin_nanl("")));
if ((sw & FLAGS) != C0) {
printf("FAIL: +nan\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (-__builtin_nanl("")));
if ((sw & FLAGS) != (C1 | C0)) {
printf("FAIL: -nan\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (__builtin_nansl("")));
if ((sw & FLAGS) != C0) {
printf("FAIL: +snan\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (-__builtin_nansl("")));
if ((sw & FLAGS) != (C1 | C0)) {
printf("FAIL: -snan\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (0x1p-16445L));
if ((sw & FLAGS) != (C3 | C2)) {
printf("FAIL: +denormal\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (-0x1p-16445L));
if ((sw & FLAGS) != (C3 | C2 | C1)) {
printf("FAIL: -denormal\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_pseudo_m16382.ld));
if ((sw & FLAGS) != (C3 | C2)) {
printf("FAIL: +pseudo-denormal\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_pseudo_nm16382.ld));
if ((sw & FLAGS) != (C3 | C2 | C1)) {
printf("FAIL: -pseudo-denormal\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_1.ld));
if ((sw & FLAGS) != 0) {
printf("FAIL: +invalid 1\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_n1.ld));
if ((sw & FLAGS) != C1) {
printf("FAIL: -invalid 1\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_2.ld));
if ((sw & FLAGS) != 0) {
printf("FAIL: +invalid 2\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_n2.ld));
if ((sw & FLAGS) != C1) {
printf("FAIL: -invalid 2\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_3.ld));
if ((sw & FLAGS) != 0) {
printf("FAIL: +invalid 3\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_n3.ld));
if ((sw & FLAGS) != C1) {
printf("FAIL: -invalid 3\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_4.ld));
if ((sw & FLAGS) != 0) {
printf("FAIL: +invalid 4\n");
ret = 1;
}
__asm__ volatile ("fxam\nfnstsw" : "=a" (sw) : "t" (ld_invalid_n4.ld));
if ((sw & FLAGS) != C1) {
printf("FAIL: -invalid 4\n");
ret = 1;
}
return ret;
}