[CodeView] Fix inline sites that are missing code offsets.

[akhuang]

Summary

When an inline site has a starting code offset of 0, we sometimes
don't emit the starting offset.

This patch removes the case that emits a BinaryAnnotationOpCode::ChangeLineOffset when the code offset is 0. These cases will just go to the next case that emits a BinaryAnnotationOpCode::ChangeCodeOffsetAndLineOffset.

Bug: https://bugs.llvm.org/show_bug.cgi?id=48377

[dblaikie]

llvm/test/DebugInfo/COFF/inline-site-syms.ll

8–13 ↗

(On Diff #309308)

I'd probably suggest a simpler (it's probably about the same in IR, but simpler in terms of language features, names, etc) test case for inlining, something like:

void f1();
__attribute__((always_inline)) void f2() {
  f1();
}
void f3() {
  f2();
}

If that's adequate.

[rnk]

Is this a bug in llvm-symbolizer? What does windbg think if you stop on the first instruction of such an inline call site?

Looks like other test expectations need to be updated as well.

[akhuang]

Oh, I do need to fix the existing tests. Actually, the test I wrote probably belongs in that test directory.

I don't think it's a bug in llvm-symbolizer since I don't think we can assume that an inline site starts at offset 0 if it's not specified. llvm-symbolizer with DIA also fails to find the inline site here; I haven't looked at what windbg does.

[akhuang]

llvm/test/DebugInfo/COFF/inline-site-syms.ll

8–13 ↗

(On Diff #309308)

yep, I mostly used this particular code because the offset of the inline site in the function happens to be 0. But I suppose this should actually have been an assembly test and changing the existing tests should be adequate test coverage for this--

[akhuang]

Update failing tests

[rnk]

lgtm

llvm/lib/MC/MCCodeView.cpp

if (CurSourceLoc.File != LastSourceLoc.File) {
                                 ->getValue();
       compressAnnotation(BinaryAnnotationsOpCode::ChangeFile, Buffer);
       compressAnnotation(FileOffset, Buffer);
     }
 
     int LineDelta = CurSourceLoc.Line - LastSourceLoc.Line;
     unsigned EncodedLineDelta = encodeSignedNumber(LineDelta);
     unsigned CodeDelta = computeLabelDiff(Layout, LastLabel, Loc.getLabel());
-    if (CodeDelta == 0 && LineDelta != 0) {
-      compressAnnotation(BinaryAnnotationsOpCode::ChangeLineOffset, Buffer);
-      compressAnnotation(EncodedLineDelta, Buffer);
-    } else if (EncodedLineDelta < 0x8 && CodeDelta <= 0xf) {
+    if (EncodedLineDelta < 0x8 && CodeDelta <= 0xf) {
       // The ChangeCodeOffsetAndLineOffset combination opcode is used when the
       // encoded line delta uses 3 or fewer set bits and the code offset fits
       // in one nibble.
       unsigned Operand = (EncodedLineDelta << 4) | CodeDelta;
       compressAnnotation(BinaryAnnotationsOpCode::ChangeCodeOffsetAndLineOffset,
                          Buffer);
       compressAnnotation(Operand, Buffer);
     } else {

llvm/test/MC/COFF/cv-inline-linetable-infloop.s

 # RUN: llvm-mc -triple=x86_64-pc-win32 -filetype=obj < %s | llvm-readobj --codeview - | FileCheck %s
 
 # CHECK:    InlineSiteSym {
 # CHECK:      BinaryAnnotations [
-# CHECK:        ChangeLineOffset: 1
+# CHECK:        ChangeCodeOffsetAndLineOffset: {CodeOffset: 0x0, LineOffset: 1}
 # CHECK:        ChangeCodeLength: 0x2
 # CHECK:      ]
 # CHECK:    }
 
   .text
   .cv_file  1 "D:\\src\\llvm\\build\\t.c"
 
   .def   infloop;

llvm/test/MC/COFF/cv-loc-unreachable-2.s

 # ASM-NEXT:        c: ff 15 00 00 00 00             calll   *0
 #   } end inline
 
 # CODEVIEW: Inlinee |  Line | Source File
 # CODEVIEW:  0x1002 |     3 | C:\src\llvm-project\build\t.cpp (MD5: 0BC092F354CE14FDC2FA78F8EDE7426E)
 
 # CODEVIEW:      S_INLINESITE [size = 26]
 # CODEVIEW-NEXT: inlinee = 0x1002 (do_exit), parent = 0, end = 0
-# CODEVIEW-NEXT:   0602      line 1 (+1)
+# CODEVIEW-NEXT:   0B20      code 0x0 (+0x0) line 1 (+1)
 # CODEVIEW-NEXT:   0409      code end 0x9 (+0x9)
 # CODEVIEW-NEXT:   0B21      code 0xA (+0x1) line 2 (+1)
 # CODEVIEW-NEXT:   0B28      code 0x12 (+0x8) line 3 (+1)
 # CODEVIEW-NEXT:   0400      code end 0x12 (+0x0)
 
   .text
   .def   _callit; .scl  2; .type  32; .endef
   .globl  _callit                 # -- Begin function callit

llvm/test/MC/COFF/cv-loc-unreachable.s

 # ASM-NEXT:        c: ff 15 00 00 00 00             calll   *0
 #   } end inline
 
 # CODEVIEW: Inlinee |  Line | Source File
 # CODEVIEW:  0x1002 |     3 | C:\src\llvm-project\build\t.cpp (MD5: 0BC092F354CE14FDC2FA78F8EDE7426E)
 
 # CODEVIEW:      S_INLINESITE [size = 26]
 # CODEVIEW-NEXT: inlinee = 0x1002 (do_exit), parent = 0, end = 0
-# CODEVIEW-NEXT:   0602      line 1 (+1)
+# CODEVIEW-NEXT:   0B20      code 0x0 (+0x0) line 1 (+1)
 # CODEVIEW-NEXT:   0409      code end 0x9 (+0x9)
 # CODEVIEW-NEXT:   0B21      code 0xA (+0x1) line 2 (+1)
 # CODEVIEW-NEXT:   0B28      code 0x12 (+0x8) line 3 (+1)
 # CODEVIEW-NEXT:   0400      code end 0x12 (+0x0)
 
   .text
   .def   _callit; .scl  2; .type  32; .endef
   .globl  _callit                 # -- Begin function callit