[PATCH] D80163: [X86][VARARG] Avoid spilling xmm registers for va_start.

Tue Mar 2 06:35:47 PST 2021

avl added inline comments.

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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:3490
+        // VASTART_SAVE_XMM_REGS to avoid unneccessary spilling.
+        TheMachineFunction.getRegInfo().addLiveIn(Reg);
+        LiveXMMRegs.push_back(DAG.getRegister(Reg, MVT::v4f32));
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pengfei wrote:
> Does the change affect GreedyRA?
Yes, it does. GreedyRA might have the same problem if it would generate a spill in entry block for the xmm varargs. Though, it would probably be some specific artificial case(in contrast to FastRA which always spills live ranges on the block boundary).

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Comment at: llvm/test/CodeGen/X86/xmm-vararg-noopt.ll:1
+; RUN: llc -O0 -mtriple=x86_64-unknown-unknown < %s | FileCheck %s
+
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pengfei wrote:
> Maybe we can also generate the test by update_llc_test_checks?
Ok, will do that way.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80163/new/

https://reviews.llvm.org/D80163