[LoongArch] Use R_LARCH_ALIGN with section symbol (#84741)

In LoongArch psABI v2.30, the R_LARCH_ALIGN requires symbol index to
support the third parameter of alignment directive. Create symbol for
each section is redundant because they have section symbol which can
also be used as symbol index. So use section symbol directly for
R_LARCH_ALIGN.

Author: MQ-mengqing

lld/ELF/InputSection.cpp

@@ -464,7 +464,11 @@ void InputSection::copyRelocations(uint8_t *buf,
         addend += sec->getFile<ELFT>()->mipsGp0;
       }
 
-      if (RelTy::IsRela)
+      if (config->emachine == EM_LOONGARCH && type == R_LARCH_ALIGN)
+        // LoongArch psABI v2.30, the R_LARCH_ALIGN requires symbol index.
+        // If it use the section symbol, the addend should not be changed.
+        p->r_addend = addend;
+      else if (RelTy::IsRela)
         p->r_addend = sym.getVA(addend) - section->getOutputSection()->addr;
       // For SHF_ALLOC sections relocated by REL, append a relocation to
       // sec->relocations so that relocateAlloc transitively called by

lld/test/ELF/loongarch-relax-align-ldr.s

@@ -0,0 +1,28 @@
+# REQUIRES: loongarch
+## Test `ld -r` not changes the addend of R_LARCH_ALIGN.
+
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 --mattr=+relax %s -o %t.64.o
+# RUN: ld.lld -r %t.64.o %t.64.o -o %t.64.r
+# RUN: llvm-objdump -dr --no-show-raw-insn %t.64.r | FileCheck %s
+
+# CHECK:      <.text>:
+# CHECK-NEXT:   break 1
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   {{0*}}04:  R_LARCH_ALIGN        .text+0x804
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   break 2
+# CHECK-NEXT:   break 0
+# CHECK-NEXT:   break 0
+# CHECK-NEXT:   break 0
+# CHECK-NEXT:   break 1
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   {{0*}}24:  R_LARCH_ALIGN        .text+0x804
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   nop
+# CHECK-NEXT:   break 2
+
+.text
+break 1
+.p2align 4, , 8
+break 2

lld/test/ELF/loongarch-relax-emit-relocs.s

@@ -25,7 +25,7 @@
 # CHECK-NEXT:     R_LARCH_PCALA_LO12 _start
 # CHECK-NEXT:     R_LARCH_RELAX *ABS*
 # CHECK-NEXT:   nop
-# CHECK-NEXT:     R_LARCH_ALIGN .Lla-relax-align0+0x4
+# CHECK-NEXT:     R_LARCH_ALIGN .text+0x4
 # CHECK-NEXT:   nop
 # CHECK-NEXT:   ret
 
@@ -37,11 +37,12 @@
 # CHECKR-NEXT:     R_LARCH_PCALA_LO12 _start
 # CHECKR-NEXT:     R_LARCH_RELAX *ABS*
 # CHECKR-NEXT:   nop
-# CHECKR-NEXT:     R_LARCH_ALIGN .Lla-relax-align0+0x4
+# CHECKR-NEXT:     R_LARCH_ALIGN .text+0x4
 # CHECKR-NEXT:   nop
 # CHECKR-NEXT:   nop
 # CHECKR-NEXT:   ret
 
+.text
 .global _start
 _start:
   la.pcrel $a0, _start

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp

@@ -226,11 +226,8 @@ bool LoongArchAsmBackend::shouldInsertFixupForCodeAlign(
       MCFixup::create(0, Dummy, MCFixupKind(LoongArch::fixup_loongarch_align));
   const MCSymbolRefExpr *MCSym = getSecToAlignSym()[Sec];
   if (MCSym == nullptr) {
-    // Create a symbol and make the value of symbol is zero.
-    MCSymbol *Sym = Ctx.createNamedTempSymbol("la-relax-align");
-    Sym->setFragment(&*Sec->getBeginSymbol()->getFragment());
-    Asm.registerSymbol(*Sym);
-    MCSym = MCSymbolRefExpr::create(Sym, Ctx);
+    // Use section symbol directly.
+    MCSym = MCSymbolRefExpr::create(Sec->getBeginSymbol(), Ctx);
     getSecToAlignSym()[Sec] = MCSym;
   }
 

llvm/test/MC/LoongArch/Relocations/relax-addsub.s

@@ -28,7 +28,7 @@
 
 # RELAX:       Relocations [
 # RELAX-NEXT:    Section ({{.*}}) .rela.text {
-# RELAX-NEXT:      0x4 R_LARCH_ALIGN {{.*}} 0x4
+# RELAX-NEXT:      0x4 R_LARCH_ALIGN .text 0x4
 # RELAX-NEXT:      0x10 R_LARCH_PCALA_HI20 .L1 0x0
 # RELAX-NEXT:      0x10 R_LARCH_RELAX - 0x0
 # RELAX-NEXT:      0x14 R_LARCH_PCALA_LO12 .L1 0x0

llvm/test/MC/LoongArch/Relocations/relax-align.s

@@ -63,17 +63,19 @@ ret
 ## Test the symbol index is different from .text.
 .section .text2, "ax"
 .p2align 4
+.p2align 4, , 4
 break 7
 
 # RELOC:            Relocations [
 # RELAX-RELOC-NEXT:   Section ({{.*}}) .rela.text {
-# RELAX-RELOC-NEXT:     0x24 R_LARCH_ALIGN .Lla-relax-align0 0x4
-# RELAX-RELOC-NEXT:     0x34 R_LARCH_ALIGN .Lla-relax-align0 0x5
-# RELAX-RELOC-NEXT:     0x50 R_LARCH_ALIGN .Lla-relax-align0 0x4
-# RELAX-RELOC-NEXT:     0x60 R_LARCH_ALIGN .Lla-relax-align0 0xB04
-# RELAX-RELOC-NEXT:     0x70 R_LARCH_ALIGN .Lla-relax-align0 0x4
+# RELAX-RELOC-NEXT:     0x24 R_LARCH_ALIGN .text 0x4
+# RELAX-RELOC-NEXT:     0x34 R_LARCH_ALIGN .text 0x5
+# RELAX-RELOC-NEXT:     0x50 R_LARCH_ALIGN .text 0x4
+# RELAX-RELOC-NEXT:     0x60 R_LARCH_ALIGN .text 0xB04
+# RELAX-RELOC-NEXT:     0x70 R_LARCH_ALIGN .text 0x4
 # RELAX-RELOC-NEXT:   }
 # RELAX-RELOC-NEXT:   Section ({{.*}}) .rela.text2 {
-# RELAX-RELOC-NEXT:     0x0 R_LARCH_ALIGN .Lla-relax-align1 0x4
+# RELAX-RELOC-NEXT:     0x0 R_LARCH_ALIGN .text2 0x4
+# RELAX-RELOC-NEXT:     0xC R_LARCH_ALIGN .text2 0x404
 # RELAX-RELOC-NEXT:   }
 # RELOC-NEXT:       ]