[Bug middle-end/95021] [10/11 Regression] Bogus -Wclobbered warning

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95021

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
271r.ce2 dump has

;; bb 0 artificial_defs: { d2(0){ }d5(1){ }d8(2){ }d9(6){ }d17(7){ }d34(16){
}d44(19){ }d47(20){ }d50(21){ }d53(22){ }d66(28){ }d69(29){ }d72(30){ }}
;; bb 0 artificial_uses: { }
;; lr  in        85
;; lr  use
;; lr  def       0 [ax] 1 [dx] 2 [cx] 6 [bp] 7 [sp] 16 [argp] 19 [frame] 20
[xmm0] 21 [xmm1] 22 [xmm2] 28 [mm0] 29 [mm1] 30 [mm2]
;; live  in     
;; live  gen     0 [ax] 1 [dx] 2 [cx] 6 [bp] 7 [sp] 16 [argp] 19 [frame] 20
[xmm0] 21 [xmm1] 22 [xmm2] 28 [mm0] 29 [mm1] 30 [mm2]
;; live  kill
;; lr  out       6 [bp] 7 [sp] 16 [argp] 19 [frame] 85
;; live  out     6 [bp] 7 [sp] 16 [argp] 19 [frame]
...
;; bb 2 artificial_defs: { }
;; bb 2 artificial_uses: { u0(6){ }u1(7){ }u2(16){ }u3(19){ }}
;; lr  in        6 [bp] 7 [sp] 16 [argp] 19 [frame] 85
;; lr  use       6 [bp] 7 [sp] 16 [argp] 19 [frame]
;; lr  def       0 [ax] 1 [dx] 2 [cx] 7 [sp] 8 [st] 9 [st(1)] 10 [st(2)] 11
[st(3)] 12 [st(4)] 13 [st(5)] 14 [st(6)] 15 [st(7)] 17 [flags] 18 [fpsr] 20
[xmm0] 21 [xmm1] 22 [xmm2] 23 [xmm3] 24 [xmm4] 25 [xmm5] 26 [xmm6] 27 [xmm7] 28
[mm0] 29 [mm1] 30 [mm2] 31 [mm3] 32 [mm4] 33 [mm5] 34 [mm6] 35 [mm7] 36 [r8] 37
[r9] 38 [r10] 39 [r11] 40 [r12] 41 [r13] 42 [r14] 43 [r15] 44 [xmm8] 45 [xmm9]
46 [xmm10] 47 [xmm11] 48 [xmm12] 49 [xmm13] 50 [xmm14] 51 [xmm15] 52 [xmm16] 53
[xmm17] 54 [xmm18] 55 [xmm19] 56 [xmm20] 57 [xmm21] 58 [xmm22] 59 [xmm23] 60
[xmm24] 61 [xmm25] 62 [xmm26] 63 [xmm27] 64 [xmm28] 65 [xmm29] 66 [xmm30] 67
[xmm31] 68 [k0] 69 [k1] 70 [k2] 71 [k3] 72 [k4] 73 [k5] 74 [k6] 75 [k7] 88
;; live  in      6 [bp] 7 [sp] 16 [argp] 19 [frame]
;; live  gen     0 [ax] 7 [sp] 17 [flags] 88
;; live  kill    17 [flags]
;; lr  out       6 [bp] 7 [sp] 16 [argp] 19 [frame] 85
;; live  out     6 [bp] 7 [sp] 16 [argp] 19 [frame]

Since IRA has

 /* DF_LIVE can't be used in the register allocator, too many other
     parts of the compiler depend on using the "classic" liveness
     interpretation of the DF_LR problem.  See PR38711.
     Remove the problem, so that we don't spend time updating it in
     any of the df_analyze() calls during IRA/LRA.  */
  if (optimize > 1) 
    df_remove_problem (df_live);
  gcc_checking_assert (df_live == NULL);

setjmp_vars_warning uses DF_LR info and gets the wrong result.

Why is DF_LR info so way off? Reg 85 isn't live at function entry
nor at BB 2 exit.