[llvm-dev] How to find out the default CPU / Features String for a given triple?
Andrew Kelley via llvm-dev
llvm-dev at lists.llvm.org
Wed Jan 22 22:49:35 PST 2020
When I pass an empty string for cpu and features to createTargetMachine,
and then use LLVMGetTargetMachineCPU() and
LLVMGetTargetMachineFeatureString() to get the strings back, they are
still empty. Is there a way to have llvm compute the effective
cpu/features string, and provide it so that I can inspect it?
I'm trying to figure out how the cpu/features string that I am
explicitly passing, which I am expecting to be equivalent to passing
empty string, is different.
As an example, I have a test passing in the CI using the triple
"aarch64v8.1a-unknown-linux-unknown", and "" for both CPU name and
target features string. However when I pass the following target
specific features string, I get qemu crashing in the CI:
Now, I understand that qemu crashing can be fixed by using a newer qemu
version. And, indeed, on my laptop with a newer qemu, the test passes.
However, this test was previously passing on the CI, which means that
with this explicit string of target specific features, *something is
different*. I am trying to determine what that different thing is.
Thanks in advance for the help,
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