This fixes a regression introduced in GCC 4.2 after which we no
longer fold (unsigned) (X /[ex] 4) * 4 to (unsigned) X.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2013-10-21 Richard Biener <rguent...@suse.de>
PR middle-end/58742
* fold-const.c (fold_binary_loc): Fold ((T) (X /[ex] C)) * C
to (T) X for sign-changing conversions (or no conversion).
* c-c++-common/fold-divmul-1.c: New testcase.
Index: gcc/fold-const.c
===================================================================
*** gcc/fold-const.c (revision 203885)
--- gcc/fold-const.c (working copy)
*************** fold_binary_loc (location_t loc,
*** 11002,11007 ****
--- 11002,11014 ----
fold_build2_loc (loc, MULT_EXPR, type,
build_int_cst (type, 2) , arg1));
+ /* ((T) (X /[ex] C)) * C cancels out if the conversion is
+ sign-changing only. */
+ if (TREE_CODE (arg1) == INTEGER_CST
+ && TREE_CODE (arg0) == EXACT_DIV_EXPR
+ && operand_equal_p (arg1, TREE_OPERAND (arg0, 1), 0))
+ return fold_convert_loc (loc, type, TREE_OPERAND (arg0, 0));
+
strict_overflow_p = false;
if (TREE_CODE (arg1) == INTEGER_CST
&& 0 != (tem = extract_muldiv (op0, arg1, code, NULL_TREE,
Index: gcc/testsuite/c-c++-common/fold-divmul-1.c
===================================================================
*** gcc/testsuite/c-c++-common/fold-divmul-1.c (revision 0)
--- gcc/testsuite/c-c++-common/fold-divmul-1.c (working copy)
***************
*** 0 ****
--- 1,11 ----
+ /* { dg-do compile } */
+ /* { dg-options "-fdump-tree-original" } */
+
+ int *
+ fx (int *b, int *e)
+ {
+ return b + (e - b);
+ }
+
+ /* { dg-final { scan-tree-dump-not "/\\\[ex\\\]" "original" } } */
+ /* { dg-final { cleanup-tree-dump "original" } } */
