[PATCH] D95998: [Debug-Info] [NFC] use emitDwarfUnitLength to handle debug line section unit length field

[ChenZheng via Phabricator via llvm-commits]

shchenz updated this revision to Diff 323748.
shchenz added a comment.

1: address @ikudrin comments


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D95998/new/

https://reviews.llvm.org/D95998

Files:
  llvm/lib/MC/MCDwarf.cpp


Index: llvm/lib/MC/MCDwarf.cpp
===================================================================
--- llvm/lib/MC/MCDwarf.cpp
+++ llvm/lib/MC/MCDwarf.cpp
@@ -476,46 +476,33 @@
 
   // Create a symbol for the end of the section (to be set when we get there).
   MCSymbol *LineEndSym = context.createTempSymbol();
-
-  unsigned UnitLengthBytes =
-      dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
   unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());
 
-  if (context.getDwarfFormat() == dwarf::DWARF64)
-    // Emit DWARF64 mark.
-    MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);
-
-  // The length field does not include itself and, in case of the 64-bit DWARF
-  // format, the DWARF64 mark.
-  emitAbsValue(*MCOS,
-               makeEndMinusStartExpr(context, *LineStartSym, *LineEndSym,
-                                     UnitLengthBytes),
-               OffsetSize);
+  MCOS->emitDwarfUnitLength(LineEndSym, "unit length");
 
   // Next 2 bytes is the Version.
   unsigned LineTableVersion = context.getDwarfVersion();
   MCOS->emitInt16(LineTableVersion);
 
-  // Keep track of the bytes between the very start and where the header length
-  // comes out.
-  unsigned PreHeaderLengthBytes = UnitLengthBytes + 2;
-
   // In v5, we get address info next.
   if (LineTableVersion >= 5) {
     MCOS->emitInt8(context.getAsmInfo()->getCodePointerSize());
     MCOS->emitInt8(0); // Segment selector; same as EmitGenDwarfAranges.
-    PreHeaderLengthBytes += 2;
   }
 
+  MCSymbol *SymWithoutUnitLength = context.createTempSymbol("debug_line_");
+
   // Create a symbol for the end of the prologue (to be set when we get there).
   MCSymbol *ProEndSym = context.createTempSymbol(); // Lprologue_end
 
   // Length of the prologue, is the next 4 bytes (8 bytes for DWARF64). This is
   // actually the length from after the length word, to the end of the prologue.
-  emitAbsValue(*MCOS,
-               makeEndMinusStartExpr(context, *LineStartSym, *ProEndSym,
-                                     (PreHeaderLengthBytes + OffsetSize)),
-               OffsetSize);
+  emitAbsValue(
+      *MCOS,
+      makeEndMinusStartExpr(context, *SymWithoutUnitLength, *ProEndSym, 0),
+      OffsetSize);
+
+  MCOS->emitLabel(SymWithoutUnitLength);
 
   // Parameters of the state machine, are next.
   MCOS->emitInt8(context.getAsmInfo()->getMinInstAlignment());


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