[llvm-readelf] Fix dumping of SHN_XINDEX symbols

[evgeny777]

Summary

The problem was discussed in D60555

There is no test for PRC, OS and RSV kind of symbols. Does anyone know how to generate them?
Test case uses approach suggested by @arichardson (thanks!)

[jhenderson]

There is no test for PRC, OS and RSV kind of symbols. Does anyone know how to generate them?

Use yaml2obj, with an explicit section index, but actually you don't need to test them as they are already tested by test/tools/llvm-readobj/elf-symbol-shndx.test.

test/tools/llvm-readobj/many-sections.test

1 ↗

(On Diff #194869)

Won't this generate COFF output on Windows hosts? I think you need to specify a target triple, and probably a REQUIRES: x86 or similar.

[evgeny777]

Addressed

[jhenderson]

test/tools/llvm-readobj/many-sections2.s

2

You'll need a REQUIRES: x86 line

23

As well as the CHECK-NOT, it's also probably worth checking that the values in the reserved range are printed as regular values.

[MaskRay]

test/tools/llvm-readobj/many-sections2.s

21

Delete

.macro generate_values
.endm

generate_values

You don't have to define the immediately-invoked macro.

[evgeny777]

Addressed

[evgeny777]

Addressed comments from @MaskRay

[jhenderson]

Okay, basically looks fine. Just a couple of small comments.

test/tools/llvm-readobj/many-sections2.s

2

A brief comment at the start of test describing what this test is testing might help future readers.

21

Actually, with the positive CHECKS, I don't think you need the negative ones.

26

Nit: Too many blank lines at EOF?

[evgeny777]

Addressed comments

[jhenderson]

LGTM, with nit. Might want to get @MaskRay to give thumbs up on the macro stuff, but it's probably fine.

test/tools/llvm-readobj/many-sections2.s

1

which -> whose

[rupprecht]

test/tools/llvm-readobj/many-sections2.s

8

My only concern with this patch: how long does this test take to run, specifically, how long does llvm-mc take to generate a file with this many sections? I've run into a similar issue in the past, where I wanted to create a test like this, but generating the test file from something like this took an absurd amount of time.

If it's fast, that'd be great (and if so, this patch LGTM). Maybe I'll dust off my old semi-abandoned patch and try to use this...

[evgeny777]

My only concern with this patch: how long does this test take to run, specifically, how long does llvm-mc take to generate a file with this many sections?

4 seconds in debug build (Core-i7 2600K)

test/tools/llvm-readobj/many-sections2.s

+# Tests that symbols which section index is SHN_XINDEX are displayed
+# correctly. They should not be treated as processor/OS specific or
+# reserved.
+# REQUIRES: x86-registered-target
+# RUN: llvm-mc %s -filetype=obj -triple=x86_64-pc-linux -o %t
+# RUN: llvm-readelf -s %t | FileCheck %s
+
+.irp i, 0, 1, 2, 3, 4, 5, 6,
+  .irp j, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+    .irp k, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+      .irp l, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+        .irp q, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+          .section sec_\i\j\k\l\q
+          .globl sym_\i\j\k\l\q
+           sym_\i\j\k\l\q:
+        .endr
+      .endr
+    .endr
+  .endr
+.endr
+
+# CHECK:     65278: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 65280 sym_65277
+# CHECK:     65310: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 65312 sym_65309
+# CHECK:     65342: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 65344 sym_65341

tools/llvm-readobj/ELFDumper.cpp

std::string GNUStyle<ELFT>::getSymbolSectionNdx(const ELFO *Obj,
   switch (SectionIndex) {
   case ELF::SHN_UNDEF:
     return "UND";
   case ELF::SHN_ABS:
     return "ABS";
   case ELF::SHN_COMMON:
     return "COM";
   case ELF::SHN_XINDEX:
-    SectionIndex = unwrapOrError(object::getExtendedSymbolTableIndex<ELFT>(
-        Symbol, FirstSym, this->dumper()->getShndxTable()));
-    LLVM_FALLTHROUGH;
+    return to_string(
+        format_decimal(unwrapOrError(object::getExtendedSymbolTableIndex<ELFT>(
+                           Symbol, FirstSym, this->dumper()->getShndxTable())),
+                       3));
   default:
     // Find if:
     // Processor specific
     if (SectionIndex >= ELF::SHN_LOPROC && SectionIndex <= ELF::SHN_HIPROC)
       return std::string("PRC[0x") +
              to_string(format_hex_no_prefix(SectionIndex, 4)) + "]";
     // OS specific
     if (SectionIndex >= ELF::SHN_LOOS && SectionIndex <= ELF::SHN_HIOS)