Fix PR 103317, ICE after PHI-OPT, minmax_replacement producing invalid SSA

The problem is r12-5300-gf98f373dd822b35c allows phiopt to recognize more basic blocks
but missed one location where the basic block does not need to be empty but still
needs to have a single predecessor. This patch fixes that over sight.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/103317

gcc/ChangeLog:

	* tree-ssa-phiopt.c (minmax_replacement): For the non empty
	middle bb case, check to make sure it has a single predecessor.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr103317-1.c: New test.

gcc/testsuite/gcc.c-torture/compile/pr103317-1.c

@@ -0,0 +1,13 @@
+int a, b;
+char c;
+void
+d (void)
+{
+  char e = c;
+  if (b)
+    if (c < 16 - 11)
+      e = 16 - 11;
+  if (e > 8)
+    e = 8;
+  a = e;
+}

gcc/tree-ssa-phiopt.c

@@ -1780,6 +1780,9 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
       gimple *assign = last_and_only_stmt (middle_bb);
       tree lhs, op0, op1, bound;
 
+      if (!single_pred_p (middle_bb))
+	return false;
+
       if (!assign
 	  || gimple_code (assign) != GIMPLE_ASSIGN)
 	return false;