gcc/ChangeLog
2020-10-05 Jiufu Guo <guoji...@linux.ibm.com>
* tree-ssa-loop.h (clean_up_loop_closed_phi): New declaration.
* tree-ssa-loop.c (tree_ssa_loop_done): Call
clean_up_loop_closed_phi.
* tree-ssa-propagate.c (propagate_rhs_into_lhs): New function.
gcc/testsuite/ChangeLog
2020-10-05 Jiufu Guo <guoji...@linux.ibm.com>
* gcc.dg/tree-ssa/loopclosedphi.c: New test.
---
gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c | 21 +++
gcc/tree-ssa-loop.c | 1 +
gcc/tree-ssa-loop.h | 1 +
gcc/tree-ssa-propagate.c | 120
++++++++++++++++++
4 files changed, 143 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
b/gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
new file mode 100644
index 00000000000..d71b757fbca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-tree-ch -w -fdump-tree-loopdone-details" }
*/
+
+void
+t6 (int qz, int wh)
+{
+ int jl = wh;
+
+ while (1.0 * qz / wh < 1)
+ {
+ qz = wh * (wh + 2);
+
+ while (wh < 1)
+ jl = 0;
+ }
+
+ while (qz < 1)
+ qz = jl * wh;
+}
+
+/* { dg-final { scan-tree-dump-times "Replacing" 2 "loopdone"} } */
diff --git a/gcc/tree-ssa-loop.c b/gcc/tree-ssa-loop.c
index 5e8365d4e83..7d680b2f5d2 100644
--- a/gcc/tree-ssa-loop.c
+++ b/gcc/tree-ssa-loop.c
@@ -530,6 +530,7 @@ tree_ssa_loop_done (void)
free_numbers_of_iterations_estimates (cfun);
scev_finalize ();
loop_optimizer_finalize ();
+ clean_up_loop_closed_phi (cfun);
return 0;
}
diff --git a/gcc/tree-ssa-loop.h b/gcc/tree-ssa-loop.h
index 9e35125e6e8..baa940b9d1e 100644
--- a/gcc/tree-ssa-loop.h
+++ b/gcc/tree-ssa-loop.h
@@ -67,6 +67,7 @@ public:
extern bool for_each_index (tree *, bool (*) (tree, tree *, void *),
void *);
extern char *get_lsm_tmp_name (tree ref, unsigned n, const char
*suffix = NULL);
extern unsigned tree_num_loop_insns (class loop *, struct eni_weights
*);
+extern unsigned clean_up_loop_closed_phi (function *);
/* Returns the loop of the statement STMT. */
diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index 87dbf55fab9..813143852b9 100644
--- a/gcc/tree-ssa-propagate.c
+++ b/gcc/tree-ssa-propagate.c
@@ -1549,4 +1549,123 @@ propagate_tree_value_into_stmt
(gimple_stmt_iterator *gsi, tree val)
else
gcc_unreachable ();
}
+
+/* Propagate RHS into all uses of LHS (when possible).
+
+ RHS and LHS are derived from STMT, which is passed in solely so
+ that we can remove it if propagation is successful. */
+
+static bool
+propagate_rhs_into_lhs (gphi *stmt, tree lhs, tree rhs)
+{
+ use_operand_p use_p;
+ imm_use_iterator iter;
+ gimple_stmt_iterator gsi;
+ gimple *use_stmt;
+ bool changed = false;
+ bool all = true;
+
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Replacing '");
+ print_generic_expr (dump_file, lhs, dump_flags);
+ fprintf (dump_file, "' with '");
+ print_generic_expr (dump_file, rhs, dump_flags);
+ fprintf (dump_file, "'\n");
+ }
+
+ /* Walk over every use of LHS and try to replace the use with RHS.
*/
+ FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
+ {
+ /* It is not safe to propagate into below stmts. */
+ if (gimple_debug_bind_p (use_stmt)
+ || (gimple_code (use_stmt) == GIMPLE_ASM
+ && !may_propagate_copy_into_asm (lhs))
+ || (TREE_CODE (rhs) == SSA_NAME
+ && SSA_NAME_DEF_STMT (rhs) == use_stmt))
+ {
+ all = false;
+ continue;
+ }
+
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Original statement:");
+ print_gimple_stmt (dump_file, use_stmt, 0, dump_flags);
+ }
+
+ /* Propagate the RHS into this use of the LHS. */
+ FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+ propagate_value (use_p, rhs);
+
+ /* Propagation may expose new operands to the renamer. */
+ update_stmt (use_stmt);
+
+ /* If variable index is replaced with a constant, then
+ update the invariant flag for ADDR_EXPRs. */
+ if (gimple_assign_single_p (use_stmt)
+ && TREE_CODE (gimple_assign_rhs1 (use_stmt)) == ADDR_EXPR)
+ recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1
(use_stmt));
+
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Updated statement:");
+ print_gimple_stmt (dump_file, use_stmt, 0, dump_flags);
+ }
+
+ changed = true;
+ }
+
+ /* Remove the degenerate PHI node. */
+ if (all)
+ {
+ gsi = gsi_for_stmt (stmt);
+ remove_phi_node (&gsi, true);
+ }
+
+ return changed;
+}
+
+/* Check exits of each loop in FUN, walk over loop closed PHIs in
+ each exit basic block and propagate degenerate PHIs. */
+
+unsigned
+clean_up_loop_closed_phi (function *fun)
+{
+ unsigned i;
+ edge e;
+ gphi *phi;
+ tree rhs;
+ tree lhs;
+ gphi_iterator gsi;
+ struct loop *loop;
+ bool cfg_altered = false;
+
+ /* Walk over loop in function. */
+ FOR_EACH_LOOP_FN (fun, loop, 0)
+ {
+ /* Check each exit edge of loop. */
+ auto_vec<edge> exits = get_loop_exit_edges (loop);
+ FOR_EACH_VEC_ELT (exits, i, e)
+ if (single_pred_p (e->dest))
+ /* Walk over loop-closed PHIs. */
+ for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);)
+ {
+ phi = gsi.phi ();
+ rhs = degenerate_phi_result (phi);
+ lhs = gimple_phi_result (phi);
+
+ /* Advance the iterator before stmt is removed. */
+ gsi_next (&gsi);
+
+ if (rhs && !virtual_operand_p (lhs)
+ && may_propagate_copy (lhs, rhs))
+ cfg_altered |= propagate_rhs_into_lhs (phi, lhs, rhs);
+ }
+ }
+
+ return cfg_altered;
+}
--
2.25.1