Duncan Sands bbc7016c60 Transform code like this
%V = mul i64 %N, 4
 %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V
into
 %t1 = getelementptr i32* %arr, i32 %N
 %t = bitcast i32* %t1 to i8*
incorporating the multiplication into the getelementptr.
This happens all the time in dragonegg, for example for
  int foo(int *A, int N) {
    return A[N];
  }
because gcc turns this into byte pointer arithmetic before it hits the plugin:
  D.1590_2 = (long unsigned int) N_1(D);
  D.1591_3 = D.1590_2 * 4;
  D.1592_5 = A_4(D) + D.1591_3;
  D.1589_6 = *D.1592_5;
  return D.1589_6;
The D.1592_5 line is a POINTER_PLUS_EXPR, which is turned into a getelementptr
on a bitcast of A_4 to i8*, so this becomes exactly the kind of IR that the
transform fires on.

An analogous transform (with no testcases!) already existed for bitcasts of
arrays, so I rewrote it to share code with this one.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166474 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-23 08:28:26 +00:00
..
2012-10-02 15:49:34 +00:00
2012-10-23 08:28:26 +00:00
2012-06-08 22:30:05 +00:00
2012-04-23 17:39:52 +00:00

This directory contains test cases for the instcombine transformation.  The
dated tests are actual bug tests, whereas the named tests are used to test
for features that the this pass should be capable of performing.