commit 14cfa0dcdc4a476bdbeff66cb0297ce68a1b8ad5
author David Blaikie <dblaikie@gmail.com> Sat Oct 20 09:16:49 2018 +0000
committer David Blaikie <dblaikie@gmail.com> Sat Oct 20 09:16:49 2018 +0000
tree d91dcaecb1c3f2414cdc5d1079e9b009e73aeeb6
parent 4a5b01ddd7dd12f9a5826741e57104e8bf54748b

DebugInfo: Use base address specifiers more aggressively

Using a base address specifier even for a single-element range is a size
win for object files (7 words versus 8 words - more significant savings
if the debug info is compressed (since it's 3 words of uncompressable
reloc + 4 compressable words compared to 6 uncompressable reloc + 2
compressable words) - does trade off executable size increase though.

llvm-svn: 344841

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 3d842e7..2f14f54 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2163,7 +2163,7 @@
     // or optnone where there may be holes in a single CU's section
     // contributions.
     auto *Base = CUBase;
-    if (!Base && P.second.size() > 1 &&
+    if (!Base && (P.second.size() > 1 || DwarfVersion < 5) &&
         (UseDwarfRangesBaseAddressSpecifier || DwarfVersion >= 5)) {
       BaseIsSet = true;
       // FIXME/use care: This may not be a useful base address if it's not

llvm/test/DebugInfo/X86/range_reloc.ll

diff --git a/llvm/test/DebugInfo/X86/range_reloc.ll b/llvm/test/DebugInfo/X86/range_reloc.ll
index bcb11cc..5c40cf3 100644
--- a/llvm/test/DebugInfo/X86/range_reloc.ll
+++ b/llvm/test/DebugInfo/X86/range_reloc.ll
@@ -16,8 +16,21 @@
 ; smaller (the growth of debug_ranges itself would be more significant).
 
 ; COMMON: {{^.Ldebug_ranges0}}
-; COMMON-NEXT:   .quad   .Lfunc_begin0
-; COMMON-NEXT:   .quad   .Lfunc_end0
+; 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
@@ -25,15 +38,13 @@
 ; BASE-NEXT:   .quad   .Lfunc_begin3-.Lfunc_begin1
 ; BASE-NEXT:   .quad   .Lfunc_end3-.Lfunc_begin1
 ; BASE-NEXT:   .quad   -1
-; BASE-NEXT:   .quad   0
-; NOBASE-NEXT:   .quad   .Lfunc_begin1
-; NOBASE-NEXT:   .quad   .Lfunc_end1
-; NOBASE-NEXT:   .quad   .Lfunc_begin3
-; NOBASE-NEXT:   .quad   .Lfunc_end3
-; COMMON-NEXT:   .quad   .Lfunc_begin4
-; COMMON-NEXT:   .quad   .Lfunc_end4
-; COMMON-NEXT:   .quad   .Lfunc_begin5
-; COMMON-NEXT:   .quad   .Lfunc_end5
+; 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