[bpf] fix dwarf elf relocs and line numbers

- teach RelocVisitor to recognize bpf relocations
- fix AsmInfo->PointerSize to make sure dwarf is emitted correctly
- add a test for the above

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 287521

llvm/include/llvm/Object/RelocVisitor.h

@@ -95,6 +95,17 @@ private:
           HasError = true;
           return RelocToApply();
         }
+      case Triple::bpfel:
+      case Triple::bpfeb:
+        switch (RelocType) {
+        case llvm::ELF::R_BPF_64_64:
+          return visitELF_BPF_64_64(R, Value);
+        case llvm::ELF::R_BPF_64_32:
+          return visitELF_BPF_64_32(R, Value);
+        default:
+          HasError = true;
+          return RelocToApply();
+        }
       case Triple::mips64el:
       case Triple::mips64:
         switch (RelocType) {
@@ -316,6 +327,15 @@ private:
     return RelocToApply(Res, 4);
   }
 
+  /// BPF ELF
+  RelocToApply visitELF_BPF_64_32(RelocationRef R, uint64_t Value) {
+    uint32_t Res = Value & 0xFFFFFFFF;
+    return RelocToApply(Res, 4);
+  }
+  RelocToApply visitELF_BPF_64_64(RelocationRef R, uint64_t Value) {
+    return RelocToApply(Value, 8);
+  }
+
   /// PPC64 ELF
   RelocToApply visitELF_PPC64_ADDR32(RelocationRef R, uint64_t Value) {
     int64_t Addend = getELFAddend(R);

llvm/include/llvm/Support/ELFRelocs/BPF.def

@@ -4,6 +4,5 @@
 
 // No relocation
 ELF_RELOC(R_BPF_NONE,        0)
-// Map index in "maps" section to file descriptor
-// within ld_64 instruction.
-ELF_RELOC(R_BPF_MAP_FD,      1)
+ELF_RELOC(R_BPF_64_64,       1)
+ELF_RELOC(R_BPF_64_32,      10)

llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp

@@ -41,13 +41,13 @@ unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
   default:
     llvm_unreachable("invalid fixup kind!");
   case FK_SecRel_8:
-    return ELF::R_X86_64_64;
+    return ELF::R_BPF_64_64;
   case FK_SecRel_4:
-    return ELF::R_X86_64_PC32;
+    return ELF::R_BPF_64_32;
   case FK_Data_8:
-    return IsPCRel ? ELF::R_X86_64_PC64 : ELF::R_X86_64_64;
+    return ELF::R_BPF_64_64;
   case FK_Data_4:
-    return IsPCRel ? ELF::R_X86_64_PC32 : ELF::R_X86_64_32;
+    return ELF::R_BPF_64_32;
   }
 }
 

llvm/lib/Target/BPF/MCTargetDesc/BPFMCAsmInfo.h

@@ -34,6 +34,15 @@ public:
     HasDotTypeDotSizeDirective = false;
 
     SupportsDebugInformation = true;
+    ExceptionsType = ExceptionHandling::DwarfCFI;
+    MinInstAlignment = 8;
+
+    // the default is 4 and it only affects dwarf elf output
+    // so if not set correctly, the dwarf data will be
+    // messed up in random places by 4 bytes. .debug_line
+    // section will be parsable, but with odd offsets and
+    // line numbers, etc.
+    PointerSize = 8;
   }
 };
 }

llvm/test/CodeGen/BPF/dwarfdump.ll

@@ -0,0 +1,58 @@
+; RUN: llc -O2 %s -o %t -filetype=obj
+; RUN: llvm-dwarfdump -debug-dump=line %t | FileCheck %s
+
+source_filename = "testprog.c"
+target datalayout = "e-m:e-p:64:64-i64:64-n32:64-S128"
+target triple = "bpf"
+
+@testprog.myvar_c = internal unnamed_addr global i32 0, align 4, !dbg !0
+
+define i32 @testprog(i32, i32) local_unnamed_addr #0 !dbg !1 {
+  tail call void @llvm.dbg.value(metadata i32 %0, i64 0, metadata !10, metadata !15), !dbg !16
+  tail call void @llvm.dbg.value(metadata i32 %1, i64 0, metadata !11, metadata !15), !dbg !17
+  %3 = load i32, i32* @testprog.myvar_c, align 4, !dbg !18, !tbaa !19
+  %4 = add i32 %1, %0, !dbg !23
+  %5 = add i32 %4, %3, !dbg !24
+  store i32 %5, i32* @testprog.myvar_c, align 4, !dbg !25, !tbaa !19
+  ret i32 %5, !dbg !26
+}
+
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!6}
+!llvm.module.flags = !{!12, !13}
+!llvm.ident = !{!14}
+
+!0 = distinct !DIGlobalVariable(name: "myvar_c", scope: !1, file: !2, line: 3, type: !5, isLocal: true, isDefinition: true)
+!1 = distinct !DISubprogram(name: "testprog", scope: !2, file: !2, line: 1, type: !3, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, unit: !6, variables: !9)
+!2 = !DIFile(filename: "testprog.c", directory: "/w/llvm/bld")
+!3 = !DISubroutineType(types: !4)
+!4 = !{!5, !5, !5}
+!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!6 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2, producer: "clang version 4.0.0 (trunk 287518) (llvm/trunk 287520)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !7, globals: !8)
+!7 = !{}
+!8 = !{!0}
+!9 = !{!10, !11}
+!10 = !DILocalVariable(name: "myvar_a", arg: 1, scope: !1, file: !2, line: 1, type: !5)
+!11 = !DILocalVariable(name: "myvar_b", arg: 2, scope: !1, file: !2, line: 1, type: !5)
+!12 = !{i32 2, !"Dwarf Version", i32 4}
+!13 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = !{!"clang version 4.0.0 (trunk 287518) (llvm/trunk 287520)"}
+!15 = !DIExpression()
+!16 = !DILocation(line: 1, column: 18, scope: !1)
+!17 = !DILocation(line: 1, column: 31, scope: !1)
+!18 = !DILocation(line: 5, column: 19, scope: !1)
+!19 = !{!20, !20, i64 0}
+!20 = !{!"int", !21, i64 0}
+!21 = !{!"omnipotent char", !22, i64 0}
+!22 = !{!"Simple C/C++ TBAA"}
+!23 = !DILocation(line: 5, column: 27, scope: !1)
+!24 = !DILocation(line: 7, column: 27, scope: !1)
+!25 = !DILocation(line: 7, column: 17, scope: !1)
+!26 = !DILocation(line: 9, column: 9, scope: !1)
+; CHECK: file_names[  1]    0 0x00000000 0x00000000 testprog.c
+; CHECK: 0x0000000000000000      2
+; CHECK: 0x0000000000000020      7