From 286cda3461d6f5ce7d911d3f26bd4975ea7ea11d Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Mon, 1 Jul 2024 10:06:55 +0200
Subject: [PATCH] tree-optimization/115723 - ICE with .COND_ADD reduction

The following fixes an ICE with a .COND_ADD discovered as reduction
even though its else value isn't the reduction chain link but a
constant.  This would be wrong-code with --disable-checking I think.

	PR tree-optimization/115723
	* tree-vect-loop.cc (check_reduction_path): For a .COND_ADD
	verify the else value also refers to the reduction chain op.

	* gcc.dg/vect/pr115723.c: New testcase.
---
 gcc/testsuite/gcc.dg/vect/pr115723.c | 25 +++++++++++++++++++++++++
 gcc/tree-vect-loop.cc                | 12 ++++++++----
 2 files changed, 33 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr115723.c

diff --git a/gcc/testsuite/gcc.dg/vect/pr115723.c b/gcc/testsuite/gcc.dg/vect/pr115723.c
new file mode 100644
index 00000000000..b98b29d4870
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr115723.c
@@ -0,0 +1,25 @@
+/* { dg-additional-options "-ffast-math -fno-unsafe-math-optimizations" } */
+
+#include "tree-vect.h"
+
+double __attribute__((noipa))
+foo (double *x, double *y, int n)
+{
+  double res = 0.;
+  for (int i = 0; i < n; ++i)
+    if (y[i] > 0.)
+      res += x[i];
+    else
+      res = 64.;
+  return res;
+}
+
+double y[16] = { 1., 1., 1., 1., 0., 1., 1., 1.,
+                 1., 1., 1., 1., 1., 1., 1., 1. };
+int main ()
+{
+  check_vect ();
+  if (foo (y, y, 16) != 64. + 11.)
+    abort ();
+  return 0;
+}
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 3095ff5ab6b..a64b5082bd1 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -4163,15 +4163,19 @@ pop:
 
       FOR_EACH_IMM_USE_STMT (op_use_stmt, imm_iter, op.ops[opi])
 	{
-	/* In case of a COND_OP (mask, op1, op2, op1) reduction we might have
-	   op1 twice (once as definition, once as else) in the same operation.
-	   Allow this.  */
+	  /* In case of a COND_OP (mask, op1, op2, op1) reduction we should
+	     have op1 twice (once as definition, once as else) in the same
+	     operation.  Enforce this.  */
 	  if (cond_fn_p && op_use_stmt == use_stmt)
 	    {
 	      gcall *call = as_a<gcall *> (use_stmt);
 	      unsigned else_pos
 		= internal_fn_else_index (internal_fn (op.code));
-
+	      if (gimple_call_arg (call, else_pos) != op.ops[opi])
+		{
+		  fail = true;
+		  break;
+		}
 	      for (unsigned int j = 0; j < gimple_call_num_args (call); ++j)
 		{
 		  if (j == else_pos)