[XRay][compiler-rt][NFC] Deduplicate code in x86-64 trampolines.

[pelikan]

Summary

The layout of all registers saved on stack shouldn't deviate and will be reused in future trampolines as well.

While there, fix whitespace and clarify comments.

[dberris]

lib/xray/xray_trampoline_x86_64.S

16

Consider naming this SAVE_REGISTERS to make it a bit more natural to read.

35

Same idea here, as RESTORE_REGISTERS.

[pelikan]

• fix naming

[pelikan]

Macro names fixed.

lib/xray/xray_trampoline_x86_64.S

 //===-- xray_trampoline_x86.s -----------------------------------*- ASM -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of XRay, a dynamic runtime instrumentation system.
 //
 // This implements the X86-specific assembler for the trampolines.
 //
 //===----------------------------------------------------------------------===//
 
-  .text
-  .file "xray_trampoline_x86.S"
-  .globl __xray_FunctionEntry
-  .align 16, 0x90
-  .type __xray_FunctionEntry,@function
-
-__xray_FunctionEntry:
-  .cfi_startproc
-  // Save caller provided registers before doing any actual work.
-  pushq %rbp
-  .cfi_def_cfa_offset 16
+.macro SAVE_REGISTERS
   subq $200, %rsp
   movupd  %xmm0, 184(%rsp)
   movupd  %xmm1, 168(%rsp)
   movupd  %xmm2, 152(%rsp)
   movupd  %xmm3, 136(%rsp)
   movupd  %xmm4, 120(%rsp)
   movupd  %xmm5, 104(%rsp)
   movupd  %xmm6, 88(%rsp)
   movupd  %xmm7, 72(%rsp)
   movq  %rdi, 64(%rsp)
-  movq  %rax, 56(%rsp)
-  movq  %rdx, 48(%rsp)
+  movq  %rax, 56(%rsp)
+  movq  %rdx, 48(%rsp)
   movq  %rsi, 40(%rsp)
   movq  %rcx, 32(%rsp)
   movq  %r8, 24(%rsp)
   movq  %r9, 16(%rsp)
+.endm SAVE_REGISTERS
 
-  // de-mangled, that's __xray::XRayPatchedFunction, and we're doing an acquire
-  // load (on x86 is a normal mov instruction).
-  movq  _ZN6__xray19XRayPatchedFunctionE(%rip), %rax
-  testq %rax, %rax
-  je  .Ltmp0
-
-  // assume that %r10d has the function id.
-  movl  %r10d, %edi
-  xor %esi,%esi
-  callq *%rax
-.Ltmp0:
-  // restore the registers
+.macro RESTORE_REGISTERS
   movupd  184(%rsp), %xmm0
   movupd  168(%rsp), %xmm1
   movupd  152(%rsp), %xmm2
   movupd  136(%rsp), %xmm3
   movupd  120(%rsp), %xmm4
   movupd  104(%rsp), %xmm5
   movupd  88(%rsp) , %xmm6
   movupd  72(%rsp) , %xmm7
   movq  64(%rsp), %rdi
-  movq  56(%rsp), %rax
-  movq  48(%rsp), %rdx
+  movq  56(%rsp), %rax
+  movq  48(%rsp), %rdx
   movq  40(%rsp), %rsi
   movq  32(%rsp), %rcx
   movq  24(%rsp), %r8
   movq  16(%rsp), %r9
   addq  $200, %rsp
+.endm RESTORE_REGISTERS
+
+  .text
+  .file "xray_trampoline_x86.S"
+  .globl __xray_FunctionEntry
+  .align 16, 0x90
+  .type __xray_FunctionEntry,@function
+
+__xray_FunctionEntry:
+  .cfi_startproc
+  pushq %rbp
+  .cfi_def_cfa_offset 16
+  SAVE_REGISTERS
+
+  // This load has to be atomic, it's concurrent with __xray_patch().
+  // On x86/amd64, a simple (type-aligned) MOV instruction is enough.
+  movq  _ZN6__xray19XRayPatchedFunctionE(%rip), %rax
+  testq %rax, %rax
+  je  .Ltmp0
+
+  // The patched function prolog puts its xray_instr_map index into %r10d.
+  movl  %r10d, %edi
+  xor %esi,%esi
+  callq *%rax
+.Ltmp0:
+  RESTORE_REGISTERS
   popq  %rbp
   retq
 .Ltmp1:
   .size __xray_FunctionEntry, .Ltmp1-__xray_FunctionEntry
   .cfi_endproc
 
   .globl __xray_FunctionExit
   .align 16, 0x90
__xray_FunctionExit:
   movq  _ZN6__xray19XRayPatchedFunctionE(%rip), %rax
   testq %rax,%rax
   je  .Ltmp2
 
   movl  %r10d, %edi
   movl  $1, %esi
   callq *%rax
 .Ltmp2:
-  // Restore the important registers.
+  // Restore the important registers.
   movupd  40(%rsp), %xmm0
   movupd  24(%rsp), %xmm1
   movq  16(%rsp), %rax
   movq  8(%rsp), %rdx
   addq  $56, %rsp
   popq  %rbp
   retq
 .Ltmp3:
   .size __xray_FunctionExit, .Ltmp3-__xray_FunctionExit
   .cfi_endproc
 
   .global __xray_FunctionTailExit
   .align 16, 0x90
   .type __xray_FunctionTailExit,@function
 __xray_FunctionTailExit:
   .cfi_startproc
   // Save the important registers as in the entry trampoline, but indicate that
   // this is an exit. In the future, we will introduce a new entry type that
   // differentiates between a normal exit and a tail exit, but we'd have to do
   // this and increment the version number for the header.
   pushq %rbp
   .cfi_def_cfa_offset 16
-  subq $200, %rsp
-  movupd  %xmm0, 184(%rsp)
-  movupd  %xmm1, 168(%rsp)
-  movupd  %xmm2, 152(%rsp)
-  movupd  %xmm3, 136(%rsp)
-  movupd  %xmm4, 120(%rsp)
-  movupd  %xmm5, 104(%rsp)
-  movupd  %xmm6, 88(%rsp)
-  movupd  %xmm7, 72(%rsp)
-  movq  %rdi, 64(%rsp)
-  movq  %rax, 56(%rsp)
-  movq  %rdx, 48(%rsp)
-  movq  %rsi, 40(%rsp)
-  movq  %rcx, 32(%rsp)
-  movq  %r8, 24(%rsp)
-  movq  %r9, 16(%rsp)
+  SAVE_REGISTERS
 
   movq  _ZN6__xray19XRayPatchedFunctionE(%rip), %rax
   testq %rax,%rax
   je  .Ltmp4
 
   movl  %r10d, %edi
   movl  $1, %esi
   callq *%rax
 
 .Ltmp4:
-  // Restore the registers.
-  movupd  184(%rsp), %xmm0
-  movupd  168(%rsp), %xmm1
-  movupd  152(%rsp), %xmm2
-  movupd  136(%rsp), %xmm3
-  movupd  120(%rsp), %xmm4
-  movupd  104(%rsp), %xmm5
-  movupd  88(%rsp) , %xmm6
-  movupd  72(%rsp) , %xmm7
-  movq  64(%rsp), %rdi
-  movq  56(%rsp), %rax
-  movq  48(%rsp), %rdx
-  movq  40(%rsp), %rsi
-  movq  32(%rsp), %rcx
-  movq  24(%rsp), %r8
-  movq  16(%rsp), %r9
-  addq  $200, %rsp
+  RESTORE_REGISTERS
   popq  %rbp
   retq
 .Ltmp5:
-  .size __xray_FunctionTailExit, .Ltmp5-__xray_FunctionTailExit
+  .size __xray_FunctionTailExit, .Ltmp5-__xray_FunctionTailExit
   .cfi_endproc