[Bug target/115188] New: [14/15 regression] invalid Thumb assembly for atomic store in loop on ARMv6

[Bug target/115188] New: [14/15 regression] invalid Thumb assembly for atomic store in loop on ARMv6

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115188

            Bug ID: 115188
           Summary: [14/15 regression] invalid Thumb assembly for atomic
                    store in loop on ARMv6
           Product: gcc
           Version: 14.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ebotcazou at gcc dot gnu.org
  Target Milestone: ---

This apparently comes from the fix for PR target/111235: the following code:

int data[4];

void init (unsigned int lb, unsigned int hb)
{
  for (unsigned int i = lb; i < hb; i++)
    __atomic_store_4 (&data[i], 0, __ATOMIC_RELAXED);
}

yields invalid assembly when compiled with -mthumb -mcpu=cortex-m0 -O2:

t.s: Assembler messages:
t.s:35: Warning: missing operand; zero assumed
t.s:35: Error: cannot use register index with PC-relative addressing -- `str
r1,r0!'

[Bug target/115188] [14/15 regression] invalid Thumb assembly for atomic store in loop on ARMv6

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115188

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |arm
           Keywords|                            |wrong-code
   Target Milestone|---                         |14.2

[Bug target/115188] [14/15 regression] invalid Thumb assembly for atomic store in loop on ARMv6

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115188

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=115153,
                   |                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=111235
             Target|arm                         |arm-eabi

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
At first I thought it was the same failure as PR 115153 but it is different.

[Bug target/115188] [14/15 regression] invalid Thumb assembly for atomic store in loop on ARMv6

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115188

Wilco <wilco at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |wilco at gcc dot gnu.org
   Last reconfirmed|                            |2024-05-23

--- Comment #2 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> At first I thought it was the same failure as PR 115153 but it is different.

It's similar in that 'm' apparently allows LDMIA/STMIA with writeback in
Thumb-1. The correct constraint is 'Uw'.