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References: <bug-33099-91@http.gcc.gnu.org/bugzilla/>
Subject: [Bug tree-optimization/33099] [4.2 Regression] Scalar evolutions confusing VRP with pointer values that wrap around
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From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
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------- Comment #6 from pinskia at gcc dot gnu dot org  2007-08-17 20:42 -------
The IR is the same but scev did something different:
Visiting statement:
p_10 = i.0_9 - 1B;

(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = p_10)
(get_scalar_evolution 
  (scalar = p_10)
  (scalar_evolution = ))
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i.0_9)
(get_scalar_evolution 
  (scalar = i.0_9)
  (scalar_evolution = {0B, +, 1B}_1))
(set_scalar_evolution 
  (scalar = i.0_9)
  (scalar_evolution = {0B, +, 1B}_1))
)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = 1B)
(get_scalar_evolution 
  (scalar = 1B)
  (scalar_evolution = 1B))
)
(set_scalar_evolution 
  (scalar = p_10)
  (scalar_evolution = {4294967295B, +, 1B}_1))
)
(instantiate_parameters 
  (loop_nb = 1)
  (chrec = {4294967295B, +, 1B}_1)
  (res = {4294967295B, +, 1B}_1))
Found new range for p_10: VARYING

vs (in 4.2):
 Visiting statement:
i.0_4 = (char *) i_23;

(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i.0_4)
(get_scalar_evolution 
  (scalar = i.0_4)
  (scalar_evolution = ))
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i_23)
(get_scalar_evolution 
  (scalar = i_23)
  (scalar_evolution = {0, +, 1}_1))
(set_scalar_evolution 
  (scalar = i_23)
  (scalar_evolution = {0, +, 1}_1))
)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i_1)
(get_scalar_evolution 
  (scalar = i_1)
  (scalar_evolution = {0, +, 1}_1))
(set_scalar_evolution 
  (scalar = i_1)
  (scalar_evolution = {0, +, 1}_1))
)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = N.1_3)
(get_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = ))
(set_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = N.1_3)
(get_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
(set_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = N.1_3)
(get_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
(set_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
)
(instantiate_parameters 
  (loop_nb = 1)
  (chrec = N.1_3)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = N.1_3)
(get_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
(set_scalar_evolution 
  (scalar = N.1_3)
  (scalar_evolution = N.1_3))
)
  (res = scev_not_known))
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i_8)
(get_scalar_evolution 
  (scalar = i_8)
  (scalar_evolution = ))
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i_25)
(get_scalar_evolution 
  (scalar = i_25)
  (scalar_evolution = {0, +, 1}_1))
(set_scalar_evolution 
  (scalar = i_25)
  (scalar_evolution = {0, +, 1}_1))
)
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = 1)
(get_scalar_evolution 
  (scalar = 1)
  (scalar_evolution = 1))
)
(set_scalar_evolution 
  (scalar = i_8)
  (scalar_evolution = {1, +, 1}_1))
)
(instantiate_parameters 
  (loop_nb = 1)
  (chrec = {1, +, 1}_1)
  (res = {1, +, 1}_1))
Induction variable (int) 1 + 1 * iteration does not wrap in statement i_8 =
i_25 + 1 in loop 1.
Statement i_8 = i_25 + 1 is executed at most 2147483646 (bounded by 2147483646)
+ 1 times in loop 1.
(analyze_scalar_evolution 
  (loop_nb = 1)
  (scalar = i_25)
(get_scalar_evolution 
  (scalar = i_25)
  (scalar_evolution = {0, +, 1}_1))
(set_scalar_evolution 
  (scalar = i_25)
  (scalar_evolution = {0, +, 1}_1))
)
(instantiate_parameters 
  (loop_nb = 1)
  (chrec = {0, +, 1}_1)
  (res = {0, +, 1}_1))
Induction variable (int) 0 + 1 * iteration does not wrap in statement i_25 =
ASSERT_EXPR <i_1, i_1 < N.1_3> in loop 1.
Statement i_25 = ASSERT_EXPR <i_1, i_1 < N.1_3> is executed at most 2147483647
(bounded by 2147483647) + 1 times in loop 1.
(set_scalar_evolution 
  (scalar = i.0_4)
  (scalar_evolution = {0B, +, 1B}_1))
)
(instantiate_parameters 
  (loop_nb = 1)
  (chrec = {0B, +, 1B}_1)
  (res = {0B, +, 1B}_1))
Found new range for i.0_4: [0B, -1B]


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33099