8303238: Create generalizations for existing LShift ideal transforms

jaskarth · cl4es · commit 8e41bf222f4a · 2023-03-13T11:10:42.000Z
Reviewed-by: redestad, thartmann
diff --git a/src/hotspot/share/opto/mulnode.cpp b/src/hotspot/share/opto/mulnode.cpp
@@ -847,21 +847,74 @@ Node *LShiftINode::Ideal(PhaseGVN *phase, bool can_reshape) {
     }
   }
 
-  // Check for "(x>>c0)<<c0" which just masks off low bits
-  if( (add1_op == Op_RShiftI || add1_op == Op_URShiftI ) &&
-      add1->in(2) == in(2) )
-    // Convert to "(x & -(1<<c0))"
-    return new AndINode(add1->in(1),phase->intcon( -(1<<con)));
-
-  // Check for "((x>>c0) & Y)<<c0" which just masks off more low bits
-  if( add1_op == Op_AndI ) {
+  // Check for "(x >> C1) << C2"
+  if (add1_op == Op_RShiftI || add1_op == Op_URShiftI) {
+    // Special case C1 == C2, which just masks off low bits
+    if (add1->in(2) == in(2)) {
+      // Convert to "(x & -(1 << C2))"
+      return new AndINode(add1->in(1), phase->intcon(-(1 << con)));
+    } else {
+      int add1Con = 0;
+      const_shift_count(phase, add1, &add1Con);
+
+      // Wait until the right shift has been sharpened to the correct count
+      if (add1Con > 0 && add1Con < BitsPerJavaInteger) {
+        // As loop parsing can produce LShiftI nodes, we should wait until the graph is fully formed
+        // to apply optimizations, otherwise we can inadvertently stop vectorization opportunities.
+        if (phase->is_IterGVN()) {
+          if (con > add1Con) {
+            // Creates "(x << (C2 - C1)) & -(1 << C2)"
+            Node* lshift = phase->transform(new LShiftINode(add1->in(1), phase->intcon(con - add1Con)));
+            return new AndINode(lshift, phase->intcon(-(1 << con)));
+          } else {
+            assert(con < add1Con, "must be (%d < %d)", con, add1Con);
+            // Creates "(x >> (C1 - C2)) & -(1 << C2)"
+
+            // Handle logical and arithmetic shifts
+            Node* rshift;
+            if (add1_op == Op_RShiftI) {
+              rshift = phase->transform(new RShiftINode(add1->in(1), phase->intcon(add1Con - con)));
+            } else {
+              rshift = phase->transform(new URShiftINode(add1->in(1), phase->intcon(add1Con - con)));
+            }
+
+            return new AndINode(rshift, phase->intcon(-(1 << con)));
+          }
+        } else {
+          phase->record_for_igvn(this);
+        }
+      }
+    }
+  }
+
+  // Check for "((x >> C1) & Y) << C2"
+  if (add1_op == Op_AndI) {
     Node *add2 = add1->in(1);
     int add2_op = add2->Opcode();
-    if( (add2_op == Op_RShiftI || add2_op == Op_URShiftI ) &&
-        add2->in(2) == in(2) ) {
-      // Convert to "(x & (Y<<c0))"
-      Node *y_sh = phase->transform( new LShiftINode( add1->in(2), in(2) ) );
-      return new AndINode( add2->in(1), y_sh );
+    if (add2_op == Op_RShiftI || add2_op == Op_URShiftI) {
+      // Special case C1 == C2, which just masks off low bits
+      if (add2->in(2) == in(2)) {
+        // Convert to "(x & (Y << C2))"
+        Node* y_sh = phase->transform(new LShiftINode(add1->in(2), phase->intcon(con)));
+        return new AndINode(add2->in(1), y_sh);
+      }
+
+      int add2Con = 0;
+      const_shift_count(phase, add2, &add2Con);
+      if (add2Con > 0 && add2Con < BitsPerJavaInteger) {
+        if (phase->is_IterGVN()) {
+          // Convert to "((x >> C1) << C2) & (Y << C2)"
+
+          // Make "(x >> C1) << C2", which will get folded away by the rule above
+          Node* x_sh = phase->transform(new LShiftINode(add2, phase->intcon(con)));
+          // Make "Y << C2", which will simplify when Y is a constant
+          Node* y_sh = phase->transform(new LShiftINode(add1->in(2), phase->intcon(con)));
+
+          return new AndINode(x_sh, y_sh);
+        } else {
+          phase->record_for_igvn(this);
+        }
+      }
     }
   }
 
@@ -970,21 +1023,74 @@ Node *LShiftLNode::Ideal(PhaseGVN *phase, bool can_reshape) {
     }
   }
 
-  // Check for "(x>>c0)<<c0" which just masks off low bits
-  if( (add1_op == Op_RShiftL || add1_op == Op_URShiftL ) &&
-      add1->in(2) == in(2) )
-    // Convert to "(x & -(1<<c0))"
-    return new AndLNode(add1->in(1),phase->longcon( -(CONST64(1)<<con)));
+  // Check for "(x >> C1) << C2"
+  if (add1_op == Op_RShiftL || add1_op == Op_URShiftL) {
+    // Special case C1 == C2, which just masks off low bits
+    if (add1->in(2) == in(2)) {
+      // Convert to "(x & -(1 << C2))"
+      return new AndLNode(add1->in(1), phase->longcon(-(CONST64(1) << con)));
+    } else {
+      int add1Con = 0;
+      const_shift_count(phase, add1, &add1Con);
+
+      // Wait until the right shift has been sharpened to the correct count
+      if (add1Con > 0 && add1Con < BitsPerJavaLong) {
+        // As loop parsing can produce LShiftI nodes, we should wait until the graph is fully formed
+        // to apply optimizations, otherwise we can inadvertently stop vectorization opportunities.
+        if (phase->is_IterGVN()) {
+          if (con > add1Con) {
+            // Creates "(x << (C2 - C1)) & -(1 << C2)"
+            Node* lshift = phase->transform(new LShiftLNode(add1->in(1), phase->intcon(con - add1Con)));
+            return new AndLNode(lshift, phase->longcon(-(CONST64(1) << con)));
+          } else {
+            assert(con < add1Con, "must be (%d < %d)", con, add1Con);
+            // Creates "(x >> (C1 - C2)) & -(1 << C2)"
+
+            // Handle logical and arithmetic shifts
+            Node* rshift;
+            if (add1_op == Op_RShiftL) {
+              rshift = phase->transform(new RShiftLNode(add1->in(1), phase->intcon(add1Con - con)));
+            } else {
+              rshift = phase->transform(new URShiftLNode(add1->in(1), phase->intcon(add1Con - con)));
+            }
+
+            return new AndLNode(rshift, phase->longcon(-(CONST64(1) << con)));
+          }
+        } else {
+          phase->record_for_igvn(this);
+        }
+      }
+    }
+  }
 
-  // Check for "((x>>c0) & Y)<<c0" which just masks off more low bits
-  if( add1_op == Op_AndL ) {
-    Node *add2 = add1->in(1);
+  // Check for "((x >> C1) & Y) << C2"
+  if (add1_op == Op_AndL) {
+    Node* add2 = add1->in(1);
     int add2_op = add2->Opcode();
-    if( (add2_op == Op_RShiftL || add2_op == Op_URShiftL ) &&
-        add2->in(2) == in(2) ) {
-      // Convert to "(x & (Y<<c0))"
-      Node *y_sh = phase->transform( new LShiftLNode( add1->in(2), in(2) ) );
-      return new AndLNode( add2->in(1), y_sh );
+    if (add2_op == Op_RShiftL || add2_op == Op_URShiftL) {
+      // Special case C1 == C2, which just masks off low bits
+      if (add2->in(2) == in(2)) {
+        // Convert to "(x & (Y << C2))"
+        Node* y_sh = phase->transform(new LShiftLNode(add1->in(2), phase->intcon(con)));
+        return new AndLNode(add2->in(1), y_sh);
+      }
+
+      int add2Con = 0;
+      const_shift_count(phase, add2, &add2Con);
+      if (add2Con > 0 && add2Con < BitsPerJavaLong) {
+        if (phase->is_IterGVN()) {
+          // Convert to "((x >> C1) << C2) & (Y << C2)"
+
+          // Make "(x >> C1) << C2", which will get folded away by the rule above
+          Node* x_sh = phase->transform(new LShiftLNode(add2, phase->intcon(con)));
+          // Make "Y << C2", which will simplify when Y is a constant
+          Node* y_sh = phase->transform(new LShiftLNode(add1->in(2), phase->intcon(con)));
+
+          return new AndLNode(x_sh, y_sh);
+        } else {
+          phase->record_for_igvn(this);
+        }
+      }
     }
   }
 
diff --git a/test/hotspot/jtreg/compiler/c2/irTests/LShiftINodeIdealizationTests.java b/test/hotspot/jtreg/compiler/c2/irTests/LShiftINodeIdealizationTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 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
@@ -27,7 +27,7 @@
 
 /*
  * @test
- * @bug 8297384
+ * @bug 8297384 8303238
  * @summary Test that Ideal transformations of LShiftINode* are being performed as expected.
  * @library /test/lib /
  * @run driver compiler.c2.irTests.LShiftINodeIdealizationTests
@@ -37,15 +37,21 @@ public static void main(String[] args) {
         TestFramework.run();
     }
 
-    @Run(test = { "test1", "test2" })
+    @Run(test = { "test1", "test2", "test3", "test4", "test5", "test6", "test7", "test8" })
     public void runMethod() {
         int a = RunInfo.getRandom().nextInt();
+        int b = RunInfo.getRandom().nextInt();
+        int c = RunInfo.getRandom().nextInt();
+        int d = RunInfo.getRandom().nextInt();
 
         int min = Integer.MIN_VALUE;
         int max = Integer.MAX_VALUE;
 
         assertResult(0);
         assertResult(a);
+        assertResult(b);
+        assertResult(c);
+        assertResult(d);
         assertResult(min);
         assertResult(max);
     }
@@ -54,6 +60,12 @@ public void runMethod() {
     public void assertResult(int a) {
         Asserts.assertEQ((a >> 2022) << 2022, test1(a));
         Asserts.assertEQ((a >>> 2022) << 2022, test2(a));
+        Asserts.assertEQ((a >> 4) << 8, test3(a));
+        Asserts.assertEQ((a >>> 4) << 8, test4(a));
+        Asserts.assertEQ((a >> 8) << 4, test5(a));
+        Asserts.assertEQ((a >>> 8) << 4, test6(a));
+        Asserts.assertEQ(((a >> 4) & 0xFF) << 8, test7(a));
+        Asserts.assertEQ(((a >>> 4) & 0xFF) << 8, test8(a));
     }
 
     @Test
@@ -71,4 +83,52 @@ public int test1(int x) {
     public int test2(int x) {
         return (x >>> 2022) << 2022;
     }
+
+    @Test
+    @IR(failOn = { IRNode.RSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks (x >> 4) << 8 => (x << 4) & -16
+    public int test3(int x) {
+        return (x >> 4) << 8;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.URSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks (x >>> 4) << 8 => (x << 4) & -16
+    public int test4(int x) {
+        return (x >>> 4) << 8;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.LSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.RSHIFT, "1" })
+    // Checks (x >> 8) << 4 => (x >> 4) & -16
+    public int test5(int x) {
+        return (x >> 8) << 4;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.LSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.URSHIFT, "1" })
+    // Checks (x >>> 8) << 4 => (x >>> 4) & -16
+    public int test6(int x) {
+        return (x >>> 8) << 4;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.RSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks ((x >> 4) & 0xFF) << 8 => (x << 4) & 0xFF00
+    public int test7(int x) {
+        return ((x >> 4) & 0xFF) << 8;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.URSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks ((x >>> 4) & 0xFF) << 8 => (x << 4) & 0xFF00
+    public int test8(int x) {
+        return ((x >>> 4) & 0xFF) << 8;
+    }
 }
diff --git a/test/hotspot/jtreg/compiler/c2/irTests/LShiftLNodeIdealizationTests.java b/test/hotspot/jtreg/compiler/c2/irTests/LShiftLNodeIdealizationTests.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2023, 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.
+ */
+package compiler.c2.irTests;
+
+import jdk.test.lib.Asserts;
+import compiler.lib.ir_framework.*;
+
+/*
+ * @test
+ * @bug 8303238
+ * @summary Test that Ideal transformations of LShiftLNode* are being performed as expected.
+ * @library /test/lib /
+ * @run driver compiler.c2.irTests.LShiftLNodeIdealizationTests
+ */
+public class LShiftLNodeIdealizationTests {
+    public static void main(String[] args) {
+        TestFramework.run();
+    }
+
+    @Run(test = { "test3", "test4", "test5", "test6", "test7", "test8" })
+    public void runMethod() {
+        long a = RunInfo.getRandom().nextLong();
+        long b = RunInfo.getRandom().nextLong();
+        long c = RunInfo.getRandom().nextLong();
+        long d = RunInfo.getRandom().nextLong();
+
+        long min = Long.MIN_VALUE;
+        long max = Long.MAX_VALUE;
+
+        assertResult(0);
+        assertResult(a);
+        assertResult(b);
+        assertResult(c);
+        assertResult(d);
+        assertResult(min);
+        assertResult(max);
+    }
+
+    @DontCompile
+    public void assertResult(long a) {
+        Asserts.assertEQ((a >> 4L) << 8L, test3(a));
+        Asserts.assertEQ((a >>> 4L) << 8L, test4(a));
+        Asserts.assertEQ((a >> 8L) << 4L, test5(a));
+        Asserts.assertEQ((a >>> 8L) << 4L, test6(a));
+        Asserts.assertEQ(((a >> 4L) & 0xFFL) << 8L, test7(a));
+        Asserts.assertEQ(((a >>> 4L) & 0xFFL) << 8L, test8(a));
+    }
+
+    @Test
+    @IR(failOn = { IRNode.RSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks (x >> 4) << 8 => (x << 4) & -16
+    public long test3(long x) {
+        return (x >> 4L) << 8L;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.URSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks (x >>> 4) << 8 => (x << 4) & -16
+    public long test4(long x) {
+        return (x >>> 4L) << 8L;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.LSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.RSHIFT, "1" })
+    // Checks (x >> 8) << 4 => (x >> 4) & -16
+    public long test5(long x) {
+        return (x >> 8L) << 4L;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.LSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.URSHIFT, "1" })
+    // Checks (x >>> 8) << 4 => (x >>> 4) & -16
+    public long test6(long x) {
+        return (x >>> 8L) << 4L;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.RSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks ((x >> 4) & 0xFF) << 8 => (x << 4) & 0xFF00
+    public long test7(long x) {
+        return ((x >> 4L) & 0xFFL) << 8L;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.URSHIFT })
+    @IR(counts = { IRNode.AND, "1", IRNode.LSHIFT, "1" })
+    // Checks ((x >>> 4) & 0xFF) << 8 => (x << 4) & 0xFF00
+    public long test8(long x) {
+        return ((x >>> 4L) & 0xFFL) << 8L;
+    }
+}
diff --git a/test/micro/org/openjdk/bench/vm/compiler/LShiftNodeIdealize.java b/test/micro/org/openjdk/bench/vm/compiler/LShiftNodeIdealize.java
