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[X86][AArch64][DAGCombine] Unfold 'check for [no] signed truncation' pattern

Description

[X86][AArch64][DAGCombine] Unfold 'check for [no] signed truncation' pattern

Summary:

PR38149

As discussed in https://reviews.llvm.org/D49179#1158957 and later,
the IR for 'check for [no] signed truncation' pattern can be improved:
https://rise4fun.com/Alive/gBf
^ that pattern will be produced by Implicit Integer Truncation sanitizer,
https://reviews.llvm.org/D48958 https://bugs.llvm.org/show_bug.cgi?id=21530
in signed case, therefore it is probably a good idea to improve it.

But the IR-optimal patter does not lower efficiently, so we want to undo it..

This handles the simple pattern.
There is a second pattern with predicate and constants inverted.

NOTE: we do not check uses here. we always do the transform.

Reviewers: spatel, craig.topper, RKSimon, javed.absar

Reviewed By: spatel

Subscribers: kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D49266

Details

Committed
lebedevriJul 16 2018, 5:44 AM
Reviewer
spatel
Differential Revision
D49266: [X86][AArch64][DAGCombine] Unfold 'check for [no] signed truncation' pattern
Parents
rL337165: [Sparc] Use the correct encoding for ta 3
Branches
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