[lld] [lld][ELF] Introduce an option to keep data section prefix. (PR #148985)

[Fangrui Song via llvm-commits]

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@@ -0,0 +1,127 @@
+# REQUIRES: x86
+## -z keep-data-section-prefix separates static data sections with prefix
+## .<section>.hot, .<section>.unlikely in the absence of a SECTIONS command.
+
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64 a.s -o a.o
+
+# RUN: ld.lld a.o -o out1
+# RUN: llvm-readelf -S out1 | FileCheck --check-prefix=BASIC %s
+# RUN: ld.lld -z nokeep-text-section-prefix a.o -o out2
+# RUN: cmp out1 out2
+
+# RUN: ld.lld -z keep-data-section-prefix a.o -o out3
+# RUN: llvm-readelf -S out3 | FileCheck --check-prefix=KEEP %s
+
+## With a SECTIONS command, orphan sections are created verbatim.
+## No grouping is performed for them.
+# RUN: ld.lld -T x.lds -z keep-data-section-prefix a.o -o out4
+# RUN: llvm-readelf -S out4 | FileCheck --check-prefix=SCRIPT %s
+
+# BASIC:         [Nr] Name              Type            Address          Off    Size              
+# BASIC:         [ 1] .text       
+# BASIC-NEXT:    [ 2] .data.rel.ro      PROGBITS        00000000002021c9 0001c9 00000f
+# BASIC-NEXT:    [ 3] .bss.rel.ro       NOBITS          00000000002021d8 0001d8 000008
+# BASIC-NEXT:    [ 4] .relro_padding    NOBITS          00000000002021e0 0001d8 000e20
+# BASIC-NEXT:    [ 5] .rodata           PROGBITS        00000000002031e0 0001e0 000006
+# BASIC-NEXT:    [ 6] .data             PROGBITS        00000000002031e6 0001e6 000004
+# BASIC-NEXT:    [ 7] .bss              NOBITS          00000000002031ea 0001ea 000004
+
+# KEEP:       [Nr]  Name                    Type            Address          Off    Size
+# KEEP:       [ 1] .text
+# KEEP-NEXT:  [ 2] .data.rel.ro             PROGBITS        00000000002021c9 0001c9 000009
+# KEEP-NEXT:  [ 3] .data.rel.ro.hot         PROGBITS        00000000002021d2 0001d2 000004
+# KEEP-NEXT:  [ 4] .data.rel.ro.unlikely    PROGBITS        00000000002021d6 0001d6 000002
+# KEEP-NEXT:  [ 5] .bss.rel.ro              NOBITS          00000000002021d8 0001d8 000008
+# KEEP-NEXT:  [ 6] .relro_padding           NOBITS          00000000002021e0 0001d8 000e20
+# KEEP-NEXT:  [ 7] .rodata                  PROGBITS        00000000002031e0 0001e0 000002
+# KEEP-NEXT:  [ 8] .rodata.hot              PROGBITS        00000000002031e2 0001e2 000002
+# KEEP-NEXT:  [ 9] .rodata.unlikely         PROGBITS        00000000002031e4 0001e4 000002
+# KEEP-NEXT:  [10] .data                    PROGBITS        00000000002031e6 0001e6 000002
+# KEEP-NEXT:  [11] .data.hot                PROGBITS        00000000002031e8 0001e8 000001
+# KEEP-NEXT:  [12] .data.unlikely           PROGBITS        00000000002031e9 0001e9 000001
+# KEEP-NEXT:  [13] .bss                     NOBITS          00000000002031ea 0001ea 000002
+# KEEP-NEXT:  [14] .bss.hot                 NOBITS          00000000002031ec 0001ea 000001
+# KEEP-NEXT:  [15] .bss.unlikely            NOBITS          00000000002031ed 0001ea 000001
+
+# SCRIPT:      .text
+# SCRIPT-NEXT: .rodata.i
+# SCRIPT-NEXT: .rodata.hot.j
+# SCRIPT-NEXT: .rodata.unlikely.k
+# SCRIPT-NEXT: .rodata.split.l
+# SCRIPT-NEXT: .rodata.cst32.hot.
+# SCRIPT-NEXT: .rodata.str1.1.unlikely.
+# SCRIPT-NEXT: .data.m
+# SCRIPT-NEXT: .data.hot.n
+# SCRIPT-NEXT: .data.unlikely.o
+# SCRIPT-NEXT: .data.split.p
+# SCRIPT-NEXT: .data.rel.ro.q
+# SCRIPT-NEXT: .data.rel.ro.hot.r
+# SCRIPT-NEXT: .data.rel.ro.unlikely.s
+# SCRIPT-NEXT: .data.rel.ro.split.t
+# SCRIPT-NEXT: .bss.a
+# SCRIPT-NEXT: .bss.hot.b
+# SCRIPT-NEXT: .bss.unlikely.c
+# SCRIPT-NEXT: .bss.split.d
+# SCRIPT-NEXT: .bss.rel.ro.e
+# SCRIPT-NEXT: .bss.rel.ro.hot.f
+# SCRIPT-NEXT: .bss.rel.ro.unlikely.g
+# SCRIPT-NEXT: .bss.rel.ro.split.h
+
+#--- a.s
+.globl _start
+_start:
+  ret
+
+.section .bss.a,"aw"
+  .byte 0
+.section .bss.hot.b,"aw"
+  .byte 0
+.section .bss.unlikely.c,"aw"
+  .byte 0
+.section .bss.split.d,"aw"
+  .byte 0
+
+.section .bss.rel.ro.e, "aw"
+  .space 2
+.section .bss.rel.ro.hot.f, "aw"
+  .space 2
+.section .bss.rel.ro.unlikely.g, "aw"
+  .space 2
+.section .bss.rel.ro.split.h, "aw"
+  .space 2
+
+.section .rodata.i,"aw"
+  .byte 1
+.section .rodata.hot.j,"aw"
----------------
MaskRay wrote:

we can test `.rodata.hot.` (without `j`), for -fno-unique-section-names

https://github.com/llvm/llvm-project/pull/148985