[Bug target/53735] New: thumb1 spill failure with -Os

[aldot at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53735

             Bug #: 53735
           Summary: thumb1 spill failure with -Os
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Keywords: assemble-failure, ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: al...@gcc.gnu.org
                CC: ram...@gcc.gnu.org, rearn...@gcc.gnu.org
            Target: arm-eabi


Created attachment 27667
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27667
original source

fork() fails to assemble with -mthumb -Os, works with -O2 instead of -Os.

arm-oe-linux-uclibceabi-gcc -S fork.i -o fork.s -mthumb -Os ;# -g
-march=armv5te -mthumb-interwork -mtune=arm926ej-s -msoft-float -mlittle-endian
-feliminate-unused-debug-types -fno-tree-loop-optimize -fno-tree-dominator-opts 
fork.i: In function 'fork':
fork.i:8762:1: error: unable to find a register to spill in class 'LO_REGS'
fork.i:8762:1: error: this is the insn:
(insn 99 97 100 17 (set (reg/v:SI 4 r4 [ _v1 ])
        (plus:SI (reg/f:SI 147 [ D.8653 ])
            (const_int -1064 [0xfffffffffffffbd8])))
fork.i:8727 5 {*thumb1_addsi3}
     (nil))
fork.i:8762: confused by earlier errors, bailing out


Attached fork.i is the original, fork-reduced.i is a slightly reduced variant.
Above my original flags commented out for reference.