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jsm28bonzini
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target/i386: fix fbstp handling of out-of-range values
The fbstp implementation fails to check for out-of-range and invalid values, instead just taking the result of conversion to int64_t and storing its sign and low 18 decimal digits. Fix this by checking for an out-of-range result (invalid conversions always result in INT64_MAX or INT64_MIN from the softfloat code, which are large enough to be considered as out-of-range by this code) and storing the packed BCD indefinite encoding in that case. Signed-off-by: Joseph Myers <joseph@codesourcery.com> Message-Id: <alpine.DEB.2.21.2005132351110.11687@digraph.polyomino.org.uk> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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‎target/i386/fpu_helper.c‎

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -732,6 +732,16 @@ void helper_fbst_ST0(CPUX86State *env, target_ulong ptr)
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733733
val = floatx80_to_int64(ST0, &env->fp_status);
734734
mem_ref = ptr;
735+
if (val >= 1000000000000000000LL || val <= -1000000000000000000LL) {
736+
float_raise(float_flag_invalid, &env->fp_status);
737+
while (mem_ref < ptr + 7) {
738+
cpu_stb_data_ra(env, mem_ref++, 0, GETPC());
739+
}
740+
cpu_stb_data_ra(env, mem_ref++, 0xc0, GETPC());
741+
cpu_stb_data_ra(env, mem_ref++, 0xff, GETPC());
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cpu_stb_data_ra(env, mem_ref++, 0xff, GETPC());
743+
return;
744+
}
735745
mem_end = mem_ref + 9;
736746
if (SIGND(temp)) {
737747
cpu_stb_data_ra(env, mem_end, 0x80, GETPC());

‎tests/tcg/i386/test-i386-fbstp.c‎

Lines changed: 115 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,19 @@
11
/* Test fbstp instruction. */
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3+
#include <stdint.h>
34
#include <stdio.h>
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#include <string.h>
56

7+
union u {
8+
struct { uint64_t sig; uint16_t sign_exp; } s;
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long double ld;
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};
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volatile union u ld_invalid_1 = { .s = { 1, 1234 } };
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volatile union u ld_invalid_2 = { .s = { 0, 1234 } };
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volatile union u ld_invalid_3 = { .s = { 0, 0x7fff } };
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volatile union u ld_invalid_4 = { .s = { (UINT64_C(1) << 63) - 1, 0x7fff } };
16+
617
int main(void)
718
{
819
int ret = 0;
@@ -21,5 +32,109 @@ int main(void)
2132
printf("FAIL: fbstp -0.1\n");
2233
ret = 1;
2334
}
35+
memset(out, 0x1f, sizeof out);
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__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (-987654321987654321.0L) :
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"st");
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out[9] &= 0x80;
39+
if (memcmp(out, "\x21\x43\x65\x87\x19\x32\x54\x76\x98\x80",
40+
sizeof out) != 0) {
41+
printf("FAIL: fbstp -987654321987654321\n");
42+
ret = 1;
43+
}
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memset(out, 0x12, sizeof out);
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__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (999999999999999999.5L) :
46+
"st");
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if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
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printf("FAIL: fbstp 999999999999999999.5\n");
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ret = 1;
50+
}
51+
memset(out, 0x12, sizeof out);
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__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (1000000000000000000.0L) :
53+
"st");
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if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
55+
printf("FAIL: fbstp 1000000000000000000\n");
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ret = 1;
57+
}
58+
memset(out, 0x12, sizeof out);
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__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (1e30L) : "st");
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if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
61+
printf("FAIL: fbstp 1e30\n");
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ret = 1;
63+
}
64+
memset(out, 0x12, sizeof out);
65+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (-999999999999999999.5L) :
66+
"st");
67+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
68+
printf("FAIL: fbstp -999999999999999999.5\n");
69+
ret = 1;
70+
}
71+
memset(out, 0x12, sizeof out);
72+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (-1000000000000000000.0L) :
73+
"st");
74+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
75+
printf("FAIL: fbstp -1000000000000000000\n");
76+
ret = 1;
77+
}
78+
memset(out, 0x12, sizeof out);
79+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (-1e30L) : "st");
80+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
81+
printf("FAIL: fbstp -1e30\n");
82+
ret = 1;
83+
}
84+
memset(out, 0x12, sizeof out);
85+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (__builtin_infl()) : "st");
86+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
87+
printf("FAIL: fbstp inf\n");
88+
ret = 1;
89+
}
90+
memset(out, 0x12, sizeof out);
91+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (-__builtin_infl()) :
92+
"st");
93+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
94+
printf("FAIL: fbstp -inf\n");
95+
ret = 1;
96+
}
97+
memset(out, 0x12, sizeof out);
98+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (__builtin_nanl("")) :
99+
"st");
100+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
101+
printf("FAIL: fbstp nan\n");
102+
ret = 1;
103+
}
104+
memset(out, 0x12, sizeof out);
105+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (-__builtin_nanl("")) :
106+
"st");
107+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
108+
printf("FAIL: fbstp -nan\n");
109+
ret = 1;
110+
}
111+
memset(out, 0x12, sizeof out);
112+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (ld_invalid_1.ld) :
113+
"st");
114+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
115+
printf("FAIL: fbstp invalid 1\n");
116+
ret = 1;
117+
}
118+
memset(out, 0x12, sizeof out);
119+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (ld_invalid_2.ld) :
120+
"st");
121+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
122+
printf("FAIL: fbstp invalid 2\n");
123+
ret = 1;
124+
}
125+
memset(out, 0x12, sizeof out);
126+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (ld_invalid_3.ld) :
127+
"st");
128+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
129+
printf("FAIL: fbstp invalid 3\n");
130+
ret = 1;
131+
}
132+
memset(out, 0x12, sizeof out);
133+
__asm__ volatile ("fbstp %0" : "=m" (out) : "t" (ld_invalid_4.ld) :
134+
"st");
135+
if (memcmp(out, "\0\0\0\0\0\0\0\xc0\xff\xff", sizeof out) != 0) {
136+
printf("FAIL: fbstp invalid 4\n");
137+
ret = 1;
138+
}
24139
return ret;
25140
}

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