8275847: Scheduling fails with "too many D-U pinch points" on small method

Reviewed-by: thartmann, kvn

Author: nick-arm

src/hotspot/cpu/x86/vmreg_x86.hpp

@@ -90,7 +90,13 @@ inline   bool is_concrete() {
 #ifndef AMD64
   if (is_Register()) return true;
 #endif // AMD64
-  return is_even(value());
+  // Do not use is_XMMRegister() here as it depends on the UseAVX setting.
+  if (value() >= ConcreteRegisterImpl::max_fpr && value() < ConcreteRegisterImpl::max_xmm) {
+    int base = value() - ConcreteRegisterImpl::max_fpr;
+    return base % XMMRegisterImpl::max_slots_per_register == 0;
+  } else {
+    return is_even(value());   // General, float, and K registers are all two slots wide
+  }
 }
 
 #endif // CPU_X86_VMREG_X86_HPP

src/hotspot/share/opto/buildOopMap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 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
@@ -231,10 +231,6 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i
 
     VMReg r = OptoReg::as_VMReg(OptoReg::Name(reg), framesize, max_inarg_slot);
 
-    if (false && r->is_reg() && !r->is_concrete()) {
-      continue;
-    }
-
     // See if dead (no reaching def).
     Node *def = _defs[reg];     // Get reaching def
     assert( def, "since live better have reaching def" );
@@ -312,14 +308,10 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i
           set_live_bit(live,breg);
           // Already missed our turn?
           if( breg < reg ) {
-            if (b->is_stack() || b->is_concrete() || true ) {
-              omap->set_oop( b);
-            }
+            omap->set_oop(b);
           }
         }
-        if (b->is_stack() || b->is_concrete() || true ) {
-          omap->set_derived_oop( r, b);
-        }
+        omap->set_derived_oop(r, b);
       }
 
     } else if( t->isa_narrowoop() ) {
@@ -347,9 +339,7 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i
       assert( dup_check[_callees[reg]]==0, "trying to callee save same reg twice" );
       debug_only( dup_check[_callees[reg]]=1; )
       VMReg callee = OptoReg::as_VMReg(OptoReg::Name(_callees[reg]));
-      if ( callee->is_concrete() || true ) {
-        omap->set_callee_saved( r, callee);
-      }
+      omap->set_callee_saved(r, callee);
 
     } else {
       // Other - some reaching non-oop value

src/hotspot/share/opto/output.cpp

@@ -2915,6 +2915,16 @@ void Scheduling::anti_do_def( Block *b, Node *def, OptoReg::Name def_reg, int is
   if( !OptoReg::is_valid(def_reg) ) // Ignore stores & control flow
     return;
 
+  if (OptoReg::is_reg(def_reg)) {
+    VMReg vmreg = OptoReg::as_VMReg(def_reg);
+    if (vmreg->is_reg() && !vmreg->is_concrete() && !vmreg->prev()->is_concrete()) {
+      // This is one of the high slots of a vector register.
+      // ScheduleAndBundle already checked there are no live wide
+      // vectors in this method so it can be safely ignored.
+      return;
+    }
+  }
+
   Node *pinch = _reg_node[def_reg]; // Get pinch point
   if ((pinch == NULL) || _cfg->get_block_for_node(pinch) != b || // No pinch-point yet?
       is_def ) {    // Check for a true def (not a kill)

test/hotspot/jtreg/compiler/c2/irTests/TestScheduleSmallMethod.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, Arm Limited. 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.
+ */
+
+package compiler.c2.irTests;
+
+import jdk.test.lib.Asserts;
+import compiler.lib.ir_framework.*;
+
+/*
+ * @test
+ * @bug 8275847
+ * @requires vm.compiler2.enabled
+ * @summary Test that small method with runtime calls can be scheduled.
+ * @library /test/lib /
+ * @run driver compiler.c2.irTests.TestScheduleSmallMethod
+ */
+public class TestScheduleSmallMethod {
+
+    public static void main(String[] args) {
+        TestFramework framework = new TestFramework();
+        Scenario schedulerOn = new Scenario(0, "-XX:+OptoScheduling");
+        Scenario schedulerOff = new Scenario(1, "-XX:-OptoScheduling");
+        framework.addScenarios(schedulerOn, schedulerOff).start();
+    }
+
+    @Test
+    public double testSmallMethodTwoRuntimeCalls(double value) {
+        // The two intrinsified Math calls below caused the scheduler to
+        // bail out with "too many D-U pinch points". See bug 8275847.
+        return Math.log(Math.sin(value));
+    }
+
+    @Run(test = "testSmallMethodTwoRuntimeCalls")
+    public void checkTestSmallMethodTwoRuntimeCalls() throws Throwable {
+        Asserts.assertLessThan(testSmallMethodTwoRuntimeCalls(Math.PI/2), 0.00001);
+    }
+}