[PATCH] D147980: Emit unwind information in .debug_frame section when .cfi_sections .debug_frame intrinsic is used

[Shubham Sandeep Rastogi via Phabricator via llvm-commits]

rastogishubham updated this revision to Diff 513383.
rastogishubham added a comment.

I addressed the review feedback about clarifying the comment I had written for when to skip emitting the FDEs and CIEs


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147980/new/

https://reviews.llvm.org/D147980

Files:
  llvm/lib/MC/MCDwarf.cpp
  llvm/test/DebugInfo/AArch64/debugframeinfo.s


Index: llvm/test/DebugInfo/AArch64/debugframeinfo.s
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/AArch64/debugframeinfo.s
@@ -0,0 +1,43 @@
+# RUN: llvm-mc -filetype=obj --triple=arm64-apple-darwin22.1.0 %s -o %t.o
+# RUN: llvm-dwarfdump -debug-frame %t.o | FileCheck %s
+
+# CHECK: .debug_frame contents:
+# CHECK-EMPTY: 
+# CHECK-NEXT: 00000000 00000014 ffffffff CIE
+# CHECK-NEXT: Format:                DWARF32
+# CHECK-NEXT: Version:               4
+# CHECK-NEXT: Augmentation:          ""
+# CHECK-NEXT: Address size:          8
+# CHECK-NEXT: Segment desc size:     0
+# CHECK-NEXT: Code alignment factor: 1
+# CHECK-NEXT: Data alignment factor: -8
+# CHECK-NEXT: Return address column: 30
+# CHECK-EMPTY: 
+# CHECK-NEXT: DW_CFA_def_cfa: WSP +0
+# CHECK-NEXT: DW_CFA_nop:
+# CHECK-NEXT: DW_CFA_nop:
+# CHECK-NEXT: DW_CFA_nop:
+# CHECK-NEXT: DW_CFA_nop:
+# CHECK-NEXT: DW_CFA_nop:
+# CHECK-NEXT: DW_CFA_nop:
+# CHECK-EMPTY: 
+# CHECK-NEXT: CFA=WSP
+# CHECK-EMPTY: 
+# CHECK-NEXT: 00000018 00000014 00000000 FDE cie=00000000 pc=00000000...00000000
+# CHECK-NEXT: Format:       DWARF32
+# CHECK-EMPTY: 
+# CHECK-NEXT: 0x0: CFA=WSP
+
+# CHECK: .eh_frame contents:
+# CHECK-EMPTY:
+# CHECK-EMPTY:
+
+        .cfi_sections .debug_frame
+        .cfi_startproc
+        .cfi_personality 0x9b, g
+        .cfi_lsda 0x1b, h
+        .cfi_endproc
+        .global g
+g:
+        .global h
+h:
Index: llvm/lib/MC/MCDwarf.cpp
===================================================================
--- llvm/lib/MC/MCDwarf.cpp
+++ llvm/lib/MC/MCDwarf.cpp
@@ -1876,7 +1876,11 @@
     }
   }
 
-  if (!NeedsEHFrameSection) return;
+  // Compact unwind information can be emitted in the eh_frame section or the
+  // debug_frame section. Skip emitting FDEs and CIEs when the compact unwind
+  // doesn't need an eh_frame section and the emission location is the eh_frame
+  // section.
+  if (!NeedsEHFrameSection && IsEH) return;
 
   MCSection &Section =
       IsEH ? *const_cast<MCObjectFileInfo *>(MOFI)->getEHFrameSection()
@@ -1903,9 +1907,13 @@
     const MCDwarfFrameInfo &Frame = *I;
     ++I;
     if (CanOmitDwarf && Frame.CompactUnwindEncoding !=
-          MOFI->getCompactUnwindDwarfEHFrameOnly())
-      // Don't generate an EH frame if we don't need one. I.e., it's taken care
-      // of by the compact unwind encoding.
+          MOFI->getCompactUnwindDwarfEHFrameOnly() && IsEH)
+      // CIEs and FDEs can be emitted in either the eh_frame section or the
+      // debug_frame section, on some platforms (e.g. AArch64) the target object
+      // file supports emitting a compact_unwind section without an associated
+      // eh_frame section. If the eh_frame section is not needed, and the
+      // location where the CIEs and FDEs are to be emitted is the eh_frame
+      // section, do not emit anything.
       continue;
 
     CIEKey Key(Frame);


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