[Bug gas/25108] New: gas will not assemble legal thumb-1 ADR if -march=armv4t is thrown

[rcwhaley at iu dot edu]

https://sourceware.org/bugzilla/show_bug.cgi?id=25108

            Bug ID: 25108
           Summary: gas will not assemble legal  thumb-1 ADR if
                    -march=armv4t is thrown
           Product: binutils
           Version: 2.33
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gas
          Assignee: unassigned at sourceware dot org
          Reporter: rcwhaley at iu dot edu
  Target Milestone: ---

I believe that this is due to an improper patch for this bug report:
   https://lists.gnu.org/archive/html/bug-binutils/2015-06/msg00074.html

Basically, if you tell gas to give you the original thumb-1 ISA using -thumb
-march=armv4t, it will refuse to assemble an ADR instruction using the
preferred label form.  For instance, this code will assemble without specifying
armv4t, but will die with it:
****
.text
.thumb
.syntax unified
.globl mrgSort
mrgSort:
   adr r0, mrgSort
bx lr
******

Note that the above instruction is valid for all thumb ISAs according to the
ARM documentation, but gas refuses to assemble it unless you specify armv7,
which lets in a huge number of instructions that are incompatible with thumb-1.

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