fast-mode code generator.

AST expression nodes are annotated with a location when doing the
initial syntactic check of the AST.  In the current implementation,
expression locations are 'temporary' (ie, allocated to the stack) or
'nowhere' (ie, the expression's value is not needed though it must be
evaluated for side effects).

For the assignment '.result = true' on IA32, we had before (with the
true value already on top of the stack):

32  mov eax,[esp]
35  mov [ebp+0xf4],eax
38  pop eax

Now:

32  pop [ebp+0xf4]


======== On x64, before:

37  movq rax,[rsp]
41  movq [rbp-0x18],rax
45  pop rax

Now:

37  pop [rbp-0x18]


======== On ARM, before (with the true value in register ip):

36  str ip, [sp, #-4]!
40  ldr ip, [sp, #+0]
44  str ip, [fp, #-12]
48  add sp, sp, #4

Now:

36  str ip, [fp, #-12]


Review URL: http://codereview.chromium.org/267118

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3076 ce2b1a6d-e550-0410-aec6-3dcde31c8c00