Commit Graph

5 Commits

Author SHA1 Message Date
David Majnemer
48164ed24d InstSimplify: Don't simplify gep X, (Y-X) to Y if types differ
It's incorrect to perform this simplification if the types differ.
A bitcast would need to be inserted for this to work.

This fixes PR20771.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216597 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-27 20:08:34 +00:00
Nico Weber
1c768816d7 Reland r216439 215441, majnemer has a real fix for PR20771.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216586 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-27 20:06:19 +00:00
Nico Weber
b2f71836eb Revert r216439 (and r216441, else the former doesn't revert cleanly).
It caused PR 20771. I'll land a test on the clang side.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216582 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-27 20:00:13 +00:00
David Majnemer
8058ffeb18 InstSimplify: Fold gep X, (sub 0, ptrtoint(X)) to null
Save InstCombine some work if we can perform this fold during
InstSimplify.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216441 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-26 07:08:03 +00:00
David Majnemer
594e4a1dd3 InstSimplify: Simplify trivial pointer expressions like b + (e - b)
consider:
long long *f(long long *b, long long *e) {
  return b + (e - b);
}

we would lower this to something like:
define i64* @f(i64* %b, i64* %e) {
  %1 = ptrtoint i64* %e to i64
  %2 = ptrtoint i64* %b to i64
  %3 = sub i64 %1, %2
  %4 = ashr exact i64 %3, 3
  %5 = getelementptr inbounds i64* %b, i64 %4
  ret i64* %5
}

This should fold away to just 'e'.

N.B.  This adds m_SpecificInt as a convenient way to match against a
particular 64-bit integer when using LLVM's match interface.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216439 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-26 05:55:16 +00:00