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
63 lines
2.3 KiB
LLVM
63 lines
2.3 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc < %s -mtriple=arm64-apple-ios -relocation-model=pic -frame-pointer=all | FileCheck %s
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@__stack_chk_guard = external global i64*
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; PR20558
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; Load the stack guard for the second time, just in case the previous value gets spilled.
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define i32 @test_stack_guard_remat2() ssp {
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; CHECK-LABEL: test_stack_guard_remat2:
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; CHECK: ; %bb.0: ; %entry
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; CHECK-NEXT: sub sp, sp, #64
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; CHECK-NEXT: .cfi_def_cfa_offset 64
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; CHECK-NEXT: stp x29, x30, [sp, #48] ; 16-byte Folded Spill
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; CHECK-NEXT: add x29, sp, #48
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; CHECK-NEXT: .cfi_def_cfa w29, 16
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; CHECK-NEXT: .cfi_offset w30, -8
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; CHECK-NEXT: .cfi_offset w29, -16
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; CHECK-NEXT: Lloh0:
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; CHECK-NEXT: adrp x8, ___stack_chk_guard@GOTPAGE
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; CHECK-NEXT: Lloh1:
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; CHECK-NEXT: adrp x9, ___stack_chk_guard@GOTPAGE
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; CHECK-NEXT: Lloh2:
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; CHECK-NEXT: ldr x8, [x8, ___stack_chk_guard@GOTPAGEOFF]
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; CHECK-NEXT: Lloh3:
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; CHECK-NEXT: ldr x9, [x9, ___stack_chk_guard@GOTPAGEOFF]
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; CHECK-NEXT: Lloh4:
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; CHECK-NEXT: ldr x8, [x8]
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; CHECK-NEXT: Lloh5:
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; CHECK-NEXT: ldr x9, [x9]
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; CHECK-NEXT: str x8, [sp]
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; CHECK-NEXT: Lloh6:
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; CHECK-NEXT: adrp x8, ___stack_chk_guard@GOTPAGE
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; CHECK-NEXT: stur x9, [x29, #-8]
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; CHECK-NEXT: Lloh7:
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; CHECK-NEXT: ldr x8, [x8, ___stack_chk_guard@GOTPAGEOFF]
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; CHECK-NEXT: ldur x9, [x29, #-8]
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; CHECK-NEXT: Lloh8:
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; CHECK-NEXT: ldr x8, [x8]
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; CHECK-NEXT: cmp x8, x9
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; CHECK-NEXT: b.ne LBB0_2
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; CHECK-NEXT: ; %bb.1: ; %entry
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; CHECK-NEXT: ldp x29, x30, [sp, #48] ; 16-byte Folded Reload
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; CHECK-NEXT: mov w0, #-1
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; CHECK-NEXT: add sp, sp, #64
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; CHECK-NEXT: ret
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; CHECK-NEXT: LBB0_2: ; %entry
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; CHECK-NEXT: bl ___stack_chk_fail
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; CHECK-NEXT: .loh AdrpLdrGotLdr Lloh6, Lloh7, Lloh8
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; CHECK-NEXT: .loh AdrpLdrGotLdr Lloh1, Lloh3, Lloh5
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; CHECK-NEXT: .loh AdrpLdrGotLdr Lloh0, Lloh2, Lloh4
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entry:
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%StackGuardSlot = alloca i8*
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%StackGuard = load i8*, i8** bitcast (i64** @__stack_chk_guard to i8**)
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call void @llvm.stackprotector(i8* %StackGuard, i8** %StackGuardSlot)
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%container = alloca [32 x i8], align 1
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call void @llvm.stackprotectorcheck(i8** bitcast (i64** @__stack_chk_guard to i8**))
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ret i32 -1
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}
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declare void @llvm.stackprotector(i8*, i8**) ssp
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declare void @llvm.stackprotectorcheck(i8**) ssp
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