8268366: Incorrect calculation of has_fpu_registers in C1 linear scan

Reviewed-by: kvn, chagedorn

src/hotspot/share/c1/c1_LinearScan.cpp

@@ -643,7 +643,8 @@ void LinearScan::compute_local_live_sets() {
         CodeEmitInfo* info = visitor.info_at(k);
         ValueStack* stack = info->stack();
         for_each_state_value(stack, value,
-          set_live_gen_kill(value, op, live_gen, live_kill)
+          set_live_gen_kill(value, op, live_gen, live_kill);
+          local_has_fpu_registers = local_has_fpu_registers || value->type()->is_float_kind();
         );
       }
 
@@ -1659,22 +1660,33 @@ void LinearScan::allocate_registers() {
   Interval* precolored_cpu_intervals, *not_precolored_cpu_intervals;
   Interval* precolored_fpu_intervals, *not_precolored_fpu_intervals;
 
-  // allocate cpu registers
+  // collect cpu intervals
   create_unhandled_lists(&precolored_cpu_intervals, &not_precolored_cpu_intervals,
                          is_precolored_cpu_interval, is_virtual_cpu_interval);
 
-  // allocate fpu registers
+  // collect fpu intervals
   create_unhandled_lists(&precolored_fpu_intervals, &not_precolored_fpu_intervals,
                          is_precolored_fpu_interval, is_virtual_fpu_interval);
-
-  // the fpu interval allocation cannot be moved down below with the fpu section as
+  // this fpu interval collection cannot be moved down below with the allocation section as
   // the cpu_lsw.walk() changes interval positions.
 
+  if (!has_fpu_registers()) {
+#ifdef ASSERT
+    assert(not_precolored_fpu_intervals == Interval::end(), "missed an uncolored fpu interval");
+#else
+    if (not_precolored_fpu_intervals != Interval::end()) {
+      BAILOUT("missed an uncolored fpu interval");
+    }
+#endif
+  }
+
+  // allocate cpu registers
   LinearScanWalker cpu_lsw(this, precolored_cpu_intervals, not_precolored_cpu_intervals);
   cpu_lsw.walk();
   cpu_lsw.finish_allocation();
 
   if (has_fpu_registers()) {
+    // allocate fpu registers
     LinearScanWalker fpu_lsw(this, precolored_fpu_intervals, not_precolored_fpu_intervals);
     fpu_lsw.walk();
     fpu_lsw.finish_allocation();

test/hotspot/jtreg/compiler/c1/TestLinearScanHasFPURegisters.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8268366
+ * @run main/othervm -Xbatch -XX:+TieredCompilation -XX:TieredStopAtLevel=1
+ *                   compiler.c1.TestLinearScanHasFPURegisters
+ */
+
+package compiler.c1;
+
+public class TestLinearScanHasFPURegisters {
+    void test(String[] args) {
+        String arr[] = new String[4];
+        float f = -1;
+        try {
+            arr[0] = "-1"; // exception edge 1 with value -1
+            if (args.length > 1) {
+                f = 42;
+                arr[1] = "42"; // exception edge 2 with value 42
+            }
+        } catch (Exception e) {
+            // exception handler block with incoming phi for "f"
+            for (int i = 0; i < 1; ++i) {
+                f = f; // generates bytecodes, but no JIT IR
+            }
+        }
+    }
+    public static void main(String[] args) {
+        TestLinearScanHasFPURegisters t = new TestLinearScanHasFPURegisters();
+        for (int i = 0; i < 1000; ++i) {
+            t.test(args);
+        }
+    }
+}