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[Bug target/70120] New: [aarch64] -mno-pc-relative-literal-loads -g causes Assembler messages: Error: unaligned opcodes detected in executable segment


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70120

            Bug ID: 70120
           Summary: [aarch64] -mno-pc-relative-literal-loads -g causes
                    Assembler messages: Error: unaligned opcodes detected
                    in executable segment
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: assemble-failure
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
            Target: aarch64-unknown-linux-gnu

Created attachment 37885
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37885&action=edit
reduced testcase

Compiler output:
$ aarch64-unknown-linux-gnu-gcc -Og -fschedule-insns
-mno-pc-relative-literal-loads -g testcase.c
/tmp/ccGjqX1U.s: Assembler messages:
/tmp/ccGjqX1U.s: Error: unaligned opcodes detected in executable segment

$ aarch64-unknown-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-aarch64/bin/aarch64-unknown-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-234020-checking-yes-rtl-df-nographite-aarch64/bin/../libexec/gcc/aarch64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-checking=yes,rtl,df --without-cloog --without-ppl --without-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=aarch64-unknown-linux-gnu
--with-ld=/usr/bin/aarch64-unknown-linux-gnu-ld
--with-as=/usr/bin/aarch64-unknown-linux-gnu-as
--with-sysroot=/usr/aarch64-unknown-linux-gnu --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-234020-checking-yes-rtl-df-nographite-aarch64
Thread model: posix
gcc version 6.0.0 20160307 (experimental) (GCC) 

There are two ways to fix the assembly.
1) align the data:
@@ -279,6 +279,7 @@
        .align  1
 .LC3:
        .hword  0
+       .hword  0
 .Letext0:
        .section        .debug_info,"",@progbits
 .Ldebug_info0:

2) place the data in .rodata:
@@ -276,9 +276,11 @@
        .hword  0
        .hword  0
        .hword  0
+       .section .rodata
        .align  1
 .LC3:
        .hword  0
+       .text
 .Letext0:
        .section        .debug_info,"",@progbits
 .Ldebug_info0:

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