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Microsoft Specific
Tells the compiler not to insert Spectre variant 1 speculative execution barrier instructions for a function.
Syntax
__declspec( spectre(nomitigation) )
Remarks
The /Qspectre compiler option causes the compiler to insert speculative execution barrier instructions. They're inserted where analysis indicates that a Spectre variant 1 security vulnerability exists. The specific instructions emitted depend on the processor. While these instructions should have a minimal impact on code size or performance, there may be cases where your code is not affected by the vulnerability, and requires maximum performance.
Expert analysis might determine that a function is safe from a Spectre variant 1 bounds check bypass defect. In that case, you can suppress the generation of mitigation code within a function by applying __declspec(spectre(nomitigation)) to the function declaration.
Caution
The /Qspectre speculative execution barrier instructions provide important security protection and have a negligible affect on performance. Therefore, we recommend that you do not suppress them, except in the rare case where the performance of a function is a critical concern and the function is known to be safe.
Example
The following code shows how to use __declspec(spectre(nomitigation)).
// compile with: /c /Qspectre
static __declspec(spectre(nomitigation))
int noSpectreIssues() {
// No Spectre variant 1 vulnerability here
// ...
return 0;
}
int main() {
noSpectreIssues();
return 0;
}
END Microsoft Specific