[Bug rtl-optimization/80723] New: [8 Regression] FAIL gcc.target/i386/cadd.c scan assembler sbb

["ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80723

            Bug ID: 80723
           Summary: [8 Regression] FAIL gcc.target/i386/cadd.c scan
                    assembler sbb
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ubizjak at gmail dot com
  Target Milestone: ---

This is a recent failure on 32bit x86 target, where if-conversion is not
performed for some reason (but it is for 32bit target).

gcc -O2 -march=k8

64 bit target:
==============

_.243r.ce1:

;; Function q (q, funcdef_no=0, decl_uid=1821, cgraph_uid=0, symbol_order=1)

0 registers.

9 basic blocks, 10 edges.

    4: NOTE_INSN_BASIC_BLOCK 2
    2: NOTE_INSN_FUNCTION_BEG
    6: r89:DI=`t'
    3: r88:SI=0

   16: L16:
    8: NOTE_INSN_BASIC_BLOCK 3
    9: flags:CCZ=cmp([r89:DI],0)
   10: pc={(flags:CCZ==0)?L13:pc}
      REG_DEAD flags:CCZ
      REG_BR_PROB 5000

   11: NOTE_INSN_BASIC_BLOCK 4
   12: {r88:SI=r88:SI+0x1;clobber flags:CC;}
      REG_UNUSED flags:CC

   13: L13:
   14: NOTE_INSN_BASIC_BLOCK 5
   15: {r89:DI=r89:DI+0x4;clobber flags:CC;}
      REG_UNUSED flags:CC
   17: flags:CCZ=cmp(r89:DI,const(`t'+0x28))
   18: pc={(flags:CCZ!=0)?L16:pc}
      REG_DEAD flags:CCZ
      REG_BR_PROB 9000

   19: NOTE_INSN_BASIC_BLOCK 6
   20: flags:CCZ=cmp(r88:SI,0x6)
      REG_DEAD r88:SI
   21: pc={(flags:CCZ==0)?L27:pc}
      REG_DEAD flags:CCZ
      REG_BR_PROB 9996

   22: NOTE_INSN_BASIC_BLOCK 7
   23: call [`abort'] argc:0
      REG_CALL_DECL `abort'
      REG_NORETURN 0
      REG_EH_REGION 0

   27: L27:
   28: NOTE_INSN_BASIC_BLOCK 8






try_optimize_cfg iteration 1

;; 2 loops found
;;
;; Loop 0
;;  header 0, latch 1
;;  depth 0, outer -1
;;  nodes: 0 1 2 3 4 5 6 7 8
;;
;; Loop 1
;;  header 3, latch 5
;;  depth 1, outer 0
;;  nodes: 3 5 4
;; 2 succs { 3 }
;; 3 succs { 4 5 }
;; 4 succs { 5 }
;; 5 succs { 3 6 }
;; 6 succs { 7 8 }
;; 7 succs { }
;; 8 succs { 1 }
starting the processing of deferred insns
ending the processing of deferred insns
df_analyze called

IF-THEN-JOIN block found, pass 1, test 3, then 4, join 5
scanning new insn with uid = 30.
scanning new insn with uid = 31.
if-conversion succeeded through noce_try_addcc
Removing jump 10.
deleting insn with uid = 10.
deleting insn with uid = 12.
deleting block 4
Conversion succeeded on pass 1.

IF-CASE-2 found, start 6, else 8

32 bit target:
==============

;; Function q (q, funcdef_no=0, decl_uid=1760, cgraph_uid=0, symbol_order=1)

0 registers.

9 basic blocks, 10 edges.

    5: NOTE_INSN_BASIC_BLOCK 2
    2: NOTE_INSN_FUNCTION_BEG
    3: r90:SI=0
    4: r88:SI=0

   16: L16:
    7: NOTE_INSN_BASIC_BLOCK 3
    9: flags:CCZ=cmp([r90:SI*0x4+`t'],0)
   10: pc={(flags:CCZ==0)?L13:pc}
      REG_DEAD flags:CCZ
      REG_BR_PROB 5000

   11: NOTE_INSN_BASIC_BLOCK 4
   12: {r88:SI=r88:SI+0x1;clobber flags:CC;}
      REG_UNUSED flags:CC

   13: L13:
   14: NOTE_INSN_BASIC_BLOCK 5
   15: {r90:SI=r90:SI+0x1;clobber flags:CC;}
      REG_UNUSED flags:CC
   17: flags:CCZ=cmp(r90:SI,0xa)
   18: pc={(flags:CCZ!=0)?L16:pc}
      REG_DEAD flags:CCZ
      REG_BR_PROB 9000

   19: NOTE_INSN_BASIC_BLOCK 6
   20: flags:CCZ=cmp(r88:SI,0x6)
      REG_DEAD r88:SI
   21: pc={(flags:CCZ==0)?L27:pc}
      REG_DEAD flags:CCZ
      REG_BR_PROB 9996

   22: NOTE_INSN_BASIC_BLOCK 7
   23: call [`abort'] argc:0
      REG_CALL_DECL `abort'
      REG_NORETURN 0
      REG_EH_REGION 0

   27: L27:
   28: NOTE_INSN_BASIC_BLOCK 8





try_optimize_cfg iteration 1

;; 2 loops found
;;
;; Loop 0
;;  header 0, latch 1
;;  depth 0, outer -1
;;  nodes: 0 1 2 3 4 5 6 7 8
;;
;; Loop 1
;;  header 3, latch 5
;;  depth 1, outer 0
;;  nodes: 3 5 4
;; 2 succs { 3 }
;; 3 succs { 4 5 }
;; 4 succs { 5 }
;; 5 succs { 3 6 }
;; 6 succs { 7 8 }
;; 7 succs { }
;; 8 succs { 1 }
starting the processing of deferred insns
ending the processing of deferred insns
df_analyze called

IF-THEN-JOIN block found, pass 1, test 3, then 4, join 5

IF-CASE-2 found, start 6, else 8


AFAICS, the starting sequence is almost equal (32bit target has more complex
memory access, but it shouldn't matter here), so it should also be converted
through noce_try_addcc on 32bit targets.