[LLVMdev] How to handle size_t in front ends?

[Chris Lattner]

On Wed, 7 May 2008, Jonathan S. Shapiro wrote:
> On Wed, 2008-05-07 at 16:09 -0700, Chris Lattner wrote:
>> On Wed, 7 May 2008, Jonathan S. Shapiro wrote:
>>>>
>>>> i64 should be big enough for this.  Just use i64.
>>>
>>> On a 32-bit platform, doesn't one want to use i32?
>>
>> Why?  What is wrong with i64?
>
> On its face, the problem is that it doesn't fit in a native register...
> or is there something here that I am failing to understand?

The code generator deletes dead upper parts.  For example:

int test(long long a, long long b) {
   return a+b;  // 64-bit add, taking low 32-bits
}

compiles to a single add, even on x86-32:

_test:
 	movl	12(%esp), %eax
 	addl	4(%esp), %eax
 	ret

-Chris

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