[Bug target/93876] New: [9 10 Regression] [SH] webkit2gtk fails to build with "error: unable to find a register to spill in class 'R0_REGS'"

[glaubitz at physik dot fu-berlin.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93876

            Bug ID: 93876
           Summary: [9 10 Regression] [SH] webkit2gtk fails to build with
                    "error: unable to find a register to spill in class
                    'R0_REGS'"
           Product: gcc
           Version: 9.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glaubitz at physik dot fu-berlin.de
                CC: gcc-bugzilla at mkarcher dot dialup.fu-berlin.de,
                    jrtc27 at jrtc27 dot com, kkojima at gcc dot gnu.org,
                    olegendo at gcc dot gnu.org
  Target Milestone: ---
            Target: sh*-*-*

Trying to build webkit2gtk on Debian sh4 with gcc-9/gcc-10 fails with:

../Source/JavaScriptCore/runtime/JSArrayBufferView.cpp: In member function
'JSC::ArrayBuffer* JSC::JSArrayBufferView::slowDownAndWasteMemory()':
../Source/JavaScriptCore/runtime/JSArrayBufferView.cpp:298:1: error: unable to
find a register to spill in class 'R0_REGS'
  298 | }
      | ^
../Source/JavaScriptCore/runtime/JSArrayBufferView.cpp:298:1: error: this is
the insn:
(insn 419 418 425 47 (parallel [
            (set (subreg:SI (reg:QI 433) 0)
                (unspec_volatile:SI [
                        (mem/v:QI (reg/f:SI 3 r3 [orig:487 _347 ] [487]) [-1 
S1 A8])
                        (reg:QI 7 r7 [425])
                        (subreg:QI (reg:SI 5 r5 [432]) 0)
                    ] UNSPECV_CMPXCHG_1))
            (set (mem/v:QI (reg/f:SI 3 r3 [orig:487 _347 ] [487]) [-1  S1 A8])
                (unspec_volatile:QI [
                        (const_int 0 [0])
                    ] UNSPECV_CMPXCHG_2))
            (set (reg:SI 147 t)
                (unspec_volatile:SI [
                        (const_int 0 [0])
                    ] UNSPECV_CMPXCHG_3))
            (clobber (scratch:SI))
            (clobber (reg:SI 0 r0))
            (clobber (reg:SI 1 r1))
        ]) "/usr/include/c++/10/bits/atomic_base.h":464:36 405
{atomic_compare_and_swapqi_soft_gusa}
     (expr_list:REG_DEAD (reg:SI 5 r5 [432])
        (expr_list:REG_DEAD (reg:QI 7 r7 [425])
            (expr_list:REG_UNUSED (reg:QI 433)
                (expr_list:REG_UNUSED (reg:SI 1 r1)
                    (expr_list:REG_UNUSED (reg:SI 0 r0)
                        (nil)))))))
../Source/JavaScriptCore/runtime/JSArrayBufferView.cpp:298: confused by earlier
errors, bailing out