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Work around a valgrind false-positive in CPUID.

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Valgrind versions prior to 3.17.0 assume that an uninitialized value
 in ECX causes the whole output of CPUID to be uninitialized, even
 though ECX is only "read" by CPUID for certain values of EAX.
Work around that by guaranteeing that ECX is initialized.
This commit is contained in:
Timothy B. Terriberry 2022-06-28 22:42:01 -07:00
parent 03889ae76d
commit 6577534a80
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GPG Key ID: 5A1149C19C699E4F
1 changed files with 8 additions and 4 deletions
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12
celt/x86/x86cpu.c
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@ -68,7 +68,8 @@ static void cpuid(unsigned int CPUInfo[4], unsigned int InfoType)
"=r" (CPUInfo[1]),
"=c" (CPUInfo[2]),
"=d" (CPUInfo[3]) :
"0" (InfoType)
/* We clear ECX to avoid a valgrind false-positive prior to v3.17.0. */
"0" (InfoType), "2" (0)
);
#else
__asm__ __volatile__ (
@ -77,12 +78,15 @@ static void cpuid(unsigned int CPUInfo[4], unsigned int InfoType)
"=b" (CPUInfo[1]),
"=c" (CPUInfo[2]),
"=d" (CPUInfo[3]) :
"0" (InfoType)
/* We clear ECX to avoid a valgrind false-positive prior to v3.17.0. */
"0" (InfoType), "2" (0)
);
#endif
#elif defined(CPU_INFO_BY_C)
if !(__get_cpuid(InfoType, &(CPUInfo[0]), &(CPUInfo[1]), &(CPUInfo[2]), &(CPUInfo[3]))) {
/* Our function cannot fail, but __get_cpuid can.
/* We use __get_cpuid_count to clear ECX to avoid a valgrind false-positive
prior to v3.17.0.*/
if (!__get_cpuid_count(InfoType, 0, &(CPUInfo[0]), &(CPUInfo[1]), &(CPUInfo[2]), &(CPUInfo[3]))) {
/* Our function cannot fail, but __get_cpuid{_count} can.
Returning all zeroes will effectively disable all SIMD, which is
what we want on CPUs that don't support CPUID. */
CPUInfo[3] = CPUInfo[2] = CPUInfo[1] = CPUInfo[0] = 0;