[llvm-bugs] [Bug 44860] New: Function symbol from assembler misses lowest bit set in Thumb mode

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44860

            Bug ID: 44860
           Summary: Function symbol from assembler misses lowest bit set
                    in Thumb mode
           Product: libraries
           Version: 10.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: ARM
          Assignee: unassignedbugs at nondot.org
          Reporter: stefan at agner.ch
                CC: llvm-bugs at lists.llvm.org, peter.smith at linaro.org,
                    Ties.Stuij at arm.com

Created attachment 23113
  --> https://bugs.llvm.org/attachment.cgi?id=23113&action=edit
reproducer assembly

Using the .type directive to mark a label as a function in Thumb mode does not
get the correct symbol table entry.

        .syntax unified
        .text
        .thumb
__setup_mmu:
        it ne
        blne __setup_mmu
        .type __setup_mmu, %function // Move this line before __setup_mmu for
correct behaviour.

llvm-mc --triple=armv7a-linux-gnueabihf blne.s -filetype=obj -o blne.o
--arm-add-build-attributes
llvm-readelf --symbols blne.o

Symbol table '.symtab' contains 3 entries:
   Num:    Value  Size Type    Bind   Vis       Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT   UND
     1: 00000000     0 NOTYPE  LOCAL  DEFAULT     2 $t.0
     2: 00000000     0 FUNC    LOCAL  DEFAULT     2 __setup_mmu


This has been observed when trying to build Linux for 32-bit ARM in Thumb2
mode. When the object file gets linked, the linker inserts a blx instruction
which switches the CPU instruction set...

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