[PATCH] D27041: [ELF] - Disable emiting multiple output sections when merging is disabled.

[George Rimar via llvm-commits]

grimar created this revision.
grimar added reviewers: ruiu, rafael.
grimar added subscribers: llvm-commits, grimar, emaste, evgeny777.

When -O0 is specified, we do not do section merging.
Though before this patch several sections were generated instead
of single, what is useless I think.

This is important for current testing of FreeBSD bootstrap.
Particulaty for EFI loader. Since allows to get closer to output of
gnu linkers when needed.


https://reviews.llvm.org/D27041

Files:
  ELF/LinkerScript.cpp
  test/ELF/no-merge.s


Index: test/ELF/no-merge.s
===================================================================
--- test/ELF/no-merge.s
+++ test/ELF/no-merge.s
@@ -0,0 +1,25 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "SECTIONS { .data : {*(.data.*)} }" > %t0.script
+# RUN: ld.lld %t.o -o %t0.out --script %t0.script
+# RUN: llvm-objdump -s %t0.out | FileCheck %s --check-prefix=OPT
+# OPT:      Contents of section .data:
+# OPT-NEXT:   0000 01
+# OPT-NEXT: Contents of section .data:
+# OPT-NEXT:   0001 6100
+# OPT-NEXT: Contents of section .data:
+# OPT-NEXT:   0003 03
+
+# RUN: ld.lld -O0 %t.o -o %t1.out --script %t0.script
+# RUN: llvm-objdump -s %t1.out | FileCheck %s --check-prefix=NOOPT
+# NOOPT:      Contents of section .data:
+# NOOPT-NEXT:   0000 01610003
+
+.section .data.aw,"aw", at progbits
+.byte 1
+
+.section .data.ams,"aMS", at progbits,1
+.asciz "a"
+
+.section .data.am,"aM", at progbits,1
+.byte 3
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -277,6 +277,11 @@
   typedef typename ELFT::uint uintX_t;
   uintX_t Flags = C->Flags & (SHF_MERGE | SHF_STRINGS);
 
+  // We do not do merge of sections in case when optimization is disabled,
+  // drop the flags in that case to stop produce multiple output sections.
+  if (Config->Optimize == 0)
+    Flags = 0;
+
   uintX_t Alignment = 0;
   if (isa<MergeInputSection<ELFT>>(C))
     Alignment = std::max<uintX_t>(C->Alignment, C->Entsize);


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