[DebugInfo] Generate fixups as emitting DWARF .debug_line.

It is necessary to generate fixups in .debug_line as relaxation is
enabled due to the address delta may be changed after relaxation.

DWARF will record the mappings of lines and addresses in
.debug_line section. It will encode the information using special
opcodes, standard opcodes and extended opcodes in Line Number
Program. I use DW_LNS_fixed_advance_pc to encode fixed length
address delta and DW_LNE_set_address to encode absolute address
to make it possible to generate fixups in .debug_line section.

Differential Revision: https://reviews.llvm.org/D46850

llvm-svn: 338477

2 files changed, 77 insertions, 0 deletions

diff --git a/llvm/test/DebugInfo/RISCV/lit.local.cfg b/llvm/test/DebugInfo/RISCV/lit.local.cfg
new file mode 100644
index 00000000000..c63820126f8
--- /dev/null
+++ b/llvm/test/DebugInfo/RISCV/lit.local.cfg
@@ -0,0 +1,2 @@
+if not 'RISCV' in config.root.targets:
+    config.unsupported = True
diff --git a/llvm/test/DebugInfo/RISCV/relax-debug-line.ll b/llvm/test/DebugInfo/RISCV/relax-debug-line.ll
new file mode 100644
index 00000000000..814b253fadf
--- /dev/null
+++ b/llvm/test/DebugInfo/RISCV/relax-debug-line.ll
@@ -0,0 +1,75 @@
+; RUN: llc -filetype=obj -mtriple=riscv32 -mattr=+relax %s -o - \
+; RUN:     | llvm-readobj -r | FileCheck -check-prefix=RELAX %s
+;
+; RELAX: .rela.debug_line {
+; RELAX: R_RISCV_ADD16
+; RELAX: R_RISCV_SUB16
+source_filename = "line.c"
+
+; Function Attrs: noinline nounwind optnone
+define i32 @init() !dbg !7 {
+entry:
+  ret i32 0, !dbg !11
+}
+
+; Function Attrs: noinline nounwind optnone
+define i32 @foo(i32 signext %value) !dbg !12 {
+entry:
+  %value.addr = alloca i32, align 4
+  store i32 %value, i32* %value.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %value.addr, metadata !15, metadata !DIExpression()), !dbg !16
+  %0 = load i32, i32* %value.addr, align 4, !dbg !17
+  ret i32 %0, !dbg !18
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+; Function Attrs: noinline nounwind optnone
+define i32 @bar() !dbg !19 {
+entry:
+  %result = alloca i32, align 4
+  %v = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %result, metadata !20, metadata !DIExpression()), !dbg !21
+  call void @llvm.dbg.declare(metadata i32* %v, metadata !22, metadata !DIExpression()), !dbg !23
+  %call = call i32 @init(), !dbg !24
+  store i32 %call, i32* %v, align 4, !dbg !23
+  %0 = load i32, i32* %v, align 4, !dbg !25
+  %call1 = call i32 @foo(i32 signext %0), !dbg !26
+  store i32 %call1, i32* %result, align 4, !dbg !27
+  %1 = load i32, i32* %result, align 4, !dbg !28
+  ret i32 %1, !dbg !29
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "line.c", directory: "./")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!7 = distinct !DISubprogram(name: "init", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: false, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DILocation(line: 3, column: 3, scope: !7)
+!12 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 6, type: !13, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!13 = !DISubroutineType(types: !14)
+!14 = !{!10, !10}
+!15 = !DILocalVariable(name: "value", arg: 1, scope: !12, file: !1, line: 6, type: !10)
+!16 = !DILocation(line: 6, column: 13, scope: !12)
+!17 = !DILocation(line: 8, column: 10, scope: !12)
+!18 = !DILocation(line: 8, column: 3, scope: !12)
+!19 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 11, type: !8, isLocal: false, isDefinition: true, scopeLine: 12, isOptimized: false, unit: !0, retainedNodes: !2)
+!20 = !DILocalVariable(name: "result", scope: !19, file: !1, line: 13, type: !10)
+!21 = !DILocation(line: 13, column: 7, scope: !19)
+!22 = !DILocalVariable(name: "v", scope: !19, file: !1, line: 14, type: !10)
+!23 = !DILocation(line: 14, column: 7, scope: !19)
+!24 = !DILocation(line: 14, column: 11, scope: !19)
+!25 = !DILocation(line: 16, column: 16, scope: !19)
+!26 = !DILocation(line: 16, column: 12, scope: !19)
+!27 = !DILocation(line: 16, column: 10, scope: !19)
+!28 = !DILocation(line: 18, column: 10, scope: !19)
+!29 = !DILocation(line: 18, column: 3, scope: !19)