| Message ID | DM2PR0701MB1018B6682277C9F319FC55208E840@DM2PR0701MB1018.namprd07.prod.outlook.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jul 21, 2015 at 11:16 AM, Hurugalawadi, Naveen <Naveen.Hurugalawadi@caviumnetworks.com> wrote: > Hi, > >>> handle exact_div differently, like fold-const.c does. >>> Then expressing ~1 with the result expression is really excessive - you >>> should simply build this with @1 - 1 if @1 is a power of two. (*) > Thanks for the review and comments. > > Please find attached the modified patch as per your comments. > > Please review the same and let me know if any further modifications are required. > > Regression Tested on X86_64. We already have +(simplify + (mult (exact_div @0 INTEGET_CST@1) @1) + @0) as /* (X /[ex] A) * A -> X. */ (simplify (mult (convert? (exact_div @0 @1)) @1) /* Look through a sign-changing conversion. */ (convert @0)) as before the comment applies to your second pattern. +(simplify + (mult (trunc_div @0 integer_pow2p@1) @1) + (bit_and @0 (negate @1))) This doesn't work for signed types at least. -1 / 2 * 2 == 0, not -2. Your previous patch correctly restricted this to unsigned types. Thanks, Richard. > Thanks, > Naveen > > gcc/testsuite/ChangeLog: > > 2015-07-21 Naveen H.S <Naveen.Hurugalawadi@caviumnetworks.com> > > PR middle-end/25530 > * gcc.dg/pr25530.c: New test. > > gcc/ChangeLog: > > 2015-07-21 Naveen H.S <Naveen.Hurugalawadi@caviumnetworks.com> > > PR middle-end/25530 > * match.pd (mult (exact_div @0 INTEGET_CST@1) @1) : New simplifier. > (mult (trunc_div @0 integer_pow2p@1) @1) : New simplifier.
--- a/gcc/match.pd +++ b/gcc/match.pd @@ -280,6 +280,15 @@ along with GCC; see the file COPYING3. If not see && integer_pow2p (@2) && tree_int_cst_sgn (@2) > 0) (bit_and @0 (convert (minus @1 { build_int_cst (TREE_TYPE (@1), 1); })))))) +/* Simplify (unsigned t / 2) * 2 -> unsigned t & ~1. */ +(simplify + (mult (exact_div @0 INTEGET_CST@1) @1) + @0) + +(simplify + (mult (trunc_div @0 integer_pow2p@1) @1) + (bit_and @0 (negate @1))) + /* X % Y is smaller than Y. */ (for cmp (lt ge) (simplify new file mode 100644 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr25530.c @@ -0,0 +1,14 @@ +new file mode 100644 +--- /dev/null ++++ b/gcc/testsuite/gcc.dg/pr25530.c +@@ -0,0 +1,10 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +int +f (unsigned t) +{ + return (t / 2) * 2; +} + +/* { dg-final { scan-tree-dump "\& -2" "optimized" } } */