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SAHF/LAHF instructions are always available in 32-bit mode. Early 64-bit capable CPUs made the undefined opcodes in 64-bit mode. This was changed on later CPUs. We have a feature flag to control our usage of these instructions. This feature flag is hooked up to a clang command line option -msahf/-mno-sahf specifically to give control of the 64-bit mode behavior. In the backend X86Subtarget constructor we were explicitly forcing +sahf into the feature flag string if we were not compiling for 64-bit mode. This was intended to make the predicates always allow the instructions outside of 64-bit mode. Unfortunately, the way it was placed into the string allowed -mno-sahf from clang to disable SAHF instructions in 32-bit mode. This causes an assertion to fire if you compile a floating point comparison with something like "-march=pentium -mno-sahf" as our floating point comparison handling on CPUs that don't support FCOMI/FUCOMI instructions requires SAHF. To fix this, this commit restricts the feature flag to only apply to 64-bit mode by ignoring the flag outside 64-bit mode in X86Subtarget::hasLAHFSAHF(). This way we don't need to mess with the feature string at all. |
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| utils | ||
| .clang-format | ||
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| CMakeLists.txt | ||
| CODE_OWNERS.TXT | ||
| configure | ||
| CREDITS.TXT | ||
| LICENSE.TXT | ||
| llvm.spec.in | ||
| LLVMBuild.txt | ||
| README.txt | ||
| RELEASE_TESTERS.TXT | ||
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