CCP should be able to optimize the following to return 0; in a single pass invocation. int foo (int i) { int j = i; int k = 0; int l = j + k; int m = l - j; return m; }
I have a patch teaching CCP to perform copy propagation in its lattice.
Author: rguenth Date: Tue Apr 21 12:52:43 2015 New Revision: 222267 URL: https://gcc.gnu.org/viewcvs?rev=222267&root=gcc&view=rev Log: 2015-04-21 Richard Biener <rguenther@suse.de> PR tree-optimization/65650 * tree-ssa-ccp.c (valid_lattice_transition): Allow lattice transitions involving copies. (set_lattice_value): Adjust for copy lattice state. (ccp_lattice_meet): Do not merge UNDEFINED and a copy to the copy if that doesn't dominate the merge point. (bit_value_unop): Adjust what we treat as varying mask. (bit_value_binop): Likewise. (bit_value_assume_aligned): Likewise. (evaluate_stmt): When we simplified to a SSA name record a copy instead of dropping to varying. (visit_assignment): Simplify. * gimple-match.h (gimple_simplify): Add another callback. * gimple-fold.c (fold_stmt_1): Adjust caller. (gimple_fold_stmt_to_constant_1): Likewise - pass valueize for the 2nd callback. * gimple-match-head.c (gimple_simplify): Add a callback that is used to valueize the stmt operands and use it that way. * gcc.dg/tree-ssa/ssa-ccp-37.c: New testcase. * gcc.dg/tree-ssa/forwprop-11.c: Adjust. * gcc.dg/tree-ssa/ssa-fre-3.c: Likewise. * gcc.dg/tree-ssa/ssa-fre-4.c: Likewise. * gcc.dg/tree-ssa/ssa-fre-5.c: Likewise. * gcc.dg/tree-ssa/ssa-fre-32.c: Likewise. Added: trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-37.c Modified: trunk/gcc/ChangeLog trunk/gcc/gimple-fold.c trunk/gcc/gimple-match-head.c trunk/gcc/gimple-match.h trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.dg/tree-ssa/forwprop-11.c trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-3.c trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-32.c trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-4.c trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-5.c trunk/gcc/tree-ssa-ccp.c
Fixed.