[llvm] [DWARFLinker] Preserve DWARF discriminators while linking (PR #96124)
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Wed Jun 19 16:52:17 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-debuginfo
Author: David Tellenbach (dtellenbach)
<details>
<summary>Changes</summary>
DWARF-4 introduced DWARF discriminators but both, the classic and the parallel DWARF linkers discarded them so far.
After applying this patch dsymutil, which uses the DWARF linkers, correctly preserves discriminator information.
---
Full diff: https://github.com/llvm/llvm-project/pull/96124.diff
4 Files Affected:
- (modified) llvm/lib/DWARFLinker/Classic/DWARFStreamer.cpp (+13-4)
- (modified) llvm/lib/DWARFLinker/Parallel/DebugLineSectionEmitter.h (+10-4)
- (added) llvm/test/tools/dsymutil/Inputs/discriminator.arm64 ()
- (added) llvm/test/tools/dsymutil/discriminator.test (+39)
``````````diff
diff --git a/llvm/lib/DWARFLinker/Classic/DWARFStreamer.cpp b/llvm/lib/DWARFLinker/Classic/DWARFStreamer.cpp
index 8b31b5ead29ad..cc4ee2a1b4aec 100644
--- a/llvm/lib/DWARFLinker/Classic/DWARFStreamer.cpp
+++ b/llvm/lib/DWARFLinker/Classic/DWARFStreamer.cpp
@@ -1060,6 +1060,7 @@ void DwarfStreamer::emitLineTableRows(
unsigned FileNum = 1;
unsigned LastLine = 1;
unsigned Column = 0;
+ unsigned Discriminator = 0;
unsigned IsStatement = 1;
unsigned Isa = 0;
uint64_t Address = -1ULL;
@@ -1098,9 +1099,17 @@ void DwarfStreamer::emitLineTableRows(
MS->emitULEB128IntValue(Column);
LineSectionSize += 1 + getULEB128Size(Column);
}
-
- // FIXME: We should handle the discriminator here, but dsymutil doesn't
- // consider it, thus ignore it for now.
+ if (Discriminator != Row.Discriminator &&
+ MS->getContext().getDwarfVersion() >= 4) {
+ Discriminator = Row.Discriminator;
+ unsigned Size = getULEB128Size(Discriminator);
+ MS->emitIntValue(dwarf::DW_LNS_extended_op, 1);
+ MS->emitULEB128IntValue(Size + 1);
+ MS->emitIntValue(dwarf::DW_LNE_set_discriminator, 1);
+ MS->emitULEB128IntValue(Discriminator);
+ LineSectionSize += /* extended op */ 1 + getULEB128Size(Size + 1) +
+ /* discriminator */ 1 + Size;
+ }
if (Isa != Row.Isa) {
Isa = Row.Isa;
@@ -1156,7 +1165,7 @@ void DwarfStreamer::emitLineTableRows(
EncodingBuffer.resize(0);
Address = -1ULL;
LastLine = FileNum = IsStatement = 1;
- RowsSinceLastSequence = Column = Isa = 0;
+ RowsSinceLastSequence = Column = Discriminator = Isa = 0;
}
}
diff --git a/llvm/lib/DWARFLinker/Parallel/DebugLineSectionEmitter.h b/llvm/lib/DWARFLinker/Parallel/DebugLineSectionEmitter.h
index 1839164dcec17..0c4395589248a 100644
--- a/llvm/lib/DWARFLinker/Parallel/DebugLineSectionEmitter.h
+++ b/llvm/lib/DWARFLinker/Parallel/DebugLineSectionEmitter.h
@@ -315,6 +315,7 @@ class DebugLineSectionEmitter {
unsigned FileNum = 1;
unsigned LastLine = 1;
unsigned Column = 0;
+ unsigned Discriminator = 0;
unsigned IsStatement = 1;
unsigned Isa = 0;
uint64_t Address = -1ULL;
@@ -350,9 +351,14 @@ class DebugLineSectionEmitter {
Section.emitIntVal(dwarf::DW_LNS_set_column, 1);
encodeULEB128(Column, Section.OS);
}
-
- // FIXME: We should handle the discriminator here, but dsymutil doesn't
- // consider it, thus ignore it for now.
+ if (Discriminator != Row.Discriminator && MC->getDwarfVersion() >= 4) {
+ Discriminator = Row.Discriminator;
+ unsigned Size = getULEB128Size(Discriminator);
+ Section.emitIntVal(dwarf::DW_LNS_extended_op, 1);
+ encodeULEB128(Size + 1, Section.OS);
+ Section.emitIntVal(dwarf::DW_LNE_set_discriminator, 1);
+ encodeULEB128(Discriminator, Section.OS);
+ }
if (Isa != Row.Isa) {
Isa = Row.Isa;
@@ -397,7 +403,7 @@ class DebugLineSectionEmitter {
EncodingBuffer.resize(0);
Address = -1ULL;
LastLine = FileNum = IsStatement = 1;
- RowsSinceLastSequence = Column = Isa = 0;
+ RowsSinceLastSequence = Column = Discriminator = Isa = 0;
}
}
diff --git a/llvm/test/tools/dsymutil/Inputs/discriminator.arm64 b/llvm/test/tools/dsymutil/Inputs/discriminator.arm64
new file mode 100755
index 0000000000000..c48979fd8e9ff
Binary files /dev/null and b/llvm/test/tools/dsymutil/Inputs/discriminator.arm64 differ
diff --git a/llvm/test/tools/dsymutil/discriminator.test b/llvm/test/tools/dsymutil/discriminator.test
new file mode 100644
index 0000000000000..9bd1de2083567
--- /dev/null
+++ b/llvm/test/tools/dsymutil/discriminator.test
@@ -0,0 +1,39 @@
+; The DWARF at Inputs/discriminator.arm64 this test is based on was produced by
+; compiling
+;
+; __attribute__((noinline))
+; int foo(int a, int b, int c) {
+; int x = a ? b : c;
+; return x * a * b;
+; }
+;
+; int main(int argc, char** argv) {
+; return foo(argc, 2, 3);
+; }
+;
+; with -g -fdebug-info-for-profiling.
+
+RUN: dsymutil --flat --linker=classic -o - --verify-dwarf=none %p/Inputs/discriminator.arm64 | llvm-dwarfdump -debug-line - | FileCheck %s
+RUN: dsymutil --flat --linker=parallel -o - --verify-dwarf=none %p/Inputs/discriminator.arm64 | llvm-dwarfdump -debug-line - | FileCheck %s
+
+CHECK: Address Line Column File ISA Discriminator OpIndex Flags
+CHECK-NEXT: ------------------ ------ ------ ------ --- ------------- ------- -------------
+CHECK-NEXT: 0x0000000100003f14 2 0 0 0 0 0 is_stmt
+CHECK-NEXT: 0x0000000100003f24 3 11 0 0 0 0 is_stmt prologue_end
+CHECK-NEXT: 0x0000000100003f30 3 15 0 0 2 0
+CHECK-NEXT: 0x0000000100003f38 3 11 0 0 0 0
+CHECK-NEXT: 0x0000000100003f3c 3 19 0 0 4 0
+CHECK-NEXT: 0x0000000100003f44 3 11 0 0 0 0
+CHECK-NEXT: 0x0000000100003f48 0 11 0 0 0 0
+CHECK-NEXT: 0x0000000100003f4c 3 7 0 0 6 0
+CHECK-NEXT: 0x0000000100003f50 4 10 0 0 0 0 is_stmt
+CHECK-NEXT: 0x0000000100003f54 4 14 0 0 0 0
+CHECK-NEXT: 0x0000000100003f58 4 12 0 0 0 0
+CHECK-NEXT: 0x0000000100003f5c 4 18 0 0 0 0
+CHECK-NEXT: 0x0000000100003f60 4 16 0 0 0 0
+CHECK-NEXT: 0x0000000100003f64 4 3 0 0 0 0 epilogue_begin
+CHECK-NEXT: 0x0000000100003f6c 7 0 0 0 0 0 is_stmt
+CHECK-NEXT: 0x0000000100003f84 8 14 0 0 0 0 is_stmt prologue_end
+CHECK-NEXT: 0x0000000100003f88 8 10 0 0 0 0
+CHECK-NEXT: 0x0000000100003f94 8 3 0 0 0 0 epilogue_begin
+CHECK-NEXT: 0x0000000100003fa0 8 3 0 0 0 0 end_sequence
\ No newline at end of file
``````````
</details>
https://github.com/llvm/llvm-project/pull/96124
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