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tree-ssa-uninit: suppress more spurious warnings

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* tree-ssa-uninit.c (value_sat_pred_p): This new function is a wrapper
        around is_value_included_in that knows how to handle BIT_AND_EXPR.
        (is_pred_expr_subset_of): Use the new function.  Handle more cases where
        code1 == EQ_EXPR and where code1 == BIT_AND_EXPR and thus fix some false
        positives.

testsuite/
        * gcc.dg/uninit-28-gimple.c: New test.
        * gcc.dg/uninit-29-gimple.c: New test.
        * gcc.dg/uninit-30-gimple.c: New test.
        * gcc.dg/uninit-31-gimple.c: New test.

From-SVN: r271460
This commit is contained in:
Vladislav Ivanishin 2019-05-21 10:39:05 +00:00 committed by Vladislav Ivanishin
parent 36902ed6bd
commit 0f8e84c609
7 changed files with 225 additions and 10 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2019-05-21 Vladislav Ivanishin <vlad@ispras.ru>
* tree-ssa-uninit.c (value_sat_pred_p): This new function is a wrapper
around is_value_included_in that knows how to handle BIT_AND_EXPR.
(is_pred_expr_subset_of): Use the new function. Handle more cases where
code1 == EQ_EXPR and where code1 == BIT_AND_EXPR and thus fix some false
positives.
2019-05-21 Martin Liska <mliska@suse.cz>
* config/rs6000/driver-rs6000.c (elf_platform): Do not use

7
gcc/testsuite/ChangeLog
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@ -1,3 +1,10 @@
2019-05-21 Vladislav Ivanishin <vlad@ispras.ru>
* gcc.dg/uninit-28-gimple.c: New test.
* gcc.dg/uninit-29-gimple.c: New test.
* gcc.dg/uninit-30-gimple.c: New test.
* gcc.dg/uninit-31-gimple.c: New test.
2019-05-21 Martin Liska <mliska@suse.cz>
* gcc.dg/pr90263.c: Add -O2.

47
gcc/testsuite/gcc.dg/uninit-28-gimple.c Normal file
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@ -0,0 +1,47 @@
/* { dg-do compile } */
/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
unsigned int __GIMPLE (ssa,startwith("uninit1"))
foo (unsigned int v)
{
/* Uninit warning here would be bogus, because (16 & 3) == 0 and therefore
if v == 16, the uninit value is not used (the use is properly guarded). */
unsigned int undef; /* { dg-bogus "may be used uninitialized" } */
unsigned int _2;
unsigned int _9;
unsigned int _10;
unsigned pred;
__BB(2):
if (v_4(D) != 16u)
goto __BB3;
else
goto __BB4;
/* 'undef' is defined conditionally (under 'v != 16' predicate) */
__BB(3):
undef_8 = 8u;
goto __BB4;
/* An undef value flows into a phi. */
__BB(4):
undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
pred = v_4(D) & 3u;
if (pred != 0u)
goto __BB5;
else
goto __BB6;
/* The phi value is used here (under 'v & 3' predicate). */
__BB(5):
_9 = undef_1;
goto __BB7;
__BB(6):
_10 = v_4(D);
goto __BB7;
__BB(7):
_2 = __PHI (__BB5: _9, __BB6: _10);
return _2;
}

45
gcc/testsuite/gcc.dg/uninit-29-gimple.c Normal file
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@ -0,0 +1,45 @@
/* { dg-do compile } */
/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
unsigned int __GIMPLE (ssa,startwith("uninit1"))
foo (unsigned int v)
{
unsigned int undef; /* { dg-warning "may be used uninitialized" } */
unsigned int _2;
unsigned int _9;
unsigned int _10;
unsigned pred;
__BB(2):
pred = v_4(D) & 3u;
if (pred != 0u)
goto __BB3;
else
goto __BB4;
/* 'undef' is defined conditionally (under 'v & 3' predicate) */
__BB(3):
undef_8 = 8u;
goto __BB4;
/* An undef value flows into a phi. */
__BB(4):
undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
if (v_4(D) != 16u)
goto __BB5;
else
goto __BB6;
/* The phi value is used here (under 'v != 16' predicate). */
__BB(5):
_9 = undef_1;
goto __BB7;
__BB(6):
_10 = v_4(D);
goto __BB7;
__BB(7):
_2 = __PHI (__BB5: _9, __BB6: _10);
return _2;
}

43
gcc/testsuite/gcc.dg/uninit-30-gimple.c Normal file
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@ -0,0 +1,43 @@
/* { dg-do compile } */
/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
unsigned int __GIMPLE (ssa,startwith("uninit1"))
foo (unsigned int v)
{
unsigned int undef; /* { dg-bogus "may be used uninitialized" } */
unsigned int _2;
unsigned int _9;
unsigned int _10;
__BB(2):
if (v_4(D) < 100u)
goto __BB3;
else
goto __BB4;
/* 'undef' is defined conditionally (under 'v < 100' predicate). */
__BB(3):
undef_8 = 8u;
goto __BB4;
/* An undef value flows into a phi. */
__BB(4):
undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
if (v_4(D) == 42u)
goto __BB5;
else
goto __BB6;
/* The phi value is used here (under 'v == 42' predicate). */
__BB(5):
_9 = undef_1;
goto __BB7;
__BB(6):
_10 = v_4(D);
goto __BB7;
__BB(7):
_2 = __PHI (__BB5: _9, __BB6: _10);
return _2;
}

48
gcc/testsuite/gcc.dg/uninit-31-gimple.c Normal file
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@ -0,0 +1,48 @@
/* { dg-do compile } */
/* { dg-options "-fgimple -O -Wmaybe-uninitialized" } */
unsigned int __GIMPLE (ssa,startwith("uninit1"))
foo (unsigned int v)
{
/* If v == 2, then undef is used w/o being initialized. */
unsigned int undef; /* { dg-warning "may be used uninitialized" } */
unsigned int _2;
unsigned int _9;
unsigned int _10;
unsigned int pred2;
unsigned int pred1;
__BB(2):
pred2 = v_4(D) & 5u;
if (pred2 != 0u)
goto __BB3;
else
goto __BB4;
/* 'undef' is defined conditionally (under 'v & 5' predicate). */
__BB(3):
undef_8 = 8u;
goto __BB4;
/* An undef value flows into a phi. */
__BB(4):
undef_1 = __PHI (__BB2: undef_5(D), __BB3: undef_8);
pred1 = v_4(D) & 3u;
if (pred1 != 0u)
goto __BB5;
else
goto __BB6;
/* The phi value is used here (under 'v & 3' predicate). */
__BB(5):
_9 = undef_1;
goto __BB7;
__BB(6):
_10 = v_4(D);
goto __BB7;
__BB(7):
_2 = __PHI (__BB5: _9, __BB6: _10);
return _2;
}

37
gcc/tree-ssa-uninit.c
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@ -1045,6 +1045,26 @@ is_value_included_in (tree val, tree boundary, enum tree_code cmpc)
return result;
}
/* Returns whether VAL satisfies (x CMPC BOUNDARY) predicate. CMPC can be
either one of the range comparison codes ({GE,LT,EQ,NE}_EXPR and the like),
or BIT_AND_EXPR. EXACT_P is only meaningful for the latter. It modifies the
question from whether VAL & BOUNDARY != 0 to whether VAL & BOUNDARY == VAL.
For other values of CMPC, EXACT_P is ignored. */
static bool
value_sat_pred_p (tree val, tree boundary, enum tree_code cmpc,
bool exact_p = false)
{
if (cmpc != BIT_AND_EXPR)
return is_value_included_in (val, boundary, cmpc);
wi::tree_to_wide_ref andw = wi::to_wide (val) & wi::to_wide (boundary);
if (exact_p)
return andw == wi::to_wide (val);
else
return andw.to_uhwi ();
}
/* Returns true if PRED is common among all the predicate
chains (PREDS) (and therefore can be factored out).
NUM_PRED_CHAIN is the size of array PREDS. */
@ -1471,18 +1491,15 @@ is_pred_expr_subset_of (pred_info expr1, pred_info expr2)
if (code2 == NE_EXPR && code1 == NE_EXPR)
return false;
if (code2 == NE_EXPR && code1 != BIT_AND_EXPR)
return !is_value_included_in (expr2.pred_rhs, expr1.pred_rhs, code1);
if (code2 == NE_EXPR)
return !value_sat_pred_p (expr2.pred_rhs, expr1.pred_rhs, code1);
if ((code1 == EQ_EXPR || code1 == BIT_AND_EXPR) && code2 == BIT_AND_EXPR)
return (wi::to_wide (expr1.pred_rhs)
== (wi::to_wide (expr1.pred_rhs) & wi::to_wide (expr2.pred_rhs)));
if (code1 == EQ_EXPR)
return value_sat_pred_p (expr1.pred_rhs, expr2.pred_rhs, code2);
if (code1 != code2)
return false;
if (is_value_included_in (expr1.pred_rhs, expr2.pred_rhs, code2))
return true;
if (code1 == code2)
return value_sat_pred_p (expr1.pred_rhs, expr2.pred_rhs, code2,
code1 == BIT_AND_EXPR);
return false;
}