Avoid calling ToRegister(register) when result is in register already, and register is shared.

Review URL: http://codereview.chromium.org/1325004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4260 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/virtual-frame-ia32.cc

@@ -1040,18 +1040,23 @@ Result VirtualFrame::CallKeyedStoreIC() {
   PrepareForCall(0, 0);
   if (!cgen()->allocator()->is_used(eax) ||
       (value.is_register() && value.reg().is(eax))) {
-    value.ToRegister(eax);  // No effect if value is in eax already.
+    if (!cgen()->allocator()->is_used(eax)) {
+      value.ToRegister(eax);
+    }
     MoveResultsToRegisters(&key, &receiver, ecx, edx);
     value.Unuse();
   } else if (!cgen()->allocator()->is_used(ecx) ||
              (key.is_register() && key.reg().is(ecx))) {
-    // Receiver and/or key are in eax.
-    key.ToRegister(ecx);
+    if (!cgen()->allocator()->is_used(ecx)) {
+      key.ToRegister(ecx);
+    }
     MoveResultsToRegisters(&value, &receiver, eax, edx);
     key.Unuse();
   } else if (!cgen()->allocator()->is_used(edx) ||
              (receiver.is_register() && receiver.reg().is(edx))) {
-    receiver.ToRegister(edx);
+    if (!cgen()->allocator()->is_used(edx)) {
+      receiver.ToRegister(edx);
+    }
     MoveResultsToRegisters(&key, &value, ecx, eax);
     receiver.Unuse();
   } else {

test/mjsunit/codegen-coverage.js

@@ -33,6 +33,13 @@ function identity(x) {
   return x;
 }
 
+function lookup(w, a) {
+  // This function tests a code path in the generation of a keyed load IC
+  // where the key and the value are both in the same register.
+  a = a;
+  w[a] = a;
+}
+
 function cover_codegen_paths() {
   var x = 1;
 
@@ -131,6 +138,12 @@ function cover_codegen_paths() {
     assertEquals(1073741824, 1 - di);
 
     x = 3;
+    var w = { };
+    lookup(w, x);
+    lookup(w, x);
+    lookup(w, x);
+
+    x = 3;  // Terminate while loop.
   }
 }