[PATCH] D143425: Reland "[X86][ABI] Don't preserve return regs for preserve_all/preserve_most CCs""

[Anton Bikineev via Phabricator via llvm-commits]

AntonBikineev added a comment.

In D143425#4113345 <https://reviews.llvm.org/D143425#4113345>, @goldstein.w.n wrote:

> should there be a test with avx512 for `xmm16-31`?

Actually, `preserve_all` doesn't preserve them, which is apparently missing, since the CCs were introduced short after AVX512 was proposed. It would probably make sense to introduce

  def CSR_64_RT_AllRegs_AVX512 : CalleeSavedRegs<(add CSR_64_RT_MostRegs,
                                                 (sequence "ZMM%u", 0, 31))>;

but I believe it should go to a separate change.



================
Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:3388
+        CallConv != CallingConv::PreserveAll &&
+        CallConv != CallingConv::PreserveMost)
       MF.getRegInfo().disableCalleeSavedRegister(RetValReg);
----------------
goldstein.w.n wrote:
> `CallConv ==  CallingConv::X86_RegCall`
This would also need `|| MF.getFunction().hasFnAttribute("no_caller_saved_registers")`, so I don't think it'd be more readable overall.


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https://reviews.llvm.org/D143425