llvm/lib/Analysis
Mikael Holmen c14b5c3b1e [Lint] Don't warn about passing alloca'd value to tail call if using byval
Summary:
This fixes PR35241.

When using byval, the data is effectively copied as part of the call
anyway, so the pointer returned by the alloca will not be leaked to the
callee and thus there is no reason to issue a warning.

Reviewers: rnk

Reviewed By: rnk

Subscribers: Ka-Ka, llvm-commits

Differential Revision: https://reviews.llvm.org/D40009

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318279 91177308-0d34-0410-b5e6-96231b3b80d8
2017-11-15 07:46:48 +00:00
..
2016-08-25 01:29:55 +00:00
2017-07-09 05:54:44 +00:00
2017-10-01 00:09:53 +00:00
2016-04-18 09:17:29 +00:00
2017-02-14 17:21:12 +00:00
2017-08-25 12:38:53 +00:00

Analysis Opportunities:

//===---------------------------------------------------------------------===//

In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:

  {1,+,3,+,2}<loop>

Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as

  (-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))

In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.

//===---------------------------------------------------------------------===//

In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,

ScalarEvolution is forming this expression:

((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))

This could be folded to

(-1 * (trunc i64 undef to i32))

//===---------------------------------------------------------------------===//