Rebase for retesting.

Fixed according to comment.

Simon, thanks! I agree that operands have same type. Do you think that it is better to create new node? Or the latest uploaded version where I update the operand of smax is acceptable?

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• Sorry, but initially I did not understand your concern. Fixed the code, so that existing node with changed operands is returned.

Simon, could you please write if my comment is not enough and you need more details or clarification.

(truncate (smin (smax (x, C1), C2)) to dest_type)
is equivalent to
(truncate (umin (smax(x, C1), unsigned_max_of_dest_type)) to dest_type)
that is why I don't need to create any node and just return smax.

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Sorry, forgot to commit one of the tests. WIll fix.

• Added detection of the smax(smin) pattern.

• Fixed according to comments.

• Addressed review comments.

Sanjay, thank you very much! I agree that solution with helper function looks better.

Improved comment.

Oh, yes, it is clear for me now. Thanks! I have fixed according to your recommendation.

Fixed according to comments.

For using constant from cmp instruction (instead of recreation) we will need to check that truncated constant is equal to lower bits of cmp constant.
That is why I decided just to recreate constant which looks like more general solution.

Minimized test cases and added new ones.

We need to check that predicate is signed before matching patterns after clamp.
This condition was removed by mistake. Fixed.

Rebase after committing foldICmpWithZero as a separate change.
Also made changes according to comments.

Sanjay, no, I don't have. I have asked my colleague to commit. Thanks!

I have read more carefully your comment. As far as I understood in D26556 you want to change the process of decision making for function that folds cast operation into select.
According to suggestion from Eli you should try to match the size of a select to a cmp of its condition operand as a final result.
Necessary to mention that this function doesn't make cast folding when select is min/max and it is called only when select is an operand of cast operation.

I have checked that patch from D26556 doesn't work for the case described in this review.
D26556 is about folding extension instruction into select.
I.e. in case of the following pattern:

s = select Cond, C1, C2 
sext s

sext operation is eliminated and C1, C2 constants are widened.

Fixed comment.

Created separate patch to move folding of cmp instruction: D38934. I will be able to update this differential revision when it will be committed.
I have renamed function so that we will be able to add an smax sibling for this fold with separate commit.

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