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| author | Jakub Jelinek <jakub@redhat.com> | 2017-10-06 09:11:25 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@gcc.gnu.org> | 2017-10-06 09:11:25 +0200 |
| commit | 4e34b338f703d72e1d4a90116e9d2c6aa0a3d5d8 (patch) | |
| tree | 1edd646c5ff05278d73442bec96be0300188aeaf /gcc/c-family | |
| parent | bd8d431f44377efe110b02163d693e60421acdeb (diff) | |
| download | gcc-4e34b338f703d72e1d4a90116e9d2c6aa0a3d5d8.zip gcc-4e34b338f703d72e1d4a90116e9d2c6aa0a3d5d8.tar.gz gcc-4e34b338f703d72e1d4a90116e9d2c6aa0a3d5d8.tar.bz2 | |
re PR c/82437 (false-positive -Wtautological-compare warning with -std=gnu89)
PR c/82437
* c-warn.c (warn_tautological_bitwise_comparison): Instead of
using to_widest use wide_int with the larger of the two precisions.
* c-c++-common/Wtautological-compare-6.c: New test.
From-SVN: r253476
Diffstat (limited to 'gcc/c-family')
| -rw-r--r-- | gcc/c-family/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/c-family/c-warn.c | 18 |
2 files changed, 19 insertions, 5 deletions
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog index 639fd22..f70b6f8 100644 --- a/gcc/c-family/ChangeLog +++ b/gcc/c-family/ChangeLog @@ -1,3 +1,9 @@ +2017-10-06 Jakub Jelinek <jakub@redhat.com> + + PR c/82437 + * c-warn.c (warn_tautological_bitwise_comparison): Instead of + using to_widest use wide_int with the larger of the two precisions. + 2017-10-05 Bernd Edlinger <bernd.edlinger@hotmail.de> * c-pretty-print.c (pp_c_parameter_type_list): Print ... for variadic diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c index f86de10..2eb4cf5 100644 --- a/gcc/c-family/c-warn.c +++ b/gcc/c-family/c-warn.c @@ -356,16 +356,24 @@ warn_tautological_bitwise_comparison (location_t loc, tree_code code, return; /* Note that the two operands are from before the usual integer - conversions, so their types might not be the same. */ - widest_int res; + conversions, so their types might not be the same. + Use the larger of the two precisions and ignore bits outside + of that. */ + int prec = MAX (TYPE_PRECISION (TREE_TYPE (cst)), + TYPE_PRECISION (TREE_TYPE (bitopcst))); + + wide_int bitopcstw = wide_int::from (bitopcst, prec, UNSIGNED); + wide_int cstw = wide_int::from (cst, prec, UNSIGNED); + + wide_int res; if (TREE_CODE (bitop) == BIT_AND_EXPR) - res = wi::to_widest (bitopcst) & wi::to_widest (cst); + res = bitopcstw & cstw; else - res = wi::to_widest (bitopcst) | wi::to_widest (cst); + res = bitopcstw | cstw; /* For BIT_AND only warn if (CST2 & CST1) != CST1, and for BIT_OR only if (CST2 | CST1) != CST1. */ - if (res == wi::to_widest (cst)) + if (res == cstw) return; if (code == EQ_EXPR) |