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re PR c++/15069 (a bit test on a variable of enum type is miscompiled)

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PR middle-end/15069
	* fold-const.c (fold_single_bit_test): Only perform "(X & C) != 0"
	into "X < 0" (where C is the signbit) if X's type is a full mode.

	* g++.dg/opt/fold3.C: New test case.

From-SVN: r82490
This commit is contained in:
Roger Sayle 2004-05-31 17:01:17 +00:00 committed by Roger Sayle
parent 1027314a21
commit 1f7a8dccd4
4 changed files with 37 additions and 5 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2004-05-31 Roger Sayle <roger@eyesopen.com>
PR middle-end/15069
* fold-const.c (fold_single_bit_test): Only perform "(X & C) != 0"
into "X < 0" (where C is the signbit) if X's type is a full mode.
2004-05-31 John David Anglin <dave.anglin@nrc-cnrc.gc.ca>
* pa.md: Disable the peephole2 patterns that generate indexed

10
gcc/fold-const.c
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@ -5413,7 +5413,11 @@ fold_single_bit_test (enum tree_code code, tree arg0, tree arg1,
/* If we have (A & C) != 0 where C is the sign bit of A, convert
this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
arg00 = sign_bit_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg0, 1));
if (arg00 != NULL_TREE)
if (arg00 != NULL_TREE
/* This is only a win if casting to a signed type is cheap,
i.e. when arg00's type is not a partial mode. */
&& TYPE_PRECISION (TREE_TYPE (arg00))
== GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (arg00))))
{
tree stype = lang_hooks.types.signed_type (TREE_TYPE (arg00));
return fold (build2 (code == EQ_EXPR ? GE_EXPR : LT_EXPR,
@ -5421,10 +5425,6 @@ fold_single_bit_test (enum tree_code code, tree arg0, tree arg1,
fold_convert (stype, integer_zero_node)));
}
/* At this point, we know that arg0 is not testing the sign bit. */
if (TYPE_PRECISION (type) - 1 == bitnum)
abort ();
/* Otherwise we have (A & C) != 0 where C is a single bit,
convert that into ((A >> C2) & 1). Where C2 = log2(C).
Similarly for (A & C) == 0. */

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2004-05-31 Roger Sayle <roger@eyesopen.com>
PR middle-end/15069
* g++.dg/opt/fold3.C: New test case.
2004-05-30 Graham Stott <graham.stott@btinternet.com>
* lib/target-supports.exp (check_iconv_available): Fix fallout

21
gcc/testsuite/g++.dg/opt/fold3.C Normal file
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@ -0,0 +1,21 @@
// PR middle-end/15069
// { dg-do run }
// { dg-options "-O2" }
extern "C" void abort (void);
typedef enum {
FOUR = 4,
FIVE = 5
} direction_t;
int main ()
{
direction_t four = FOUR;
int flags = (four & 4L) ? (32L | 128L) : 0;
flags &= 32L;
if (flags == 0)
abort ();
}