From 165ba2e9c7a6a86dbb12182486359edefba1dd9d Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Wed, 4 Jan 2017 10:07:33 +0100 Subject: [PATCH] re PR tree-optimization/71563 (Regression in GCC-7.0.0's optimizer.) PR tree-optimization/71563 * match.pd: Simplify X << Y into X if Y is known to be 0 or out of range value - has low bits known to be zero. * gcc.dg/tree-ssa/pr71563.c: New test. From-SVN: r244050 --- gcc/ChangeLog | 6 ++++++ gcc/match.pd | 15 +++++++++++++++ gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/gcc.dg/tree-ssa/pr71563.c | 23 +++++++++++++++++++++++ 4 files changed, 49 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr71563.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 06021eed5de..864c30b9ccd 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2017-01-04 Jakub Jelinek + + PR tree-optimization/71563 + * match.pd: Simplify X << Y into X if Y is known to be 0 or + out of range value - has low bits known to be zero. + 2017-01-04 Alan Modra * Makefile.in (aclocal_deps): Update and order as per aclocal.m4. diff --git a/gcc/match.pd b/gcc/match.pd index 8791e57ea21..7b968009473 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -1515,6 +1515,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (if (tem) (shiftrotate @0 { tem; })))))) +/* Simplify X << Y where Y's low width bits are 0 to X, as only valid + Y is 0. Similarly for X >> Y. */ +#if GIMPLE +(for shift (lshift rshift) + (simplify + (shift @0 SSA_NAME@1) + (if (INTEGRAL_TYPE_P (TREE_TYPE (@1))) + (with { + int width = ceil_log2 (element_precision (TREE_TYPE (@0))); + int prec = TYPE_PRECISION (TREE_TYPE (@1)); + } + (if ((get_nonzero_bits (@1) & wi::mask (width, false, prec)) == 0) + @0))))) +#endif + /* Rewrite an LROTATE_EXPR by a constant into an RROTATE_EXPR by a new constant. */ (simplify diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 4a1caa7bb04..9e7cae41419 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2017-01-04 Jakub Jelinek + + PR tree-optimization/71563 + * gcc.dg/tree-ssa/pr71563.c: New test. + 2017-01-04 Janne Blomqvist PR fortran/78534 diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr71563.c b/gcc/testsuite/gcc.dg/tree-ssa/pr71563.c new file mode 100644 index 00000000000..f01291d25dc --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr71563.c @@ -0,0 +1,23 @@ +/* PR tree-optimization/71563 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +void link_error (void); + +void +foo (int k) +{ + int t = 1 << ((1 / k) << 8); + if (t != 1) + link_error (); +} + +void +bar (int k, int l) +{ + int t = l << (k << 8); + if (t != l) + link_error (); +} + +/* { dg-final { scan-tree-dump-not "link_error" "optimized" } } */ -- 2.30.2