[PATCH] D81301: [X86] Emit two-byte NOP when possible
Fangrui Song via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 5 14:36:07 PDT 2020
MaskRay added inline comments.
================
Comment at: llvm/lib/Target/X86/X86MCInstLower.cpp:99
// Emit a minimal sequence of nops spanning NumBytes bytes.
-static void EmitNops(MCStreamer &OS, unsigned NumBytes, bool Is64Bit,
- const MCSubtargetInfo &STI);
+static void EmitNops(MCStreamer &OS, unsigned NumBytes,
+ const X86Subtarget *Subtarget);
----------------
Since you are changing the signature, you can rename it to emitNops as well to conform to the coding standards.
================
Comment at: llvm/lib/Target/X86/X86MCInstLower.cpp:1102
+ if (Subtarget->is32Bit() && NumBytes >= 2) {
+ OS.emitInstruction(
+ MCInstBuilder(X86::XCHG16ar).addReg(X86::AX).addReg(X86::AX),
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Can the x86-64 code path below be reused?
================
Comment at: llvm/test/CodeGen/X86/patchable-function-entry.ll:66
+; 32-COUNT-2: xchgw %ax, %ax
+; 32: nop
; 64: nopl 8(%rax,%rax)
----------------
32-NEXT
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D81301/new/
https://reviews.llvm.org/D81301
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