diff mbox series

[2/2] tree-optimization/114099 - virtual LC PHIs and early exit vect

Message ID 20240226113527.95D523858409@sourceware.org
State New
Headers show
Series [1/2] tree-optimization/114068 - missed virtual LC PHI after vect peeling | expand

Commit Message

Richard Biener Feb. 26, 2024, 11:34 a.m. UTC 
In some cases exits can lack LC PHI nodes for the virtual operand.
We have to create them when the epilog loop requires them which also
allows us to remove some only halfway correct fixups.  This is the
variant triggering for alternate exits.

Bootstrap and regtest pending on x86_64-unknown-linux-gnu.

	PR tree-optimization/114099
	* tree-vect-loop-manip.cc (slpeel_tree_duplicate_loop_to_edge_cfg):
	Create and fill in a needed virtual LC PHI for the alternate
	exits.  Remove code dealing with that missing.

	* gcc.dg/vect/vect-early-break_120-pr114099.c: New testcase.
---
 .../vect/vect-early-break_120-pr114099.c      | 20 +++++++++++
 gcc/tree-vect-loop-manip.cc                   | 35 +++++++------------
 2 files changed, 33 insertions(+), 22 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/vect-early-break_120-pr114099.c
diff mbox series

Patch

diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_120-pr114099.c b/gcc/testsuite/gcc.dg/vect/vect-early-break_120-pr114099.c
new file mode 100644
index 00000000000..77e47e30417
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_120-pr114099.c
@@ -0,0 +1,20 @@ 
+/* { dg-do compile } */
+/* { dg-add-options vect_early_break } */
+/* { dg-require-effective-target vect_early_break } */
+/* { dg-require-effective-target vect_int } */
+/* { dg-additional-options "-O3" } */
+
+/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
+
+int m;
+void __attribute__((noreturn)) n();
+void t1(int jj, int l) {
+  for (int i = 1; i < l; i++)
+  {
+    int p = m++;
+    if (p)
+      n();
+    if(jj <= i)
+      __builtin_unreachable();
+  }
+}
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 39bac1e99ef..137b053ac35 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -1667,17 +1667,18 @@  slpeel_tree_duplicate_loop_to_edge_cfg (class loop *loop, edge loop_exit,
 		  alt_loop_exit_block = split_edge (exit);
 		if (!need_virtual_phi)
 		  continue;
-		if (vphi_def)
-		  {
-		    if (!vphi)
-		      vphi = create_phi_node (copy_ssa_name (vphi_def),
-					      alt_loop_exit_block);
-		    else
-		      /* Edge redirection might re-allocate the PHI node
-			 so we have to rediscover it.  */
-		      vphi = get_virtual_phi (alt_loop_exit_block);
-		    add_phi_arg (vphi, vphi_def, exit, UNKNOWN_LOCATION);
-		  }
+		/* When the edge has no virtual LC PHI get at the live
+		   virtual operand by other means.  */
+		if (!vphi_def)
+		  vphi_def = get_live_virtual_operand_on_edge (exit);
+		if (!vphi)
+		  vphi = create_phi_node (copy_ssa_name (vphi_def),
+					  alt_loop_exit_block);
+		else
+		  /* Edge redirection might re-allocate the PHI node
+		     so we have to rediscover it.  */
+		  vphi = get_virtual_phi (alt_loop_exit_block);
+		add_phi_arg (vphi, vphi_def, exit, UNKNOWN_LOCATION);
 	      }
 
 	  set_immediate_dominator (CDI_DOMINATORS, new_preheader,
@@ -1789,17 +1790,7 @@  slpeel_tree_duplicate_loop_to_edge_cfg (class loop *loop, edge loop_exit,
 		  if (virtual_operand_p (alt_arg))
 		    {
 		      gphi *vphi = get_virtual_phi (alt_loop_exit_block);
-		      /* ???  When the exit yields to a path without
-			 any virtual use we can miss a LC PHI for the
-			 live virtual operand.  Simply choosing the
-			 one live at the start of the loop header isn't
-			 correct, but we should get here only with
-			 early-exit vectorization which will move all
-			 defs after the main exit, so leave a temporarily
-			 wrong virtual operand in place.  This happens
-			 for gcc.c-torture/execute/20150611-1.c  */
-		      if (vphi)
-			alt_arg = gimple_phi_result (vphi);
+		      alt_arg = gimple_phi_result (vphi);
 		    }
 		  /* For other live args we didn't create LC PHI nodes.
 		     Do so here.  */