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Default enable attribute cx16 (-mattr=+cx16).

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This enables code generation for cmpxchg16b instruction which is
not available on very old 64bit CPUs.

The user can change this be choosing a different cpu (`-mcpu=...`)
or by explicitly disabling the attribute (`-mattr=-cx16`).
This commit is contained in:
Kai Nacke 2015-09-10 17:52:27 +02:00
parent 56482f8e30
commit 2cdbe58d86
1 changed files with 18 additions and 0 deletions
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18
driver/targetmachine.cpp
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@ -464,6 +464,24 @@ llvm::TargetMachine* createTargetMachine(
// to default to "generic").
cpu = getTargetCPU(cpu, triple);
// cmpxchg16b is not available on old 64bit CPUs. Enable code generation
// if the user did not make an explicit choice.
if (cpu == "x86-64")
{
#if LDC_LLVM_VER >= 304
const char* cx16_plus = "+cx16";
const char* cx16_minus = "-cx16";
#else
const char* cx16_plus = "+cmpxchg16b";
const char* cx16_minus = "-cmpxchg16b";
#endif
bool cx16 = false;
for (unsigned i = 0; i < attrs.size(); ++i)
if (attrs[i] == cx16_plus || attrs[i] == cx16_minus) cx16 = true;
if (!cx16)
features.AddFeature(cx16_plus);
}
if (Logger::enabled())
{
Logger::println("Targeting '%s' (CPU '%s' with features '%s')",