31 lines
1006 B
Plaintext
31 lines
1006 B
Plaintext
|
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))
|
||
|
|
|
||
|
|
//===---------------------------------------------------------------------===//
|