Question about lowering clamp function to bic/usat on ARM

Hi,

Given a function like x < 0 ? 0 : x

We can lower it to bic x, x, asr 31 because we can test if CC==LT && RHS==TrueVal==0 && LHS==FalseVal

Further, give a function x > 255 ? 255 : (x < 0 ? 0 :x), we should lower it to: usat x, #8

However, things become more complicated if we have

((x < 0 ? 0 :x) << n ) & mask …

Because it will first be converted to

x < 0 ? 0 : ((x << n) & mask)

Now, it’s hard to match the pattern. (Doable but nasty)

Any suggestions?

Thanks in advance.

Weiming

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