Changeset 191978 in webkit

Timestamp:

Nov 3, 2015 2:13:52 PM (8 years ago)

Author:

mark.lam@apple.com

Message:

Fix some inefficiencies in the baseline usage of JITAddGenerator.
​https://bugs.webkit.org/show_bug.cgi?id=150850

Reviewed by Michael Saboff.

1. emit_op_add() was loading the operands twice. Removed the redundant load.
2. The snippet may decide that it wants to go the slow path route all the time. In that case, emit_op_add will end up emitting a branch to an out of line slow path followed by some dead code to store the result of the fast path on to the stack. We now check if the snippet determined that there's no fast path, and just emit the slow path inline, and skip the dead store of the fast path result.

• jit/JITArithmetic.cpp:

(JSC::JIT::emit_op_add):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• jit/JITArithmetic.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2015-11-03  Mark Lam  <mark.lam@apple.com>
+
+        Fix some inefficiencies in the baseline usage of JITAddGenerator.
+        https://bugs.webkit.org/show_bug.cgi?id=150850
+
+        Reviewed by Michael Saboff.
+
+        1. emit_op_add() was loading the operands twice.  Removed the redundant load.
+        2. The snippet may decide that it wants to go the slow path route all the time.
+           In that case, emit_op_add will end up emitting a branch to an out of line
+           slow path followed by some dead code to store the result of the fast path
+           on to the stack.
+           We now check if the snippet determined that there's no fast path, and just
+           emit the slow path inline, and skip the dead store of the fast path result.
+
+        * jit/JITArithmetic.cpp:
+        (JSC::JIT::emit_op_add):
+
 2015-11-03  Filip Pizlo  <fpizlo@apple.com>
 

trunk/Source/JavaScriptCore/jit/JITArithmetic.cpp

@@ -933 +933 @@
 #endif
 
-    emitGetVirtualRegister(op1, leftRegs);
-    emitGetVirtualRegister(op2, rightRegs);
-
     bool leftIsConstInt32 = isOperandConstantInt(op1);
     bool rightIsConstInt32 = isOperandConstantInt(op2);
@@ -969 +966 @@
 
     gen.generateFastPath(*this);
-    gen.endJumpList().link(this);
-    emitPutVirtualRegister(result, resultRegs);
-
-    addSlowCase(gen.slowPathJumpList());
+
+    if (!gen.endJumpList().empty()) {
+        gen.endJumpList().link(this);
+        emitPutVirtualRegister(result, resultRegs);
+        
+        addSlowCase(gen.slowPathJumpList());
+    } else {
+        gen.slowPathJumpList().link(this);
+        JITSlowPathCall slowPathCall(this, currentInstruction, slow_path_add);
+        slowPathCall.call();
+    }
 }