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
66 lines
1.8 KiB
LLVM
66 lines
1.8 KiB
LLVM
; RUN: llc -verify-machineinstrs < %s -mtriple=aarch64-none-linux-gnu | FileCheck %s
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; RUN: llc -verify-machineinstrs < %s -mtriple=aarch64-none-linux-gnu -frame-pointer=all | FileCheck -check-prefix CHECK-WITHFP-ARM64 %s
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; Make sure a reasonably sane prologue and epilogue are
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; generated. This test is not robust in the face of an frame-handling
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; evolving, but still has value for unrelated changes, I
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; believe.
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;
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; In particular, it will fail when ldp/stp are used for frame setup,
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; when FP-elim is implemented, and when addressing from FP is
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; implemented.
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@var = global i64 0
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@local_addr = global i64* null
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declare void @foo()
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define void @trivial_func() nounwind {
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; CHECK-LABEL: trivial_func: // @trivial_func
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; CHECK-NEXT: // %bb.0
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; CHECK-NEXT: ret
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ret void
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}
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define void @trivial_fp_func() {
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; CHECK-LABEL: trivial_fp_func:
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; CHECK: str x30, [sp, #-16]!
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; CHECK-NOT: mov x29, sp
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; CHECK-WITHFP-ARM64-LABEL: trivial_fp_func:
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; CHECK-WITHFP-ARM64: stp x29, x30, [sp, #-16]!
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; CHECK-WITHFP-ARM64-NEXT: .cfi_def_cfa_offset 16
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; CHECK-WITHFP-ARM64-NEXT: mov x29, sp
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; CHECK-WITHFP-ARM64-NEXT: .cfi_def_cfa w29, 16
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; CHECK-WITHFP-ARM64-NEXT: .cfi_offset w30, -8
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; CHECK-WITHFP-ARM64-NEXT: .cfi_offset w29, -16
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; Dont't really care, but it would be a Bad Thing if this came after the epilogue.
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; CHECK-WITHFP-ARM64: bl foo
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; CHECK: bl foo
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call void @foo()
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ret void
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; CHECK: ldr x30, [sp], #16
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; CHECK-NEXT: ret
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; CHECK-WITHFP-ARM64: ldp x29, x30, [sp], #16
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; CHECK-WITHFP-ARM64-NEXT: ret
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}
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define void @stack_local() {
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%local_var = alloca i64
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; CHECK-LABEL: stack_local:
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; CHECK: sub sp, sp, #16
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%val = load i64, i64* @var
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store i64 %val, i64* %local_var
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; CHECK-DAG: str {{x[0-9]+}}, [sp, #{{[0-9]+}}]
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store i64* %local_var, i64** @local_addr
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; CHECK-DAG: add {{x[0-9]+}}, sp, #{{[0-9]+}}
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ret void
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}
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