[LLVMdev] how to annotate assembler

[Konstantin Vladimirov]

Hi,

In GCC there is one useful option -dp (or -dP for more verbose output)
to annotate assembler with instruction patterns, that was used when
assembler was generated. For example:

double
test(long long s)
{
  return s;
}

gcc -S -dp -O0 test.c

test:
.LFB0:
  .cfi_startproc
  pushq %rbp  # 18  *pushdi2_rex64/1  [length = 1]
  .cfi_def_cfa_offset 16
  movq  %rsp, %rbp  # 19  *movdi_1_rex64/2  [length = 3]
  .cfi_offset 6, -16
  .cfi_def_cfa_register 6
  movq  %rdi, -8(%rbp)  # 2 *movdi_1_rex64/4  [length = 4]
  cvtsi2sdq -8(%rbp), %xmm0 # 6 *floatdidf2_sse_interunit/2 [length = 6]
  leave # 24  leave_rex64 [length = 1]
  .cfi_def_cfa 7, 8
  ret # 25  return_internal [length = 1]
  .cfi_endproc

Now I may look into config/i386/i386.md, and look for mentioned
*pushdi2_rex64, movdi_1_rex64, floatdidf2_sse_interunit and other
patterns and study how they work.

How to make the same annotation for clang output assembler code?

test:
.Leh_func_begin1:
  pushq %rbp          # ??? what insn in X86InstrInfo.td?
.Llabel1:
  movq  %rsp, %rbp  # ??? what insn in X86InstrInfo.td?
.Llabel2:
  movq  %rdi, -16(%rbp)  # ??? what insn in X86InstrInfo.td?
  movq  -16(%rbp), %rax  # ??? what insn in X86InstrInfo.td?
  cvtsi2sdq %rax, %xmm0  # ??? what insn in X86InstrInfo.td?
  movsd %xmm0, -8(%rbp)  # ??? what insn in X86InstrInfo.td?
  movsd -8(%rbp), %xmm0  # ??? what insn in X86InstrInfo.td?
  popq  %rbp  # ??? what insn in X86InstrInfo.td?
  ret


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With best regards, Konstantin