Changeset 197445 in webkit

Timestamp:

Mar 1, 2016, 11:53:20 PM (11 years ago)

Author:

benjamin@webkit.org

Message:

[JSC] Simplify ArithMod(ArithMod(x, const1), const2) if const2 >= const1
​https://bugs.webkit.org/show_bug.cgi?id=154904

Reviewed by Saam Barati.

The ASM test "ubench" has a "x % 10 % 255".
The second modulo should be eliminated.

This is a 15% improvement on ASMJS' ubench.

• dfg/DFGStrengthReductionPhase.cpp:

(JSC::DFG::StrengthReductionPhase::handleNode):

• tests/stress/arith-modulo-twice.js: Added.

(opaqueModuloSmaller):
(opaqueModuloEqual):
(opaqueModuloLarger):
(opaqueModuloSmallerNeg):
(opaqueModuloEqualNeg):
(opaqueModuloLargerNeg):
(opaqueExpectedOther):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• dfg/DFGStrengthReductionPhase.cpp (modified) (2 diffs)
• tests/stress/arith-modulo-twice.js (added)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2016-03-01  Benjamin Poulain  <benjamin@webkit.org>
+
+        [JSC] Simplify ArithMod(ArithMod(x, const1), const2) if const2 >= const1
+        https://bugs.webkit.org/show_bug.cgi?id=154904
+
+        Reviewed by Saam Barati.
+
+        The ASM test "ubench" has a "x % 10 % 255".
+        The second modulo should be eliminated.
+
+        This is a 15% improvement on ASMJS' ubench.
+
+        * dfg/DFGStrengthReductionPhase.cpp:
+        (JSC::DFG::StrengthReductionPhase::handleNode):
+        * tests/stress/arith-modulo-twice.js: Added.
+        (opaqueModuloSmaller):
+        (opaqueModuloEqual):
+        (opaqueModuloLarger):
+        (opaqueModuloSmallerNeg):
+        (opaqueModuloEqualNeg):
+        (opaqueModuloLargerNeg):
+        (opaqueExpectedOther):
+
 2016-03-01  Ryosuke Niwa  <rniwa@webkit.org>
 

trunk/Source/JavaScriptCore/dfg/DFGStrengthReductionPhase.cpp

@@ -37 +37 @@
 #include "DFGVariableAccessDataDump.h"
 #include "JSCInlines.h"
+#include <cstdlib>
 
 namespace JSC { namespace DFG {
@@ -170 +171 @@
                     m_changed = true;
                 }
+            }
+            break;
+
+        case ArithMod:
+            // On Integers
+            // In: ArithMod(ArithMod(x, const1), const2)
+            // Out: Identity(ArithMod(x, const1))
+            //     if const1 <= const2.
+            if (m_node->binaryUseKind() == Int32Use
+                && m_node->child2()->isInt32Constant()
+                && m_node->child1()->op() == ArithMod
+                && m_node->child1()->binaryUseKind() == Int32Use
+                && m_node->child1()->child2()->isInt32Constant()
+                && std::abs(m_node->child1()->child2()->asInt32()) <= std::abs(m_node->child2()->asInt32())) {
+                    convertToIdentityOverChild1();
             }
             break;