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3 Commits

Author SHA1 Message Date
Sanjoy Das 6e9b355cc9 Revert "[SCEV] Add nuw/nsw to mul ops in StrengthenNoWrapFlags" 
This reverts r334428.  It incorrectly marks some multiplications as nuw.  Tim
Shen is working on a proper fix.

Original commit message:

[SCEV] Add nuw/nsw to mul ops in StrengthenNoWrapFlags where safe.

Summary:
Previously we would add them for adds, but not multiplies.

llvm-svn: 335016
 2018-06-19 04:09:44 +00:00
Justin Lebar aa4fec94d8 [SCEV] Add nuw/nsw to mul ops in StrengthenNoWrapFlags where safe. 
Summary:
Previously we would add them for adds, but not multiplies.

Reviewers: sanjoy

Subscribers: llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D48038

llvm-svn: 334428
 2018-06-11 18:57:42 +00:00
Zhaoshi Zheng e3c9070f06 Model ashr(shl(x, n), m) as mul(x, 2^(n-m)) when n > m 
Given below case:

  %y = shl %x, n
  %z = ashr %y, m

when n = m, SCEV models it as sext(trunc(x)). This patch tries to handle
the case where n > m by using sext(mul(trunc(x), 2^(n-m)))) as the SCEV
expression.

llvm-svn: 298631
 2017-03-23 18:06:09 +00:00