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Author SHA1 Message Date
David Majnemer 11ca2971e8 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.

llvm-svn: 216597
 2014-08-27 20:08:34 +00:00
Nico Weber 48c82400ed Reland r216439 215441, majnemer has a real fix for PR20771. 
llvm-svn: 216586
 2014-08-27 20:06:19 +00:00
Nico Weber 7b343e3cc6 Revert r216439 (and r216441, else the former doesn't revert cleanly). 
It caused PR 20771. I'll land a test on the clang side.

llvm-svn: 216582
 2014-08-27 20:00:13 +00:00
David Majnemer 788d0ab8c8 InstSimplify: Fold gep X, (sub 0, ptrtoint(X)) to null 
Save InstCombine some work if we can perform this fold during
InstSimplify.

llvm-svn: 216441
 2014-08-26 07:08:03 +00:00
David Majnemer bc4981323f 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.

llvm-svn: 216439
 2014-08-26 05:55:16 +00:00