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

test/mjsunit/codegen-coverage.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --nofull-compiler --nofast-compiler
 
 // Test paths in the code generator where values in specific registers
 // get moved around.
 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;
 
   // This test depends on the fixed order of register allocation.  We try to
   // get values in specific registers (ia32, x64):
   var a;   // Register eax, rax.
   var b;   // Register ebx, rbx.
   var c;   // Register ecx, rcx.
   var d;   // Register edx, rdx.
   var di;  // Register edi, rdi.
@@ skipping 78 matching lines @@
 
     x = identity(-1073741824);
     a = x + 1;
     b = x + 1;
     c = x + 1;
     d = x + 1;
     di = x + 1;
     assertEquals(1073741824, 1 - di);
 
     x = 3;
+    var w = { };
+    lookup(w, x);
+    lookup(w, x);
+    lookup(w, x);
+
+    x = 3;  // Terminate while loop.
   }
 }
 
 cover_codegen_paths();