This fixes an integer overflow warning that ultimatively happens because of TREE_OVERFLOW propagating through transforms and the existing guard against this,
375 if (TREE_OVERFLOW_P (ret) 376 && !TREE_OVERFLOW_P (op0) 377 && !TREE_OVERFLOW_P (op1)) 378 overflow_warning (EXPR_LOC_OR_LOC (expr, input_location, being insufficient. Rather than trying to use sth like walk_tree to exhaustively walk operands (with the possibility of introducing quadraticness when folding larger expressions recursively) the following amends the above with an ad-hoc test for a binary op0 with a possibly constant op1. Bootstrapped and tested on x86_64-unknown-linux-gnu, OK? Thanks, Richard. 2020-05-19 Richard Biener <rguent...@suse.de> PR c/95141 c/ * c-fold.c (c_fully_fold_internal): Enhance guard on overflow_warning. * gcc.dg/pr95141.c: New testcase. --- gcc/c/c-fold.c | 1 + gcc/testsuite/gcc.dg/pr95141.c | 8 ++++++++ 2 files changed, 9 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/pr95141.c diff --git a/gcc/c/c-fold.c b/gcc/c/c-fold.c index 63becfeaf2c..bd21d247051 100644 --- a/gcc/c/c-fold.c +++ b/gcc/c/c-fold.c @@ -374,6 +374,7 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands, ret = fold (expr); if (TREE_OVERFLOW_P (ret) && !TREE_OVERFLOW_P (op0) + && !(BINARY_CLASS_P (op0) && TREE_OVERFLOW_P (TREE_OPERAND (op0, 1))) && !TREE_OVERFLOW_P (op1)) overflow_warning (EXPR_LOC_OR_LOC (expr, input_location), ret, expr); if (code == LSHIFT_EXPR diff --git a/gcc/testsuite/gcc.dg/pr95141.c b/gcc/testsuite/gcc.dg/pr95141.c new file mode 100644 index 00000000000..b6cbba2f908 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr95141.c @@ -0,0 +1,8 @@ +/* { dg-do compile } */ + +#include <stdint.h> + +uint64_t test(uint8_t IA1) +{ + return (uint8_t)(IA1 & 158) & 1UL; /* { dg-bogus "integer overflow" } */ +} -- 2.25.1