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New testcase for uninit

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The following adds a testcase that illustrates a defect in
compute_control_dep_chain and its attempt to identify loop
exits as special to continue walking post-dominators but failing
to do so for following post-dominators.  On trunk there is now
simple_control_dep_chain saving the day, avoiding the false
positive but with GCC 12 we get a bogus diagnostic.

	* gcc.dg/uninit-pred-11.c: New testcase.
This commit is contained in:
Richard Biener 2022-08-26 12:56:30 +02:00
parent d6621a2f31
commit fc1b5707fa
1 changed files with 27 additions and 0 deletions
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27
gcc/testsuite/gcc.dg/uninit-pred-11.c Normal file
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/* { dg-do compile } */
/* { dg-options "-O -Wmaybe-uninitialized" } */
extern unsigned bar (void);
extern void quux (void);
int z;
unsigned foo (unsigned v, int y)
{
unsigned u;
if (v != 1)
u = bar ();
// Prevent the "dom" pass from changing the CFG layout based on the inference
// 'if (v != 1) is false then (v != 2) is true'. (Now it would have to
// duplicate the loop in order to do so, which is deemed expensive.)
for (int i = 0; i < 10; i++)
quux ();
// This variation from uninit-25.c causes compute_control_dep_chain
// to run into a defect but simple_control_dep_chain saves us here
if (y)
z = 1;
if (v != 1)
return u; /* { dg-bogus "may be used uninitialized" } */
return 0;
}