DebugInfo: Add a CU metadata attribute for use of DWARF ranges base address specifiers

Summary:
Ranges base address specifiers can save a lot of object size in
relocation records especially in optimized builds.

For an optimized self-host build of Clang with split DWARF and debug
info compression in object files, but uncompressed debug info in the
executable, this change produces about 18% smaller object files and 6%
larger executable.

While it would've been nice to turn this on by default, gold's 32 bit
gdb-index support crashes on this input & I don't think there's any
perfect heuristic to implement solely in LLVM that would suffice - so
we'll need a flag one way or another (also possible people might want to
aggressively optimized for executable size that contains debug info
(even with compression this would still come at some cost to executable
size)) - so let's plumb it through.

Differential Revision: https://reviews.llvm.org/D54242

llvm-svn: 346788

1 files changed, 103 insertions, 67 deletions

diff --git a/llvm/test/DebugInfo/X86/range_reloc.ll b/llvm/test/DebugInfo/X86/range_reloc.ll
index 5c40cf31944..37ed4a76fd8 100644
--- a/llvm/test/DebugInfo/X86/range_reloc.ll
+++ b/llvm/test/DebugInfo/X86/range_reloc.ll
@@ -1,5 +1,4 @@
-; RUN: llc -filetype=asm -mtriple=x86_64-pc-linux-gnu %s -o - -use-dwarf-ranges-base-address-specifier | FileCheck --check-prefix=COMMON --check-prefix=BASE %s
-; RUN: llc -filetype=asm -mtriple=x86_64-pc-linux-gnu %s -o - | FileCheck --check-prefix=COMMON --check-prefix=NOBASE %s
+; RUN: llc -filetype=asm -mtriple=x86_64-pc-linux-gnu %s -o - | FileCheck %s
 ; RUN: llc -filetype=asm -mtriple=x86_64-pc-linux-gnu %s -o - -dwarf-version 5 | FileCheck --check-prefix=DWARF5 %s
 
 ; Group ranges in a range list that apply to the same section and use a base
@@ -15,38 +14,51 @@
 ; in the linked executable. Without compression in the objects, the win would be
 ; smaller (the growth of debug_ranges itself would be more significant).
 
-; COMMON: {{^.Ldebug_ranges0}}
-; NOBASE-NEXT:   .quad   .Lfunc_begin0
-; NOBASE-NEXT:   .quad   .Lfunc_end0
-; NOBASE-NEXT:   .quad   .Lfunc_begin1
-; NOBASE-NEXT:   .quad   .Lfunc_end1
-; NOBASE-NEXT:   .quad   .Lfunc_begin3
-; NOBASE-NEXT:   .quad   .Lfunc_end3
-; NOBASE-NEXT:   .quad   .Lfunc_begin4
-; NOBASE-NEXT:   .quad   .Lfunc_end4
-; NOBASE-NEXT:   .quad   .Lfunc_begin5
-; NOBASE-NEXT:   .quad   .Lfunc_end5
-
-; BASE-NEXT:   .quad   -1
-; BASE-NEXT:   .quad   .Lfunc_begin0
-; BASE-NEXT:   .quad   .Lfunc_begin0-.Lfunc_begin0
-; BASE-NEXT:   .quad   .Lfunc_end0-.Lfunc_begin0
-; BASE-NEXT:   .quad   -1
-; BASE-NEXT:   .quad   .Lfunc_begin1
-; BASE-NEXT:   .quad   .Lfunc_begin1-.Lfunc_begin1
-; BASE-NEXT:   .quad   .Lfunc_end1-.Lfunc_begin1
-; BASE-NEXT:   .quad   .Lfunc_begin3-.Lfunc_begin1
-; BASE-NEXT:   .quad   .Lfunc_end3-.Lfunc_begin1
-; BASE-NEXT:   .quad   -1
-; BASE-NEXT:   .quad   .Lfunc_begin4
-; BASE-NEXT:   .quad   .Lfunc_begin4-.Lfunc_begin4
-; BASE-NEXT:   .quad   .Lfunc_end4-.Lfunc_begin4
-; BASE-NEXT:   .quad   -1
-; BASE-NEXT:   .quad   .Lfunc_begin5
-; BASE-NEXT:   .quad   .Lfunc_begin5-.Lfunc_begin5
-; BASE-NEXT:   .quad   .Lfunc_end5-.Lfunc_begin5
-; COMMON-NEXT:   .quad   0
-; COMMON-NEXT:   .quad   0
+; This is a merged module containing two CUs, one that uses range base address
+; specifiers and exercises different cases there, and another that does not
+
+; ranges.cpp
+; Single range entry
+; __attribute__((section("a"))) void f1() {}
+; Single address with two ranges due to the whole caused by f3
+; __attribute__((section("b"))) void f2() {}
+; __attribute__((section("b"))) __attribute__((nodebug)) void f3() {}
+; __attribute__((section("b"))) void f4() {}
+; Reset the base address & emit a couple more single range entries
+; __attribute__((section("c"))) void f5() {}
+; __attribute__((section("d"))) void f6() {}
+; ranges_no_base.cpp:
+; Include enough complexity to cause ranges to be emitted, so it can be checked
+; that those ranges don't use base address specifiers
+; __attribute__((section("e"))) void f7() {}
+; __attribute__((section("f"))) void f8() {}
+
+; CHECK: {{^.Ldebug_ranges0}}
+; CHECK-NEXT:   .quad   -1
+; CHECK-NEXT:   .quad   .Lfunc_begin0
+; CHECK-NEXT:   .quad   .Lfunc_begin0-.Lfunc_begin0
+; CHECK-NEXT:   .quad   .Lfunc_end0-.Lfunc_begin0
+; CHECK-NEXT:   .quad   -1
+; CHECK-NEXT:   .quad   .Lfunc_begin1
+; CHECK-NEXT:   .quad   .Lfunc_begin1-.Lfunc_begin1
+; CHECK-NEXT:   .quad   .Lfunc_end1-.Lfunc_begin1
+; CHECK-NEXT:   .quad   .Lfunc_begin3-.Lfunc_begin1
+; CHECK-NEXT:   .quad   .Lfunc_end3-.Lfunc_begin1
+; CHECK-NEXT:   .quad   -1
+; CHECK-NEXT:   .quad   .Lfunc_begin4
+; CHECK-NEXT:   .quad   .Lfunc_begin4-.Lfunc_begin4
+; CHECK-NEXT:   .quad   .Lfunc_end4-.Lfunc_begin4
+; CHECK-NEXT:   .quad   -1
+; CHECK-NEXT:   .quad   .Lfunc_begin5
+; CHECK-NEXT:   .quad   .Lfunc_begin5-.Lfunc_begin5
+; CHECK-NEXT:   .quad   .Lfunc_end5-.Lfunc_begin5
+; CHECK-NEXT:   .quad   0
+; CHECK-NEXT:   .quad   0
+; CHECK-NEXT: {{^.Ldebug_ranges1}}
+; CHECK-NEXT:   .quad   .Lfunc_begin6
+; CHECK-NEXT:   .quad   .Lfunc_end6
+; CHECK-NEXT:   .quad   .Lfunc_begin7
+; CHECK-NEXT:   .quad   .Lfunc_end7
 
 ; DWARF5: {{^.Ldebug_ranges0}}
 ; DWARF5-NEXT:                                      # DW_RLE_startx_length
@@ -67,65 +79,89 @@
 ; DWARF5-NEXT: .byte 4                              #   start index
 ; DWARF5-NEXT: .uleb128 .Lfunc_end5-.Lfunc_begin5   #   length
 ; DWARF5-NEXT:                                      # DW_RLE_end_of_list
+; DWARF5-NEXT: {{^.Ldebug_ranges1}}
+; DWARF5-NEXT:                                      # DW_RLE_startx_length
+; DWARF5-NEXT: .byte 5                              #   start index
+; DWARF5-NEXT: .uleb128 .Lfunc_end6-.Lfunc_begin6   #   length
+; DWARF5-NEXT:                                      # DW_RLE_startx_length
+; DWARF5-NEXT: .byte 6                              #   start index
+; DWARF5-NEXT: .uleb128 .Lfunc_end7-.Lfunc_begin7   #   length
+; DWARF5-NEXT:                                      # DW_RLE_end_of_list
 
 ; Function Attrs: noinline nounwind optnone uwtable
-define void @_Z2f1v() #0 section "a" !dbg !7 {
+define dso_local void @_Z2f1v() section "a" !dbg !9 {
 entry:
-  ret void, !dbg !10
+  ret void, !dbg !12
 }
 
 ; Function Attrs: noinline nounwind optnone uwtable
-define void @_Z2f2v() #0 section "b" !dbg !11 {
+define dso_local void @_Z2f2v() section "b" !dbg !13 {
 entry:
-  ret void, !dbg !12
+  ret void, !dbg !14
 }
 
 ; Function Attrs: noinline nounwind optnone uwtable
-define void @_Z2f3v() #0 section "b" {
+define dso_local void @_Z2f3v() section "b" {
 entry:
   ret void
 }
 
 ; Function Attrs: noinline nounwind optnone uwtable
-define void @_Z2f4v() #0 section "b" !dbg !13 {
+define dso_local void @_Z2f4v() section "b" !dbg !15 {
 entry:
-  ret void, !dbg !14
+  ret void, !dbg !16
 }
 
 ; Function Attrs: noinline nounwind optnone uwtable
-define void @_Z2f5v() #0 section "e" !dbg !15 {
+define dso_local void @_Z2f5v() section "c" !dbg !17 {
 entry:
-  ret void, !dbg !16
+  ret void, !dbg !18
 }
 
 ; Function Attrs: noinline nounwind optnone uwtable
-define void @_Z2f6v() #0 section "f" !dbg !17 {
+define dso_local void @_Z2f6v() section "d" !dbg !19 {
 entry:
-  ret void, !dbg !18
+  ret void, !dbg !20
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local void @_Z2f7v() section "e" !dbg !21 {
+entry:
+  ret void, !dbg !22
 }
 
-attributes #0 = { noinline nounwind optnone uwtable "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" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local void @_Z2f8v() section "f" !dbg !23 {
+entry:
+  ret void, !dbg !24
+}
 
-!llvm.dbg.cu = !{!0}
-!llvm.module.flags = !{!3, !4, !5}
-!llvm.ident = !{!6}
+!llvm.dbg.cu = !{!0, !3}
+!llvm.ident = !{!5, !5}
+!llvm.module.flags = !{!6, !7, !8}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 (trunk 309523) (llvm/trunk 309526)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
-!1 = !DIFile(filename: "funcs.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (trunk 346343) (llvm/trunk 346350)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None, debugBaseAddress: true)
+!1 = !DIFile(filename: "ranges.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
 !2 = !{}
-!3 = !{i32 2, !"Dwarf Version", i32 4}
-!4 = !{i32 2, !"Debug Info Version", i32 3}
-!5 = !{i32 1, !"wchar_size", i32 4}
-!6 = !{!"clang version 6.0.0 (trunk 309523) (llvm/trunk 309526)"}
-!7 = distinct !DISubprogram(name: "f1", linkageName: "_Z2f1v", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
-!8 = !DISubroutineType(types: !9)
-!9 = !{null}
-!10 = !DILocation(line: 1, column: 42, scope: !7)
-!11 = distinct !DISubprogram(name: "f2", linkageName: "_Z2f2v", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
-!12 = !DILocation(line: 2, column: 42, scope: !11)
-!13 = distinct !DISubprogram(name: "f4", linkageName: "_Z2f4v", scope: !1, file: !1, line: 4, type: !8, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
-!14 = !DILocation(line: 4, column: 42, scope: !13)
-!15 = distinct !DISubprogram(name: "f5", linkageName: "_Z2f5v", scope: !1, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
-!16 = !DILocation(line: 5, column: 42, scope: !15)
-!17 = distinct !DISubprogram(name: "f6", linkageName: "_Z2f6v", scope: !1, file: !1, line: 6, type: !8, isLocal: false, isDefinition: true, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
-!18 = !DILocation(line: 6, column: 42, scope: !17)
+!3 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !4, producer: "clang version 8.0.0 (trunk 346343) (llvm/trunk 346350)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!4 = !DIFile(filename: "ranges_no_base.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!5 = !{!"clang version 8.0.0 (trunk 346343) (llvm/trunk 346350)"}
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 4}
+!9 = distinct !DISubprogram(name: "f1", linkageName: "_Z2f1v", scope: !1, file: !1, line: 1, type: !10, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!10 = !DISubroutineType(types: !11)
+!11 = !{null}
+!12 = !DILocation(line: 1, column: 42, scope: !9)
+!13 = distinct !DISubprogram(name: "f2", linkageName: "_Z2f2v", scope: !1, file: !1, line: 2, type: !10, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!14 = !DILocation(line: 2, column: 42, scope: !13)
+!15 = distinct !DISubprogram(name: "f4", linkageName: "_Z2f4v", scope: !1, file: !1, line: 4, type: !10, isLocal: false, isDefinition: true, scopeLine: 4, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!16 = !DILocation(line: 4, column: 42, scope: !15)
+!17 = distinct !DISubprogram(name: "f5", linkageName: "_Z2f5v", scope: !1, file: !1, line: 5, type: !10, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!18 = !DILocation(line: 5, column: 42, scope: !17)
+!19 = distinct !DISubprogram(name: "f6", linkageName: "_Z2f6v", scope: !1, file: !1, line: 6, type: !10, isLocal: false, isDefinition: true, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, retainedNodes: !2)
+!20 = !DILocation(line: 6, column: 42, scope: !19)
+!21 = distinct !DISubprogram(name: "f7", linkageName: "_Z2f7v", scope: !4, file: !4, line: 1, type: !10, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !3, retainedNodes: !2)
+!22 = !DILocation(line: 1, column: 42, scope: !21)
+!23 = distinct !DISubprogram(name: "f8", linkageName: "_Z2f8v", scope: !4, file: !4, line: 2, type: !10, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !3, retainedNodes: !2)
+!24 = !DILocation(line: 2, column: 42, scope: !23)