Allow .alt_entry symbols to pass the .cfi nesting check #82268
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| @llvm/pr-subscribers-mc @llvm/pr-subscribers-backend-aarch64 Author: Jon Roelofs (jroelofs) ChangesFixes: #82261 Full diff: https://github.com/llvm/llvm-project/pull/82268.diff 2 Files Affected:
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp index 8e508dbdb1c69b..e8dc078c9610c2 100644 --- a/llvm/lib/MC/MCParser/AsmParser.cpp +++ b/llvm/lib/MC/MCParser/AsmParser.cpp @@ -44,6 +44,7 @@ #include "llvm/MC/MCSection.h" #include "llvm/MC/MCStreamer.h" #include "llvm/MC/MCSymbol.h" +#include "llvm/MC/MCSymbolMachO.h" #include "llvm/MC/MCTargetOptions.h" #include "llvm/MC/MCValue.h" #include "llvm/Support/Casting.h" @@ -1950,7 +1951,9 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info, Lex(); } - if (MAI.hasSubsectionsViaSymbols() && CFIStartProcLoc && Sym->isExternal()) + if (MAI.hasSubsectionsViaSymbols() && CFIStartProcLoc && + Sym->isExternal() && + (!isa<MCSymbolMachO>(Sym) || !cast<MCSymbolMachO>(Sym)->isAltEntry())) return Error(StartTokLoc, "non-private labels cannot appear between " ".cfi_startproc / .cfi_endproc pairs") && Error(*CFIStartProcLoc, "previous .cfi_startproc was here"); diff --git a/llvm/test/MC/AArch64/cfi-bad-nesting-darwin.s b/llvm/test/MC/AArch64/cfi-bad-nesting-darwin.s index 235b7d44809929..6a4dda3a77f05a 100644 --- a/llvm/test/MC/AArch64/cfi-bad-nesting-darwin.s +++ b/llvm/test/MC/AArch64/cfi-bad-nesting-darwin.s @@ -8,6 +8,8 @@ .p2align 2 _locomotive: .cfi_startproc +.alt_entry _engineer +_engineer: ret ; It is invalid to have a non-private label between .cfi_startproc and @@ -17,7 +19,7 @@ _locomotive: .p2align 2 _caboose: ; DARWIN: [[#@LINE-1]]:1: error: non-private labels cannot appear between .cfi_startproc / .cfi_endproc pairs -; DARWIN: [[#@LINE-10]]:2: error: previous .cfi_startproc was here +; DARWIN: [[#@LINE-12]]:2: error: previous .cfi_startproc was here ret .cfi_endproc |
MaskRay reviewed Feb 24, 2024
llvm/lib/MC/MCParser/AsmParser.cpp Outdated
| if (MAI.hasSubsectionsViaSymbols() && CFIStartProcLoc && Sym->isExternal()) | ||
| if (MAI.hasSubsectionsViaSymbols() && CFIStartProcLoc && | ||
| Sym->isExternal() && | ||
| (!isa<MCSymbolMachO>(Sym) || !cast<MCSymbolMachO>(Sym)->isAltEntry())) |
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Since only MCAsmInfoDarwin sets hasSubsectionsViaSymbols. The isa<MCSymbolMachO>(Sym) check is unneeded.
MaskRay approved these changes Feb 24, 2024
| .p2align2 | ||
| _locomotive: | ||
| .cfi_startproc | ||
| .alt_entry _engineer |
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Add a comment that a N_ALT_ENTRY symbol can be in the middle of a subsection?
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| This is a good candidate for release/18.x |
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| /cherry-pick 5b91647 |
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Error: Command failed due to missing milestone. |
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| /cherry-pick 5b91647 |
llvmbot pushed a commit to llvmbot/llvm-project that referenced this pull request Feb 28, 2024
A symbol with an `N_ALT_ENTRY` attribute may be defined in the middle of a subsection, so it is reasonable to opt them out of the `.cfi_{start,end}proc` nesting check. Fixes: llvm#82261 (cherry picked from commit 5b91647) Member
| /pull-request #83336 |
llvmbot pushed a commit to llvmbot/llvm-project that referenced this pull request Mar 11, 2024
A symbol with an `N_ALT_ENTRY` attribute may be defined in the middle of a subsection, so it is reasonable to opt them out of the `.cfi_{start,end}proc` nesting check. Fixes: llvm#82261 (cherry picked from commit 5b91647) 
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MaskRay added a commit that referenced this pull request Jul 2, 2024
The current `setAtom` is inaccurate: a `.alt_entry` label can also be recognized as an atom. This is mostly benign, but might cause two locations only separated by an `.alt_entry` to have different atoms. https://reviews.llvm.org/D153167 changed a `evaluateKnownAbsolute` to `evaluateAsAbsolute` and would not fold `A-B` even if they are only separated by a `.alt_entry` label, leading to a spurious error `invalid CFI advance_loc expression`. The fix is similar to #82268: add a special case for `.alt_entry`. Fix #97116 Pull Request: #97479
mylai-mtk pushed a commit to mylai-mtk/llvm-project that referenced this pull request Jul 12, 2024
A symbol with an `N_ALT_ENTRY` attribute may be defined in the middle of a subsection, so it is reasonable to opt them out of the `.cfi_{start,end}proc` nesting check. Fixes: llvm#82261 Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
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A symbol with an
N_ALT_ENTRYattribute may be defined in the middle of a subsection, so it is reasonable to opt them out of the.cfi_{start,end}procnesting check.Fixes: #82261