[all-commits] [llvm/llvm-project] 78a750: [Attributor] Track a GEP Instruction in align dedu...

[Hideto Ueno via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 78a750276f442726193b007a0010432765abe9d4
      https://github.com/llvm/llvm-project/commit/78a750276f442726193b007a0010432765abe9d4
  Author: Hideto Ueno <uenoku.tokotoko at gmail.com>
  Date:   2019-11-26 (Tue, 26 Nov 2019)

  Changed paths:
    M llvm/lib/Transforms/IPO/Attributor.cpp
    M llvm/test/Transforms/FunctionAttrs/align.ll
    M llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
    M llvm/test/Transforms/FunctionAttrs/nocapture.ll
    M llvm/test/Transforms/InferFunctionAttrs/dereferenceable.ll

  Log Message:
  -----------
  [Attributor] Track a GEP Instruction in align deduction

Summary:
This patch enables us to track GEP instruction in align deduction.
If a pointer `B` is defined as `A+Offset` and known to have alignment `C`, there exists some integer Q such that
```
 A + Offset = C * Q = B
```
 So we can say that the maximum power of two which is a divisor of gcd(Offset, C) is an alignment.

Reviewers: jdoerfert, sstefan1

Reviewed By: jdoerfert

Subscribers: lebedev.ri, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70392