[ELF] Sort IRELATIVE by offset

Improve the test gnu-ifunc-nonpreemptible.s to check IRELATIVE offsets.
Ensure that IRELATIVE offsets are ordered to improve locality.

lld/ELF/SyntheticSections.cpp

@@ -1666,7 +1666,7 @@ void RelocationBaseSection::computeRels() {
   parallelForEach(relocs,
                   [symTab](DynamicReloc &rel) { rel.computeRaw(symTab); });
 
-  auto irelative = std::partition(
+  auto irelative = std::stable_partition(
       relocs.begin() + numRelativeRelocs, relocs.end(),
       [t = target->iRelativeRel](auto &r) { return r.type != t; });
 

lld/test/ELF/gnu-ifunc-nonpreemptible.s

@@ -1,62 +1,75 @@
 # REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
-# RUN: ld.lld %t.o -o %t
-# RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn %t | FileCheck %s --check-prefix=DISASM
-# RUN: llvm-readelf -r -s %t | FileCheck %s
+# RUN: rm -rf %t && split-file %s %t && cd %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64 a.s -o a.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64 b.s -o b.o
+# RUN: ld.lld -shared -soname=b.so b.o -o b.so
 
-# RUN: ld.lld --export-dynamic %t.o -o %t
-# RUN: llvm-readelf -r -s %t | FileCheck %s
+# RUN: ld.lld a.o -o a
+# RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn a | FileCheck %s --check-prefix=DISASM
+# RUN: llvm-readelf -r -s a | FileCheck %s
 
-# CHECK:      Relocation section '.rela.dyn' at offset {{.*}} contains 2 entries:
+# CHECK:      Relocation section '.rela.dyn' at offset {{.*}} contains 3 entries:
 # CHECK-NEXT:     Type
-# CHECK-NEXT: R_X86_64_IRELATIVE
-# CHECK-NEXT: R_X86_64_IRELATIVE
+# CHECK-NEXT: {{0*}}[[#%x,O:]] [[#%x,]] R_X86_64_IRELATIVE  [[#%x,QUX:]]
+# CHECK-NEXT: {{0*}}[[#O+8]]   [[#%x,]] R_X86_64_IRELATIVE
+# CHECK-NEXT: {{0*}}[[#O+16]]  [[#%x,]] R_X86_64_IRELATIVE
 
-# CHECK:      0 NOTYPE  LOCAL  HIDDEN     [[#]] __rela_iplt_start
-# CHECK-NEXT: 0 NOTYPE  LOCAL  HIDDEN     [[#]] __rela_iplt_end
+# CHECK:                      0 NOTYPE  LOCAL  HIDDEN     [[#]] __rela_iplt_start
+# CHECK-NEXT:                 0 NOTYPE  LOCAL  HIDDEN     [[#]] __rela_iplt_end
+# CHECK-NEXT: {{0*}}[[#QUX]]  0 IFUNC   GLOBAL DEFAULT    [[#]] qux
 
-# RUN: ld.lld -pie %t.o -o %t1
-# RUN: llvm-readelf -s %t1 | FileCheck %s --check-prefix=PIC
-# RUN: ld.lld -shared %t.o -o %t2
-# RUN: llvm-readelf -s %t2 | FileCheck %s --check-prefix=PIC
+# RUN: ld.lld -pie a.o b.so -o a1
+# RUN: llvm-readelf -rs a1 | FileCheck %s --check-prefixes=PIC,PIE
+# RUN: ld.lld -shared a.o b.so -o a2
+# RUN: llvm-readelf -rs a2 | FileCheck %s --check-prefix=PIC
+
+# PIC:                                 R_X86_64_GLOB_DAT      0000000000000000 ext + 0
+# PIC-NEXT: {{0*}}[[#%x,O:]]  [[#%x,]] R_X86_64_64            0000000000000000 __rela_iplt_start + 0
+# PIC-NEXT: {{0*}}[[#O+8]]    [[#%x,]] R_X86_64_64            0000000000000000 __rela_iplt_end + 0
+# PIE-NEXT: {{0*}}[[#O+16]]   [[#%x,]] R_X86_64_IRELATIVE
+# PIE-NEXT: {{0*}}[[#O+24]]   [[#%x,]] R_X86_64_IRELATIVE
+# PIE-NEXT: {{0*}}[[#O+32]]   [[#%x,]] R_X86_64_IRELATIVE
 
 # PIC:        0 NOTYPE  WEAK   DEFAULT    UND __rela_iplt_start
 # PIC-NEXT:   0 NOTYPE  WEAK   DEFAULT    UND __rela_iplt_end
 
 # DISASM: Disassembly of section .text:
 # DISASM-EMPTY:
-# DISASM-NEXT: <foo>:
+# DISASM-NEXT: <qux>:
+# DISASM:      <foo>:
 # DISASM:      <bar>:
 # DISASM:      <unused>:
 # DISASM:      <_start>:
 # DISASM-NEXT:   callq 0x[[#%x,foo:]]
 # DISASM-NEXT:   callq 0x[[#%x,bar:]]
+# DISASM-NEXT:   callq 0x[[#%x,qux:]]
 # DISASM-EMPTY:
 # DISASM-NEXT: Disassembly of section .iplt:
 # DISASM-EMPTY:
 # DISASM-NEXT: <.iplt>:
-# DISASM-NEXT:  [[#foo]]: jmpq *{{.*}}(%rip)
+# DISASM-NEXT:  [[#qux]]: jmpq *{{.*}}(%rip)
 # DISASM-NEXT:            pushq $0
 # DISASM-NEXT:            jmp 0x0
-# DISASM-NEXT:  [[#bar]]: jmpq *{{.*}}(%rip)
+# DISASM-NEXT:  [[#foo]]: jmpq *{{.*}}(%rip)
 # DISASM-NEXT:            pushq $1
 # DISASM-NEXT:            jmp 0x0
+# DISASM-NEXT:  [[#bar]]: jmpq *{{.*}}(%rip)
+# DISASM-NEXT:            pushq $2
+# DISASM-NEXT:            jmp 0x0
 
-.text
+#--- a.s
+.globl qux, foo, bar
+.type qux, @gnu_indirect_function
 .type foo STT_GNU_IFUNC
-.globl foo
-foo:
- ret
-
 .type bar STT_GNU_IFUNC
-.globl bar
-bar:
- ret
+qux: ret
+foo: ret
+bar: ret
 
 .type unused, @gnu_indirect_function
 .globl unused
-unused:
-  ret
+.weak ext
+unused: mov ext@gotpcrel(%rip), %rax
 
 .weak __rela_iplt_start
 .weak __rela_iplt_end
@@ -65,7 +78,13 @@ unused:
 _start:
  call foo
  call bar
+ call qux
 
 .data
   .quad __rela_iplt_start
   .quad __rela_iplt_end
+
+#--- b.s
+.globl ext
+ext:
+  ret