50a97aacac
Re-commit of 32e8b550e5439c7e4aafa73894faffd5f25d0d05 This patch rearranges emission of CFI instructions, so the resulting DWARF and `.eh_frame` information is precise at every instruction. The current state is that the unwind info is emitted only after the function prologue. This is fine for synchronous (e.g. C++) exceptions, but the information is generally incorrect when the program counter is at an instruction in the prologue or the epilogue, for example: ``` stp x29, x30, [sp, #-16]! // 16-byte Folded Spill mov x29, sp .cfi_def_cfa w29, 16 ... ``` after the `stp` is executed the (initial) rule for the CFA still says the CFA is in the `sp`, even though it's already offset by 16 bytes A correct unwind info could look like: ``` stp x29, x30, [sp, #-16]! // 16-byte Folded Spill .cfi_def_cfa_offset 16 mov x29, sp .cfi_def_cfa w29, 16 ... ``` Having this information precise up to an instruction is useful for sampling profilers that would like to get a stack backtrace. The end goal (towards this patch is just a step) is to have fully working `-fasynchronous-unwind-tables`. Reviewed By: danielkiss, MaskRay Differential Revision: https://reviews.llvm.org/D111411
117 lines
3.4 KiB
LLVM
117 lines
3.4 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -verify-machineinstrs < %s -mtriple=aarch64-none-linux-gnu | FileCheck %s
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declare void @callee_stack0()
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declare void @callee_stack8([8 x i64], i64)
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declare void @callee_stack16([8 x i64], i64, i64)
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define dso_local void @caller_to0_from0() nounwind {
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; CHECK-LABEL: caller_to0_from0:
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; CHECK: // %bb.0:
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; CHECK-NEXT: b callee_stack0
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tail call void @callee_stack0()
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ret void
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}
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define dso_local void @caller_to0_from8([8 x i64], i64) nounwind{
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; CHECK-LABEL: caller_to0_from8:
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; CHECK: // %bb.0:
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; CHECK-NEXT: b callee_stack0
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tail call void @callee_stack0()
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ret void
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}
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define dso_local void @caller_to8_from0() {
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; CHECK-LABEL: caller_to8_from0:
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; CHECK: // %bb.0:
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; CHECK-NEXT: sub sp, sp, #32
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; CHECK-NEXT: .cfi_def_cfa_offset 32
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; CHECK-NEXT: str x30, [sp, #16] // 8-byte Folded Spill
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; CHECK-NEXT: .cfi_offset w30, -16
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; CHECK-NEXT: mov w8, #42
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; CHECK-NEXT: str x8, [sp]
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; CHECK-NEXT: bl callee_stack8
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; CHECK-NEXT: ldr x30, [sp, #16] // 8-byte Folded Reload
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; CHECK-NEXT: add sp, sp, #32
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; CHECK-NEXT: ret
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; Caller isn't going to clean up any extra stack we allocate, so it
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; can't be a tail call.
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tail call void @callee_stack8([8 x i64] undef, i64 42)
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ret void
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}
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define dso_local void @caller_to8_from8([8 x i64], i64 %a) {
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; CHECK-LABEL: caller_to8_from8:
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; CHECK: // %bb.0:
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; CHECK-NEXT: mov w8, #42
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; CHECK-NEXT: str x8, [sp]
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; CHECK-NEXT: b callee_stack8
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; This should reuse our stack area for the 42
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tail call void @callee_stack8([8 x i64] undef, i64 42)
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ret void
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}
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define dso_local void @caller_to16_from8([8 x i64], i64 %a) {
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; CHECK-LABEL: caller_to16_from8:
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; CHECK: // %bb.0:
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; CHECK-NEXT: sub sp, sp, #32
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; CHECK-NEXT: .cfi_def_cfa_offset 32
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; CHECK-NEXT: str x30, [sp, #16] // 8-byte Folded Spill
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; CHECK-NEXT: .cfi_offset w30, -16
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; CHECK-NEXT: bl callee_stack16
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; CHECK-NEXT: ldr x30, [sp, #16] // 8-byte Folded Reload
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; CHECK-NEXT: add sp, sp, #32
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; CHECK-NEXT: ret
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; Shouldn't be a tail call: we can't use SP+8 because our caller might
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; have something there. This may sound obvious but implementation does
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; some funky aligning.
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tail call void @callee_stack16([8 x i64] undef, i64 undef, i64 undef)
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ret void
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}
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define dso_local void @caller_to8_from24([8 x i64], i64 %a, i64 %b, i64 %c) {
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; CHECK-LABEL: caller_to8_from24:
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; CHECK: // %bb.0:
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; CHECK-NEXT: mov w8, #42
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; CHECK-NEXT: str x8, [sp]
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; CHECK-NEXT: b callee_stack8
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; Reuse our area, putting "42" at incoming sp
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tail call void @callee_stack8([8 x i64] undef, i64 42)
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ret void
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}
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define dso_local void @caller_to16_from16([8 x i64], i64 %a, i64 %b) {
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; CHECK-LABEL: caller_to16_from16:
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; CHECK: // %bb.0:
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; CHECK-NEXT: ldp x8, x9, [sp]
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; CHECK-NEXT: stp x9, x8, [sp]
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; CHECK-NEXT: b callee_stack16
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; Here we want to make sure that both loads happen before the stores:
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; otherwise either %a or %b will be wrongly clobbered.
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tail call void @callee_stack16([8 x i64] undef, i64 %b, i64 %a)
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ret void
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}
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@func = dso_local global void(i32)* null
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define dso_local void @indirect_tail() {
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; CHECK-LABEL: indirect_tail:
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; CHECK: // %bb.0:
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; CHECK-NEXT: adrp x8, func
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; CHECK-NEXT: mov w0, #42
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; CHECK-NEXT: ldr x1, [x8, :lo12:func]
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; CHECK-NEXT: br x1
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%fptr = load void(i32)*, void(i32)** @func
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tail call void %fptr(i32 42)
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ret void
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}
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