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analyzer: fix pattern-test-2.c (PR 93291) 

Amongst the inputs to the analyzer state machines that can lead to state
transitions are conditions on CFG edges, such as a test for a pointer
being non-NULL.

These conditionals can be non-trivial to determine in the face of
optimization.  For example, at -O2:

  if (p == NULL || q == NULL)

is optimized on some targets (e.g. x86_64) to a bitwise-or:

  _1 = p_5(D) == 0B;
  _2 = q_6(D) == 0B;
  _3 = _1 | _2;
  if (_3 != 0)
    goto <bb 4>; [51.12%]
  else
    goto <bb 3>; [48.88%]

but on other targets (e.g. powerpc64le) as control flow:

  if (p_2(D) == 0B)
    goto <bb 5>; [18.09%]
  else
    goto <bb 3>; [81.91%]

  <bb 3> [local count: 879501929]:
  if (q_3(D) == 0B)
    goto <bb 5>; [30.95%]
  else
    goto <bb 4>; [69.05%]

region_model::add_any_constraints_from_ssa_def_stmt attempts to walk
SSA def chains to reconstruct the conditions that hold, so that
e.g. in the above case of bitwise-or, the state machine for
"p" can transition to the "known-null" state along the edge leading
to bb 3.

In gcc.dg/analyzer/pattern-test-2.c I attempted to write test coverage
for this, but the test fails on those targets for which the || is
expressed via control flow.

This patch rewrites the test to make explicit use of bitwise-or, and
adds coverage for bitwise-and for good measure.

gcc/testsuite/ChangeLog:
	PR analyzer/93291
	* gcc.dg/analyzer/pattern-test-2.c: Remove include of stdlib.h.
	(test_2): Rewrite to explicitly perform a bitwise-or of two
	boolean conditions.
	(test_3): New function, to test bitwise-and.
This commit is contained in:
David Malcolm 2020-01-17 11:03:15 -05:00
parent a044dfb093
commit f89e844f9c
2 changed files with 35 additions and 3 deletions
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8
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,11 @@
2020-01-27 David Malcolm <dmalcolm@redhat.com>
PR analyzer/93291
* gcc.dg/analyzer/pattern-test-2.c: Remove include of stdlib.h.
(test_2): Rewrite to explicitly perform a bitwise-or of two
boolean conditions.
(test_3): New function, to test bitwise-and.
2020-01-27 Richard Sandiford <richard.sandiford@arm.com>
PR testsuite/71727

30
gcc/testsuite/gcc.dg/analyzer/pattern-test-2.c
View File

@ -1,8 +1,6 @@
/* { dg-additional-options "-fanalyzer-checker=pattern-test -O2" } */
// TODO: run this at every optimization level
#include <stdlib.h>
extern void foo(void *);
extern void bar(void *);
@ -18,12 +16,38 @@ void test1(void *ptr)
void test_2 (void *p, void *q)
{
if (p == NULL || q == NULL) /* { dg-line cond_2 } */
_Bool tmp1 = p == 0;
_Bool tmp2 = q == 0;
_Bool tmp = tmp1 | tmp2;
/* Verify that we can detect the implied conditions on p and q here. */
if (tmp) /* { dg-line cond_2 } */
return;
foo(p);
/* { dg-warning "pattern match on 'tmp1 == 0'" "tmp1 == 0" { target *-*-* } cond_2 } */
/* { dg-warning "pattern match on 'tmp2 == 0'" "tmp2 == 0" { target *-*-* } cond_2 } */
/* { dg-warning "pattern match on '<unknown> == 0'" "<unknown> == 0" { target *-*-* } cond_2 } */
/* { dg-warning "pattern match on '<unknown> != 0'" "<unknown> != 0" { target *-*-* } cond_2 } */
/* { dg-warning "pattern match on 'p != 0'" "p != 0" { target *-*-* } cond_2 } */
/* { dg-warning "pattern match on 'q != 0'" "q != 0" { target *-*-* } cond_2 } */
}
void test_3 (void *p, void *q)
{
_Bool tmp1 = p == 0;
_Bool tmp2 = q == 0;
_Bool tmp = tmp1 & tmp2;
/* Verify that we can detect the implied conditions on p and q here. */
if (tmp) /* { dg-line cond_3 } */
return;
foo(p);
/* { dg-warning "pattern match on 'tmp1 != 0'" "tmp1 != 0" { target *-*-* } cond_3 } */
/* { dg-warning "pattern match on 'tmp2 != 0'" "tmp2 != 0" { target *-*-* } cond_3 } */
/* { dg-warning "pattern match on '<unknown> == 0'" "<unknown> == 0" { target *-*-* } cond_3 } */
/* { dg-warning "pattern match on '<unknown> != 0'" "<unknown> != 0" { target *-*-* } cond_3 } */
/* { dg-warning "pattern match on 'p == 0'" "p == 0" { target *-*-* } cond_3 } */
/* { dg-warning "pattern match on 'q == 0'" "q == 0" { target *-*-* } cond_3 } */
}