phiopt: Remove unnecessary checks from spaceship_replacement [PR106506]

Those 2 checks were just me trying to be extra careful, the
(phires & 1) == phires and variants it is folded to of course make only sense
for the -1/0/1/2 result spaceship, for -1/0/1 one can just use comparisons of
phires.  We only floating point spaceship if nans aren't honored, so the
2 case is ignored, and if it is, with Aldy's changes we can simplify the
2 case away from the phi but the (phires & 1) == phires stayed.  It is safe
to treat the phires comparison as phires >= 0 even then.

2022-08-12  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/106506
	* tree-ssa-phiopt.cc (spaceship_replacement): Don't punt for
	is_cast or orig_use_lhs cases if phi_bb has 3 predecessors.

	* g++.dg/opt/pr94589-2.C: New test.

diff --git a/gcc/testsuite/g++.dg/opt/pr94589-2.C b/gcc/testsuite/g++.dg/opt/pr94589-2.C
index 370deea..e9ef84b 100644 (file)
--- a/gcc/testsuite/g++.dg/opt/pr94589-2.C
+++ b/gcc/testsuite/g++.dg/opt/pr94589-2.C
@@ -1,7 +1,7 @@
 // PR tree-optimization/94589
 // { dg-do compile { target c++20 } }
 // { dg-options "-O2 -g0 -ffast-math -fdump-tree-optimized" }
-// { dg-final { scan-tree-dump-times "\[ij]_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=) \[ij]_\[0-9]+\\(D\\)" 12 "optimized" { xfail *-*-* } } }
+// { dg-final { scan-tree-dump-times "\[ij]_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=) \[ij]_\[0-9]+\\(D\\)" 12 "optimized" } }
 // { dg-final { scan-tree-dump-times "i_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=) 5\\.0" 12 "optimized" } }
 
 #include <compare>

diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index 0191b9c..d5f2ba8 100644 (file)
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -2448,8 +2448,6 @@ spaceship_replacement (basic_block cond_bb, basic_block middle_bb,
        return false;
       if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig_use_lhs))
        return false;
-      if (EDGE_COUNT (phi_bb->preds) != 4)
-       return false;
       if (!single_imm_use (orig_use_lhs, &use_p, &use_stmt))
        return false;
 
@@ -2467,8 +2465,6 @@ spaceship_replacement (basic_block cond_bb, basic_block middle_bb,
       orig_use_lhs = gimple_assign_lhs (use_stmt);
       if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig_use_lhs))
        return false;
-      if (EDGE_COUNT (phi_bb->preds) != 4)
-       return false;
       if (!single_imm_use (orig_use_lhs, &use_p, &use_stmt))
        return false;
     }