The PR indicates a very specific issue with regard to SSA coalescing
failures because there's a pre IV increment loop exit test. While
IVOPTs created the desired IL we later simplify the exit test into
the undesirable form again. The following fixes this up during RTL
expansion where we try to improve coalescing of IVs. That seems
easier that trying to avoid the simplification with some weird
heuristics (it could also have been written this way).
Bootstrapped and tested on x86_64-unknown-linux-gnu.
OK for trunk?
Thanks,
Richard.
PR tree-optimization/86270
* tree-outof-ssa.cc (insert_backedge_copies): Pattern
match a single conflict in a loop condition and adjust
that avoiding the conflict if possible.
* gcc.target/i386/pr86270.c: Adjust to check for no reg-reg
copies as well.
---
gcc/testsuite/gcc.target/i386/pr86270.c | 3 ++
gcc/tree-outof-ssa.cc | 49 ++++++++++++++++++++++---
2 files changed, 47 insertions(+), 5 deletions(-)
diff --git a/gcc/testsuite/gcc.target/i386/pr86270.c
b/gcc/testsuite/gcc.target/i386/pr86270.c
index 68562446fa4..89b9aeb317a 100644
--- a/gcc/testsuite/gcc.target/i386/pr86270.c
+++ b/gcc/testsuite/gcc.target/i386/pr86270.c
@@ -13,3 +13,6 @@ test ()
/* Check we do not split the backedge but keep nice loop form. */
/* { dg-final { scan-assembler-times "L\[0-9\]+:" 2 } } */
+/* Check we do not end up with reg-reg moves from a pre-increment IV
+ exit test. */
+/* { dg-final { scan-assembler-not "mov\[lq\]\?\t%\?\[er\].x, %\?\[er\].x" } }
*/
diff --git a/gcc/tree-outof-ssa.cc b/gcc/tree-outof-ssa.cc
index d340d4ba529..f285c81599e 100644
--- a/gcc/tree-outof-ssa.cc
+++ b/gcc/tree-outof-ssa.cc
@@ -1259,10 +1259,9 @@ insert_backedge_copies (void)
if (gimple_nop_p (def)
|| gimple_code (def) == GIMPLE_PHI)
continue;
- tree name = copy_ssa_name (result);
- gimple *stmt = gimple_build_assign (name, result);
imm_use_iterator imm_iter;
gimple *use_stmt;
+ auto_vec<use_operand_p, 8> uses;
/* The following matches trivially_conflicts_p. */
FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, result)
{
@@ -1273,11 +1272,51 @@ insert_backedge_copies (void)
{
use_operand_p use;
FOR_EACH_IMM_USE_ON_STMT (use, imm_iter)
- SET_USE (use, name);
+ uses.safe_push (use);
}
}
- gimple_stmt_iterator gsi = gsi_for_stmt (def);
- gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
+ /* When there is just a conflicting statement try to
+ adjust that to refer to the new definition.
+ In particular for now handle a conflict with the
+ use in a (exit) condition with a NE compare,
+ replacing a pre-IV-increment compare with a
+ post-IV-increment one. */
+ if (uses.length () == 1
+ && is_a <gcond *> (USE_STMT (uses[0]))
+ && gimple_cond_code (USE_STMT (uses[0])) == NE_EXPR
+ && is_gimple_assign (def)
+ && gimple_assign_rhs1 (def) == result
+ && (gimple_assign_rhs_code (def) == PLUS_EXPR
+ || gimple_assign_rhs_code (def) == MINUS_EXPR
+ || gimple_assign_rhs_code (def) == POINTER_PLUS_EXPR)
+ && TREE_CODE (gimple_assign_rhs2 (def)) == INTEGER_CST)
+ {
+ gcond *cond = as_a <gcond *> (USE_STMT (uses[0]));
+ tree *adj;
+ if (gimple_cond_lhs (cond) == result)
+ adj = gimple_cond_rhs_ptr (cond);
+ else
+ adj = gimple_cond_lhs_ptr (cond);
+ tree name = copy_ssa_name (result);
+ gimple *stmt
+ = gimple_build_assign (name,
+ gimple_assign_rhs_code (def),
+ *adj, gimple_assign_rhs2 (def));
+ gimple_stmt_iterator gsi = gsi_for_stmt (cond);
+ gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
+ *adj = name;
+ SET_USE (uses[0], arg);
+ update_stmt (cond);
+ }
+ else
+ {
+ tree name = copy_ssa_name (result);
+ gimple *stmt = gimple_build_assign (name, result);
+ gimple_stmt_iterator gsi = gsi_for_stmt (def);
+ gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
+ for (auto use : uses)
+ SET_USE (use, name);
+ }
}
}
}
--
2.43.0
