[Bug rtl-optimization/116096] [15 Regression] during RTL pass: cprop_hardreg ICE: in extract_insn, at recog.cc:2848 (unrecognizable insn ashift:TI?) with -O2 -flive-range-shrinkage -fno-peephole2 -mstackrealign

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116096

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-07-25
                 CC|                            |rsandifo at gcc dot gnu.org
          Component|target                      |rtl-optimization
   Target Milestone|---                         |15.0
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is interesting.

After reload we have:
```
(insn 450 93 97 2 (set (reg:QI 2 cx [521])
        (reg:QI 38 r10 [521])) "/app/example.cpp":11:13 91 {*movqi_internal}
     (nil))
(insn 97 450 385 2 (parallel [
            (set (reg:TI 4 si [orig:337 _32 ] [337])
                (ashift:TI (const_int 1671291085 [0x639de0cd])
                    (reg:QI 2 cx [521])))
            (clobber (reg:CC 17 flags))
        ]) "/app/example.cpp":11:13 953 {ashlti3_doubleword}
     (expr_list:REG_EQUIV (mem:TI (plus:DI (reg/f:DI 19 frame)
                (const_int -80 [0xffffffffffffffb0])) [2  S16 A128])
        (expr_list:REG_EQUAL (ashift:TI (const_int 1671291085 [0x639de0cd])
                (reg:QI 38 r10 [521]))
            (nil))))
```

And then late_combine2 comes long and just updates the REG_EQUAL and tries to
re-recognize the pattern and it fails and we get:
```
(insn 450 93 97 2 (set (reg:QI 2 cx [521])
        (reg:QI 4 si [535])) "/app/example.cpp":11:13 91 {*movqi_internal}
     (nil))
(insn 97 450 385 2 (parallel [
            (set (reg:TI 4 si [orig:337 _32 ] [337])
                (ashift:TI (const_int 1671291085 [0x639de0cd])
                    (reg:QI 2 cx [521])))
            (clobber (reg:CC 17 flags))
        ]) "/app/example.cpp":11:13 -1
     (expr_list:REG_EQUIV (mem:TI (plus:DI (reg/f:DI 19 frame)
                (const_int -80 [0xffffffffffffffb0])) [2  S16 A128])
        (expr_list:REG_EQUAL (ashift:TI (const_int 1671291085 [0x639de0cd])
                (reg:QI 4 si [535]))
            (nil))))
```

Note the -1 there basically saying it was not recognized. There was no changes
to the instruction at all except updating the note:
updating notes in:
```
   97: {si:TI=0x639de0cd<<cx:QI;clobber flags:CC;}
      REG_EQUIV [frame:DI-0x50]
      REG_EQUAL 0x639de0cd<<r10:QI
updating insn 97 in-place
rescanning insn with uid = 97.
rescanning insn with uid = 450.
verify found no changes in insn with uid = 97.
```