[all-commits] [llvm/llvm-project] 12b561: [bolt][aarch64] Change indirect call instrumentati...

[Alexey Moksyakov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 12b561a5e208655f31138d314f6af52ea785ee06
      https://github.com/llvm/llvm-project/commit/12b561a5e208655f31138d314f6af52ea785ee06
  Author: Alexey Moksyakov <moksyakov.alexey at huawei.com>
  Date:   2026-02-16 (Mon, 16 Feb 2026)

  Changed paths:
    M bolt/include/bolt/Core/MCPlusBuilder.h
    M bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp
    M bolt/lib/Target/RISCV/RISCVMCPlusBuilder.cpp
    M bolt/lib/Target/X86/X86MCPlusBuilder.cpp
    M bolt/runtime/instr.cpp
    M bolt/runtime/sys_aarch64.h
    M bolt/test/runtime/AArch64/instrumentation-ind-call.c

  Log Message:
  -----------
  [bolt][aarch64] Change indirect call instrumentation snippet (#180229)

Indirect call instrumentation snippet uses x16 register in exit handler
to go to destination target

    __bolt_instr_ind_call_handler_func:
            msr  nzcv, x1
            ldp  x0, x1, [sp], #16
            ldr  x16, [sp], #16
            ldp  x0, x1, [sp], #16
            br   x16	<-----

This patch adds the instrumentation snippet by calling instrumentation
runtime library through indirect call instruction and adding the wrapper
to store/load target value and the register for original indirect
instruction.

Example:
            mov x16, foo

    infirectCall:
            adrp x8, Label
            add  x8, x8, #:lo12:Label
            blr x8

Before:

    Instrumented indirect call:
            stp     x0, x1, [sp, #-16]!
            mov     x0, x8
            movk    x1, #0x0, lsl #48
            movk    x1, #0x0, lsl #32
            movk    x1, #0x0, lsl #16
            movk    x1, #0x0
            stp     x0, x1, [sp, #-16]!
            adrp    x0, __bolt_instr_ind_call_handler_func
            add     x0, x0, #:lo12:__bolt_instr_ind_call_handler_func
            blr     x0

    __bolt_instr_ind_call_handler:  (exit snippet)
            msr     nzcv, x1
            ldp     x0, x1, [sp], #16
            ldr     x16, [sp], #16
            ldp     x0, x1, [sp], #16
            br      x16    <- overwrites the original value in X16

    __bolt_instr_ind_call_handler_func:  (entry snippet)
            stp     x0, x1, [sp, #-16]!
            mrs     x1, nzcv
            adrp    x0, __bolt_instr_ind_call_handler
            add     x0, x0, x0, #:lo12:__bolt_instr_ind_call_handler
            ldr     x0, [x0]
            cmp     x0, #0x0
            b.eq    __bolt_instr_ind_call_handler
            str     x30, [sp, #-16]!
            blr     x0     <--- runtime lib store/load all regs
            ldr     x30, [sp], #16
            b       __bolt_instr_ind_call_handler


_________________________________________________________________________

After:

            mov     x16, foo
    infirectCall:
            adrp    x8, Label
            add     x8, x8, #:lo12:Label
            blr     x8

    Instrumented indirect call:
            stp     x0, x30, [sp, #-16]!
            mov     x0, callsiteid
            stp    x8, x0, [sp, #-16]!
            adrp    x8, __bolt_instr_ind_call_handler_func
            add     x8, x8, #:lo12:__bolt_instr_ind_call_handler_func
            blr     x8       <--- call trampoline instr lib
            ldr     x8, [sp], #16
            ldp     x0, x30, [sp], #16
            blr     x8       <--- original indirect call instruction

    // don't touch regs besides x0, x1
    __bolt_instr_ind_call_handler:  (exit snippet)
            ret     <---- return to original function with indirect call

    __bolt_instr_ind_call_handler_func: (entry snippet)
            adrp    x0, __bolt_instr_ind_call_handler
            add     x0, x0, #:lo12:__bolt_instr_ind_call_handler
            ldr     x0, [x0]
            cmp     x0, #0x0
            b.eq    __bolt_instr_ind_call_handler
            str     x30, [sp, #-16]!
            blr     x0     <--- runtime lib store/load all regs
            ldr     x30, [sp], #16
            b       __bolt_instr_ind_call_handler



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications