mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-01-31 10:34:17 +00:00
ac5b42cad8
r216771 introduced a change to MemoryDependenceAnalysis that allowed it to reason about acquire/release operations. However, this change does not ensure that the acquire/release operations pair. Unfortunately, this leads to miscompiles as we won't see an acquire load as properly memory effecting. This largely reverts r216771. This fixes PR22708. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232889 91177308-0d34-0410-b5e6-96231b3b80d8
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))
//===---------------------------------------------------------------------===//