[AArch64] New subtarget features to control ldp and stp formation, fo… #66098
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This is a new version, which was requested here: https://reviews.llvm.org/D159480 |
Thank you too for the tips! I am wondering if these x64 regressions in the checks are a thing or false positives, but I am going to have a real quick test tomorrow in a x64 machine. |
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After looking at that log generated by the ci, I realize I have to switch to debug build on x64 for that. Should be a test-issue. |
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The regression on my test case, caught by the ci, also happens with the upstream llvm (main branch) and has nothing to do with my changes. I see it is trigerred only for -mcpu=ampere1/ampere1a with the right test-case. Machine instruction Scheduler pass causes it on an assertion enabled with debug build. I should probably file a report on it. |
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Filed a report for the crash on: #66328 |
manosanaggh
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manosanaggh
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…cused on ampere1 and ampere1a. On some AArch64 cores, including Ampere's ampere1 and ampere1a architectures, load and store pair instructions are faster compared to simple loads/stores only when the alignment of the pair is at least twice that of the individual element being loaded. Based on that, this patch introduces four new subtarget features, two for controlling ldp and two for controlling stp, to cover the ampere1 and ampere1a alignment needs and to enable optional fine-grained control over ldp and stp generation in general. The latter can be utilized by another cpu, if there are possible benefits with a different policy than the default provided by the compiler. More specifically, for each of the ldp and stp respectively we have: - disable-ldp/disable-stp: Do not emit ldp/stp. - ldp-aligned-only/stp-aligned-only: Emit ldp/stp only if the source pointer is aligned to at least double the alignment of the type. Therefore, for -mcpu=ampere1 and -mcpu=ampere1a ldp-aligned-only/stp-aligned-only become the defaults because, of the benefit from the alignment, whereas for the rest of the cpus the default behaviour of the compiler is maintained.
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Thank you too! |
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There is hopefully a fix for the issues with the ampere1 model in #66384 @manosanaggh I didn't seem to be able to add you as a reviewer, but it would be good if you could take a look. Thanks |
Thanks, for addressing this quickly. I am going to have a look soon. Yes, you can't add me as a reviewer because of me not being a reviewer (not having rights in the project). |
…vm#66098) On some AArch64 cores, including Ampere's ampere1 and ampere1a architectures, load and store pair instructions are faster compared to simple loads/stores only when the alignment of the pair is at least twice that of the individual element being loaded. Based on that, this patch introduces four new subtarget features, two for controlling ldp and two for controlling stp, to cover the ampere1 and ampere1a alignment needs and to enable optional fine-grained control over ldp and stp generation in general. The latter can be utilized by another cpu, if there are possible benefits with a different policy than the default provided by the compiler. More specifically, for each of the ldp and stp respectively we have: - disable-ldp/disable-stp: Do not emit ldp/stp. - ldp-aligned-only/stp-aligned-only: Emit ldp/stp only if the source pointer is aligned to at least double the alignment of the type. Therefore, for -mcpu=ampere1 and -mcpu=ampere1a ldp-aligned-only/stp-aligned-only become the defaults, because of the benefit from the alignment, whereas for the rest of the cpus the default behaviour of the compiler is maintained.
…vm#66098) On some AArch64 cores, including Ampere's ampere1 and ampere1a architectures, load and store pair instructions are faster compared to simple loads/stores only when the alignment of the pair is at least twice that of the individual element being loaded. Based on that, this patch introduces four new subtarget features, two for controlling ldp and two for controlling stp, to cover the ampere1 and ampere1a alignment needs and to enable optional fine-grained control over ldp and stp generation in general. The latter can be utilized by another cpu, if there are possible benefits with a different policy than the default provided by the compiler. More specifically, for each of the ldp and stp respectively we have: - disable-ldp/disable-stp: Do not emit ldp/stp. - ldp-aligned-only/stp-aligned-only: Emit ldp/stp only if the source pointer is aligned to at least double the alignment of the type. Therefore, for -mcpu=ampere1 and -mcpu=ampere1a ldp-aligned-only/stp-aligned-only become the defaults, because of the benefit from the alignment, whereas for the rest of the cpus the default behaviour of the compiler is maintained.
…cused on ampere1 and ampere1a.
On some AArch64 cores, including Ampere's ampere1 and ampere1a architectures, load and store pair instructions are faster compared to simple loads/stores only when the alignment of the pair is at least twice that of the individual element being loaded.
Based on that, this patch introduces four new subtarget features, two for controlling ldp and two for controlling stp, to cover the ampere1 and ampere1a alignment needs and to enable optional fine-grained control over ldp and stp generation in general. The latter can be utilized by another cpu, if there are possible benefits
with a different policy than the default provided by the compiler.
More specifically, for each of the ldp and stp respectively we have:
Therefore, for -mcpu=ampere1 and -mcpu=ampere1a
ldp-aligned-only/stp-aligned-only become the defaults, because of the benefit from the alignment, whereas for the rest of the cpus the default behaviour of the compiler is maintained.