[EVM] Treat all .debug sections as DWO

This allows all DWARF debug sections to be emitted into a separate
debug-only object, keeping the runtime bytecode free of debug data.
SplitDwarfFile is explicitly disallowed, as it would produce both DWO and
non-DWO sections in the same debug-only object, which doesn't make sense
in our case.

Signed-off-by: Vladimir Radosavljevic <vr@matterlabs.dev>

Author: vladimirradosavljevic

llvm/lib/Target/EVM/MCTargetDesc/EVMAsmBackend.cpp

@@ -246,5 +246,7 @@ MCAsmBackend *llvm::createEVMMCAsmBackend(const Target &T,
                                           const MCSubtargetInfo &STI,
                                           const MCRegisterInfo &MRI,
                                           const MCTargetOptions &Options) {
+  if (!Options.SplitDwarfFile.empty())
+    report_fatal_error("EVM does not support split dwarf");
   return new EVMAsmBackend(T, STI, ELF::ELFOSABI_STANDALONE);
 }

llvm/lib/Target/EVM/MCTargetDesc/EVMELFObjectWriter.cpp

@@ -36,6 +36,10 @@ class EVMELFObjectWriter final : public MCELFObjectTargetWriter {
 
   unsigned getRelocType(const MCFixup &Fixup, const MCValue &Target,
                         bool IsPCRel) const override;
+
+  bool isDwoSection(const MCSectionELF &Sec) const override {
+    return Sec.getName().starts_with(".debug");
+  }
 };
 } // end of anonymous namespace
 

llvm/test/MC/EVM/split-dwarf-output.ll

@@ -0,0 +1,36 @@
+; RUN: llc -O2 -filetype=obj -split-dwarf-output=%t.dwo < %s | llvm-readobj --sections - | FileCheck %s --check-prefix=OBJ
+; RUN: llvm-readobj --sections %t.dwo | FileCheck %s --check-prefix=DWO
+; RUN: not --crash llc -O2 -filetype=obj -split-dwarf-file=foo.dwo -split-dwarf-output=%t.dwo < %s 2>&1 | FileCheck %s -check-prefix=SPLIT-NOT-SUPPORTED
+
+target datalayout = "E-p:256:256-i256:256:256-S256-a:256:256"
+target triple = "evm"
+
+; OBJ-NOT: Name: .debug
+; DWO: Name: .debug
+; SPLIT-NOT-SUPPORTED: LLVM ERROR: EVM does not support split dwarf
+
+define i256 @foo(i256 %0, i256 %1) !dbg !4 {
+  %add1 = add nsw i256 %0, 5, !dbg !7
+  %add2 = add nsw i256 %1, 3, !dbg !8
+  %mul = mul nsw i256 %add2, %add1, !dbg !9
+  %add3 = add nsw i256 %add2, %add1, !dbg !10
+  %add4 = add nsw i256 %add3, %mul, !dbg !11
+  ret i256 %add4, !dbg !12
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_Assembly, file: !1, isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false)
+!1 = !DIFile(filename: "Test.sol", directory: "/tmp")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !5, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!5 = !DISubroutineType(types: !6)
+!6 = !{}
+!7 = !DILocation(line: 2, column: 7, scope: !4)
+!8 = !DILocation(line: 3, column: 7, scope: !4)
+!9 = !DILocation(line: 4, column: 17, scope: !4)
+!10 = !DILocation(line: 5, column: 17, scope: !4)
+!11 = !DILocation(line: 6, column: 16, scope: !4)
+!12 = !DILocation(line: 6, column: 5, scope: !4)