[llvm] Allow .alt_entry symbols to pass the .cfi nesting check (PR #82268)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-mc

@llvm/pr-subscribers-backend-aarch64

Author: Jon Roelofs (jroelofs)

<details>
<summary>Changes</summary>

Fixes: https://github.com/llvm/llvm-project/issues/82261

---
Full diff: https://github.com/llvm/llvm-project/pull/82268.diff


2 Files Affected:

- (modified) llvm/lib/MC/MCParser/AsmParser.cpp (+4-1) 
- (modified) llvm/test/MC/AArch64/cfi-bad-nesting-darwin.s (+3-1) 


``````````diff
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
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/82268