From: Richard Biener <rguenther@suse.de>
Date: Mon, 3 Feb 2025 14:12:52 +0000 (+0100)
Subject: tree-optimization/117113 - ICE with unroll-and-jam
X-Git-Tag: releases/gcc-12.5.0~36
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f4dbdeabb2944d014d506a537a576a6f9a1f4c1f;p=thirdparty%2Fgcc.git

tree-optimization/117113 - ICE with unroll-and-jam

When there's an inner loop without virtual header PHI but the outer
loop has one the fusion process cannot handle the need to create
an inner loop virtual header PHI.  Punt in this case.

	PR tree-optimization/117113
	* gimple-loop-jam.cc (unroll_jam_possible_p): Detect when
	we cannot handle virtual SSA update.

	* gcc.dg/torture/pr117113.c: New testcase.

(cherry picked from commit 0675eb17480bada678bf2769d39732027abcd6d0)
---

diff --git a/gcc/gimple-loop-jam.cc b/gcc/gimple-loop-jam.cc
index e33dd9091df..22d518d9fb0 100644
--- a/gcc/gimple-loop-jam.cc
+++ b/gcc/gimple-loop-jam.cc
@@ -278,13 +278,17 @@ unroll_jam_possible_p (class loop *outer, class loop *loop)
      body would be the after-iter value of the first body) if it's over
      an associative and commutative operation.  We wouldn't
      be able to handle unknown cycles.  */
+  bool inner_vdef = false;
   for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi))
     {
       affine_iv iv;
       tree op = gimple_phi_result (psi.phi ());
 
       if (virtual_operand_p (op))
-	continue;
+	{
+	  inner_vdef = true;
+	  continue;
+	}
       if (!simple_iv (loop, loop, op, &iv, true))
 	return false;
       /* The inductions must be regular, loop invariant step and initial
@@ -300,6 +304,12 @@ unroll_jam_possible_p (class loop *outer, class loop *loop)
 	 copy, _not_ the next value of the second body.  */
     }
 
+  /* When there's no inner loop virtual PHI IV we cannot handle the update
+     required to the inner loop if that doesn't already have one.  See
+     PR117113.  */
+  if (!inner_vdef && get_virtual_phi (outer->header))
+    return false;
+
   return true;
 }
 
diff --git a/gcc/testsuite/gcc.dg/torture/pr117113.c b/gcc/testsuite/gcc.dg/torture/pr117113.c
new file mode 100644
index 00000000000..e90ad034a4d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr117113.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fno-tree-dce -fno-inline" } */
+
+int a, b, c;
+volatile int d[1];
+void e() {}
+void f(int g) {}
+int main() {
+  int i;
+  for (; b; b--) {
+    for (i = 0; i < 3; i++) {
+      e();
+      f(d[0]);
+      d[0];
+    }
+    if (a)
+      c++;
+  }
+  return 0;
+}