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Re: [Patch-86512]: Subnormal float support in armv7(with -msoft-float) for intrinsics


Nicolas Pitre wrote:

>> However if r4 is non-zero, the carry will be set, and the tsths will be executed. This
>> clears the carry and sets the Z flag based on bit 20.
>
> No, not at all. The carry is not affected. And that's the point of the 
> tst instruction here rather than a cmp: it sets the N and Z flags but 
> leaves C alone as there is no shifter involved.

No, the carry is always set by logical operations with a shifted immediate. It is only
unchanged if the immediate uses a zero rotate. So any shifted immediate > 255
will set the carry. This is detailed in the Arm Architecture Reference Manual, eg.
see the pseudo code for A32ExpandImm_C in LSL (immediate).

Wilco

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