[Bug tree-optimization/122686] [16 Regression] 521.wrf_r build hang on GNR with -Ofast -march=native -flto

[haochen.jiang at intel dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122686

--- Comment #17 from Haochen Jiang <haochen.jiang at intel dot com> ---
Before the patch series:

;;   basic block 21, loop depth 1
;;    pred:       20
  _2569 = (unsigned int) _18;
  _2570 = _2569 + 1;
  _2571 = (int) _2570;
;;    succ:       22

;;   basic block 22, loop depth 2
;;    pred:       22
;;                21
  # k_699 = PHI <k_191(22), _19(21)>
  # ivtmp.894_2547 = PHI <ivtmp.894_2548(22), _2554(21)>
  # ivtmp.896_2558 = PHI <ivtmp.896_2559(22), ivtmp.904_2600(21)>
  _1794 = (float *) ivtmp.894_2547;
  _1788 = (float *) ivtmp.896_2558;
  __builtin_memcpy (_1794, _1788, _1798);
  k_191 = k_699 + 1;
  ivtmp.894_2548 = _2546 + ivtmp.894_2547;
  ivtmp.896_2559 = ivtmp.896_2558 + _2573;
  if (k_191 == _2571)
    goto <bb 23>; [11.00%]
  else
    goto <bb 22>; [89.00%]

;; Generating RTL for gimple basic block 21

;; _2571 = (int) _2570;

(insn 451 450 0 (parallel [
            (set (reg:SI 1200 [ _2571 ])
                (plus:SI (reg:SI 115 [ _18 ])
                    (const_int 1 [0x1])))
            (clobber (reg:CC 17 flags))
        ]) -1
     (nil))

;; Generating RTL for gimple basic block 22
Selected stringop expansion strategy: libcall

...


After the patch series:

;;   basic block 17, loop depth 1
;;    pred:       16
  _2616 = ivtmp.906_2548 * 4;
  ivtmp.896_2513 = _2615 + _2616;
  _2522 = (unsigned int) _18;
  _2523 = _2522 + 1;
  _2524 = (int) _2523;
;;    succ:       18

;;   basic block 18, loop depth 2
;;    pred:       18
;;                17
  # k_660 = PHI <k_191(18), _19(17)>
  # ivtmp.894_2500 = PHI <ivtmp.894_2501(18), _2507(17)>
  # ivtmp.896_2511 = PHI <ivtmp.896_2512(18), ivtmp.896_2513(17)>
  _1826 = (float *) ivtmp.894_2500;
  _256 = (float *) ivtmp.896_2511;
  __builtin_memcpy (_1826, _256, _1820);
  k_191 = k_660 + 1;
  ivtmp.894_2501 = _2499 + ivtmp.894_2500;
  ivtmp.896_2512 = ivtmp.896_2511 + _2526;
  if (k_191 == _2524)
    goto <bb 19>; [11.00%]
  else
    goto <bb 18>; [89.00%]

Then we stuck at:

;; Generating RTL for gimple basic block 17
Swap operands in stmt:
ivtmp.896_2513 = _2615 + _2616;
Cost left opnd=0, right opnd=1
 Registering value_relation (_2546 pe64 _139) (bb10) at _2546 = (unsigned long)
_139;

;; ivtmp.896_2513 = _2616 + _2615;

(insn 411 410 412 (parallel [
            (set (reg:DI 1333 [ _2616 ])
                (ashift:DI (reg:DI 1224 [ ivtmp.906 ])
                    (const_int 2 [0x2])))
            (clobber (reg:CC 17 flags))
        ]) -1
     (nil))

(insn 412 411 0 (parallel [
            (set (reg:DI 1204 [ ivtmp.896 ])
                (plus:DI (reg:DI 1333 [ _2616 ])
                    (reg:DI 1236 [ _2615 ])))
            (clobber (reg:CC 17 flags))
        ]) -1
     (nil))

;; _2524 = (int) _2523;

(insn 413 412 0 (parallel [
            (set (reg:SI 1207 [ _2524 ])
                (plus:SI (reg:SI 115 [ _18