MIPS: Use pcrel|sdata4 for eh_frame (llvm#91291)

Gas uses encoding DW_EH_PE_absptr for PIC, and gnu ld converts it to
DW_EH_PE_sdata4|DW_EH_PE_pcrel.
LLD doesn't have this workarounding, thus complains
```
  relocation R_MIPS_32 cannot be used against local symbol; recompile with -fPIC
  relocation R_MIPS_64 cannot be used against local symbol; recompile with -fPIC
```

So, let's generates asm/obj files with `DW_EH_PE_sdata4|DW_EH_PE_pcrel`
encoding. In fact, GNU ld supports such OBJs well.

For N64, maybe we should use sdata8, while GNU ld doesn't support it
well, and in fact sdata4 is enough now. So we just ignore the `Large`
for `MCObjectFileInfo::initELFMCObjectFileInfo`. Maybe we should switch
back to sdata8 once GNU LD supports it well.

Fixes: llvm#58377.

Author: wzssyqa

lld/test/ELF/mips-eh_frame-pic.s

@@ -16,7 +16,7 @@
 # RUN: llvm-mc -filetype=obj -triple=mips64-unknown-linux --position-independent %s -o %t-pic.o
 # RUN: llvm-readobj -r %t-pic.o | FileCheck %s --check-prefixes=RELOCS,PIC64-RELOCS
 # RUN: ld.lld -shared %t-pic.o -o %t-pic.so
-# RUN: llvm-dwarfdump --eh-frame %t-pic.so | FileCheck %s --check-prefix=PIC-EH-FRAME
+# RUN: llvm-dwarfdump --eh-frame %t-pic.so | FileCheck %s --check-prefix=PIC64-EH-FRAME
 
 ## Also check MIPS32:
 # RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t-nopic32.o
@@ -31,7 +31,7 @@
 # RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux --position-independent %s -o %t-pic32.o
 # RUN: llvm-readobj -r %t-pic32.o | FileCheck %s --check-prefixes=RELOCS,PIC32-RELOCS
 # RUN: ld.lld -shared %t-pic32.o -o %t-pic32.so
-# RUN: llvm-dwarfdump --eh-frame %t-pic32.so | FileCheck %s --check-prefix=PIC-EH-FRAME
+# RUN: llvm-dwarfdump --eh-frame %t-pic32.so | FileCheck %s --check-prefix=PIC32-EH-FRAME
 
 # RELOCS:            .rel{{a?}}.eh_frame {
 # ABS32-RELOCS-NEXT:   0x1C R_MIPS_32 .text
@@ -44,7 +44,9 @@
 ##                                   ^^ fde pointer encoding: DW_EH_PE_sdata8
 # ABS32-EH-FRAME: Augmentation data: 0B
 ##                                   ^^ fde pointer encoding: DW_EH_PE_sdata4
-# PIC-EH-FRAME: Augmentation data: 1B
+# PIC32-EH-FRAME: Augmentation data: 1B
+##                                 ^^ fde pointer encoding: DW_EH_PE_pcrel | DW_EH_PE_sdata4
+# PIC64-EH-FRAME: Augmentation data: 1B
 ##                                 ^^ fde pointer encoding: DW_EH_PE_pcrel | DW_EH_PE_sdata4
 ## Note: ld.bfd converts the R_MIPS_64 relocs to DW_EH_PE_pcrel | DW_EH_PE_sdata8
 ## for N64 ABI (and DW_EH_PE_pcrel | DW_EH_PE_sdata4 for MIPS32)

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -212,13 +212,11 @@ void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
     //        identify N64 from just a triple.
     TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
                     dwarf::DW_EH_PE_sdata4;
-    // We don't support PC-relative LSDA references in GAS so we use the default
-    // DW_EH_PE_absptr for those.
 
     // FreeBSD must be explicit about the data size and using pcrel since it's
     // assembler/linker won't do the automatic conversion that the Linux tools
     // do.
-    if (TgtM.getTargetTriple().isOSFreeBSD()) {
+    if (isPositionIndependent() || TgtM.getTargetTriple().isOSFreeBSD()) {
       PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
     }

llvm/lib/MC/MCObjectFileInfo.cpp

@@ -343,7 +343,9 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
   case Triple::mips64el:
     // We cannot use DW_EH_PE_sdata8 for the large PositionIndependent case
     // since there is no R_MIPS_PC64 relocation (only a 32-bit version).
-    if (PositionIndependent && !Large)
+    // In fact DW_EH_PE_sdata4 is enough for us now, and GNU ld doesn't
+    // support pcrel|sdata8 well. Let's use sdata4 for now.
+    if (PositionIndependent)
       FDECFIEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
     else
       FDECFIEncoding = Ctx->getAsmInfo()->getCodePointerSize() == 4

llvm/test/CodeGen/Mips/ehframe-indirect.ll

@@ -17,9 +17,9 @@ define i32 @main() personality ptr @__gxx_personality_v0 {
 ; ALL: .cfi_startproc
 
 ; Linux must rely on the assembler/linker converting the encodings.
-; LINUX: .cfi_personality 128, DW.ref.__gxx_personality_v0
-; LINUX-O32: .cfi_lsda 0, $exception0
-; LINUX-NEW: .cfi_lsda 0, .Lexception0
+; LINUX: .cfi_personality 155, DW.ref.__gxx_personality_v0
+; LINUX-O32: .cfi_lsda 27, $exception0
+; LINUX-NEW: .cfi_lsda 27, .Lexception0
 
 ; FreeBSD can (and must) be more direct about the encodings it wants.
 ; FREEBSD: .cfi_personality 155, DW.ref.__gxx_personality_v0

llvm/test/DebugInfo/Mips/eh_frame.ll

@@ -17,9 +17,9 @@
 ; STATIC-DAG: R_MIPS_32 00000000 .gcc_except_table
 
 ; PIC-LABEL: Relocation section '.rel.eh_frame'
-; PIC-DAG: R_MIPS_32   00000000 DW.ref.__gxx_personality_v0
-; PIC-DAG: R_MIPS_PC32
-; PIC-DAG: R_MIPS_32   00000000 .gcc_except_table
+; PIC-DAG: R_MIPS_PC32   00000000 DW.ref.__gxx_personality_v0
+; PIC-DAG: R_MIPS_PC32   00000000 .L0
+; PIC-DAG: R_MIPS_PC32   00000000 .L0
 
 ; CHECK-READELF: DW.ref.__gxx_personality_v0
 ; CHECK-READELF-STATIC-NEXT: R_MIPS_32 00000000 .text

llvm/test/MC/Mips/eh-frame.s

@@ -33,14 +33,13 @@
 // RUN: llvm-readobj -r %t.o | FileCheck --check-prefixes=RELOCS,PIC64 %s
 // RUN: llvm-dwarfdump -eh-frame %t.o | FileCheck --check-prefixes=DWARF64,DWARF64_PIC %s
 
-/// However using the large code model forces R_MIPS_64 since there is no R_MIPS_PC64 relocation:
 // RUN: llvm-mc -filetype=obj %s -o %t.o -triple mips64-unknown-linux-gnu --position-independent --large-code-model
-// RUN: llvm-readobj -r %t.o | FileCheck --check-prefixes=RELOCS,ABS64 %s
-// RUN: llvm-dwarfdump -eh-frame %t.o | FileCheck --check-prefixes=DWARF64,DWARF64_ABS %s
+// RUN: llvm-readobj -r %t.o | FileCheck --check-prefixes=RELOCS,PIC64 %s
+// RUN: llvm-dwarfdump -eh-frame %t.o | FileCheck --check-prefixes=DWARF64,DWARF64_PIC %s
 
 // RUN: llvm-mc -filetype=obj %s -o %t.o -triple mips64el-unknown-linux-gnu --position-independent  --large-code-model
-// RUN: llvm-readobj -r %t.o | FileCheck --check-prefixes=RELOCS,ABS64 %s
-// RUN: llvm-dwarfdump -eh-frame %t.o | FileCheck --check-prefixes=DWARF64,DWARF64_ABS %s
+// RUN: llvm-readobj -r %t.o | FileCheck --check-prefixes=RELOCS,PIC64 %s
+// RUN: llvm-dwarfdump -eh-frame %t.o | FileCheck --check-prefixes=DWARF64,DWARF64_PIC %s
 
 func:
 	.cfi_startproc