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hoist the and out of the inline assembly

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gnzlbg 2018-06-24 22:03:15 +02:00 • committed by gnzlbg
parent 7affba30a5
commit 771dc9fd8e
1 changed files with 12 additions and 11 deletions
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23
library/stdarch/coresimd/x86/cpuid.rs
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@ -113,22 +113,23 @@ pub fn has_cpuid() -> bool {
# xor with the original eflags sets the bits that
# have been modified:
xor $0, $1
# There is a race between popfd (A) and pushfd (B)
# where other bits beyond 21st may have been modified due to
# interrupts, a debugger stepping through the asm, etc.
#
# Therefore, explicitly check whether the 21st bit
# was modified or not:
and $0, 0x200000
"#
: "=r"(result), "=r"(_temp)
:
: "cc", "memory"
: "intel");
// If result == 0, the 21st bit was not modified and cpuid is
// not available. If cpuid is available, the bit was modified and
// result != 0.
result != 0
// There is a race between popfd (A) and pushfd (B)
// where other bits beyond 21st may have been modified due to
// interrupts, a debugger stepping through the asm, etc.
//
// Therefore, explicitly check whether the 21st bit
// was modified or not.
//
// If the result is zero, the cpuid bit was not modified.
// If the result is 0x200000 (non-zero), then the cpuid
// was correctly modified and the CPU supports the cpuid
// instruction:
(result & 0x200000) != 0
}
}
}