On 1/12/2015 4:40 PM, deadalnix wrote:
These are trash register. Meaning the callee can put whatever in them. The
caller must consider them trashed after the call.

So no, it do NOT increase register pressure.

1. the register must be assigned a value - that has a cost
2. functions often get inlined
3. it prevents EDX from being used by the return value, when the return value is larger than a single register size 4. static functions may not need to follow the C ABI register convention, and can be so optimized

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