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Author SHA1 Message Date
Roman Lebedev 0bde7c6527 [InstCombine] Shift amount reassociation: fixup constantexpr handling (PR42484) 
I was actually wondering if there was some nicer way than m_Value()+cast,
but apparently what i was really "subconsciously" thinking about
was correctness issue.

hasNoUnsignedWrap()/hasNoUnsignedWrap() exist for Instruction,
not for BinaryOperator, so let's just use m_Instruction(),
thus both avoiding a cast, and a crash.

Fixes https://bugs.llvm.org/show_bug.cgi?id=42484,
      https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15587

llvm-svn: 364915
 2019-07-02 12:54:48 +00:00
Roman Lebedev e3a94ba4a9 [InstCombine] Shift amount reassociation (PR42391) 
Summary:
Given pattern:
`(x shiftopcode Q) shiftopcode K`
we should rewrite it as
`x shiftopcode (Q+K)`  iff `(Q+K) u< bitwidth(x)`
This is valid for any shift, but they must be identical.

* https://rise4fun.com/Alive/9E2
* exact on both lshr => exact https://rise4fun.com/Alive/plHk
* exact on both ashr => exact https://rise4fun.com/Alive/QDAA
* nuw on both shl => nuw https://rise4fun.com/Alive/5Uk
* nsw on both shl => nsw https://rise4fun.com/Alive/0plg

Should fix [[ https://bugs.llvm.org/show_bug.cgi?id=42391 | PR42391]].

Reviewers: spatel, nikic, RKSimon

Reviewed By: nikic

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63812

llvm-svn: 364712
 2019-06-29 11:51:50 +00:00
Roman Lebedev 3b4f086df4 [NFC][InstCombine] Shift amount reassociation: revisit flag preservation tests 
llvm-svn: 364657
 2019-06-28 16:36:53 +00:00
Roman Lebedev 9f1dffdb02 [NFC][InstCombine] Shift amount reassociation: add flag preservation test 
As discussed in https://reviews.llvm.org/D63812#inline-569870
* exact on both lshr => exact https://rise4fun.com/Alive/plHk
* exact on both ashr => exact https://rise4fun.com/Alive/QDAA
* nuw on both shl => nuw https://rise4fun.com/Alive/5Uk
* nsw on both shl => nsw https://rise4fun.com/Alive/0plg

So basically if the same flag is set on both original shifts -> set it on new shift.
Don't think we can do anything with non-matching flags on shl.

llvm-svn: 364652
 2019-06-28 15:32:52 +00:00
Roman Lebedev 567eea44c2 [NFC][InstCombine] Add shift amount reassociation tests (PR42391) 
https://bugs.llvm.org/show_bug.cgi?id=42391
https://rise4fun.com/Alive/9E2

llvm-svn: 364393
 2019-06-26 08:17:05 +00:00