Change how we handle section symbols on ELF.

On ELF every section can have a corresponding section symbol. When in
an assembly file we have

.quad .text

the '.text' refers to that symbol.

The way we used to handle them is to leave .text an undefined symbol
until the very end when the object writer would map them to the
actual section symbol.

The problem with that is that anything before the end would see an
undefined symbol. This could result in bad diagnostics
(test/MC/AArch64/label-arithmetic-diags-elf.s), or incorrect results
when using the asm streamer (est/MC/Mips/expansion-jal-sym-pic.s).

Fixing this will also allow using the section symbol earlier for
setting sh_link of SHF_METADATA sections.

This patch includes a few hacks to avoid changing our behaviour when
handling conflicts between section symbols and other symbols. I
reported pr31850 to track that.

llvm-svn: 293936

1 files changed, 13 insertions, 15 deletions

diff --git a/llvm/lib/MC/MCObjectFileInfo.cpp b/llvm/lib/MC/MCObjectFileInfo.cpp
index 9238520cc59..5e81026ad40 100644
--- a/llvm/lib/MC/MCObjectFileInfo.cpp
+++ b/llvm/lib/MC/MCObjectFileInfo.cpp
@@ -506,10 +506,9 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T) {
   COFFDebugTypesSection = nullptr;
 
   // Debug Info Sections.
-  DwarfAbbrevSection = Ctx->getELFSection(".debug_abbrev", ELF::SHT_PROGBITS, 0,
-                                          "section_abbrev");
-  DwarfInfoSection =
-      Ctx->getELFSection(".debug_info", ELF::SHT_PROGBITS, 0, "section_info");
+  DwarfAbbrevSection =
+      Ctx->getELFSection(".debug_abbrev", ELF::SHT_PROGBITS, 0);
+  DwarfInfoSection = Ctx->getELFSection(".debug_info", ELF::SHT_PROGBITS, 0);
   DwarfLineSection = Ctx->getELFSection(".debug_line", ELF::SHT_PROGBITS, 0);
   DwarfFrameSection = Ctx->getELFSection(".debug_frame", ELF::SHT_PROGBITS, 0);
   DwarfPubNamesSection =
@@ -527,21 +526,21 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T) {
   DwarfARangesSection =
       Ctx->getELFSection(".debug_aranges", ELF::SHT_PROGBITS, 0);
   DwarfRangesSection =
-      Ctx->getELFSection(".debug_ranges", ELF::SHT_PROGBITS, 0, "debug_range");
-  DwarfMacinfoSection = Ctx->getELFSection(".debug_macinfo", ELF::SHT_PROGBITS,
-                                           0, "debug_macinfo");
+      Ctx->getELFSection(".debug_ranges", ELF::SHT_PROGBITS, 0);
+  DwarfMacinfoSection =
+      Ctx->getELFSection(".debug_macinfo", ELF::SHT_PROGBITS, 0);
 
   // DWARF5 Experimental Debug Info
 
   // Accelerator Tables
   DwarfAccelNamesSection =
-      Ctx->getELFSection(".apple_names", ELF::SHT_PROGBITS, 0, "names_begin");
+      Ctx->getELFSection(".apple_names", ELF::SHT_PROGBITS, 0);
   DwarfAccelObjCSection =
-      Ctx->getELFSection(".apple_objc", ELF::SHT_PROGBITS, 0, "objc_begin");
-  DwarfAccelNamespaceSection = Ctx->getELFSection(
-      ".apple_namespaces", ELF::SHT_PROGBITS, 0, "namespac_begin");
+      Ctx->getELFSection(".apple_objc", ELF::SHT_PROGBITS, 0);
+  DwarfAccelNamespaceSection =
+      Ctx->getELFSection(".apple_namespaces", ELF::SHT_PROGBITS, 0);
   DwarfAccelTypesSection =
-      Ctx->getELFSection(".apple_types", ELF::SHT_PROGBITS, 0, "types_begin");
+      Ctx->getELFSection(".apple_types", ELF::SHT_PROGBITS, 0);
 
   // Fission Sections
   DwarfInfoDWOSection =
@@ -556,11 +555,10 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T) {
   DwarfLineDWOSection =
       Ctx->getELFSection(".debug_line.dwo", ELF::SHT_PROGBITS, 0);
   DwarfLocDWOSection =
-      Ctx->getELFSection(".debug_loc.dwo", ELF::SHT_PROGBITS, 0, "skel_loc");
+      Ctx->getELFSection(".debug_loc.dwo", ELF::SHT_PROGBITS, 0);
   DwarfStrOffDWOSection =
       Ctx->getELFSection(".debug_str_offsets.dwo", ELF::SHT_PROGBITS, 0);
-  DwarfAddrSection =
-      Ctx->getELFSection(".debug_addr", ELF::SHT_PROGBITS, 0, "addr_sec");
+  DwarfAddrSection = Ctx->getELFSection(".debug_addr", ELF::SHT_PROGBITS, 0);
 
   // DWP Sections
   DwarfCUIndexSection =