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| author | Roger Sayle <roger@eyesopen.com> | 2004-05-31 17:01:17 +0000 |
|---|---|---|
| committer | Roger Sayle <sayle@gcc.gnu.org> | 2004-05-31 17:01:17 +0000 |
| commit | 1f7a8dccd4056be197e8f79fe7bbf2b8bd89c53b (patch) | |
| tree | eac927b74d933af84e28ee45cd568925d8de1411 /gcc/fold-const.c | |
| parent | 1027314a211e7b0e2b05b6bd8f179c12f784517e (diff) | |
| download | gcc-1f7a8dccd4056be197e8f79fe7bbf2b8bd89c53b.zip gcc-1f7a8dccd4056be197e8f79fe7bbf2b8bd89c53b.tar.gz gcc-1f7a8dccd4056be197e8f79fe7bbf2b8bd89c53b.tar.bz2 | |
re PR c++/15069 (a bit test on a variable of enum type is miscompiled)
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
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index d2e333e..b0d1db2 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -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. */ |