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Nikita Popov
f715eda604
This patch combines the "has" and "get" parts of the cache access. getCachedValueInfo() now both sets the BBLV return argument, and returns whether the value was found. Additionally, the management of the work stack is now integrated into getBlockValue(). If the value is not cached yet, we try to push to the stack (and return false, indicating that we need to solve first), or return overdefined in case of a cycle. These changes a) avoid a duplicate cache lookup for has & get and b) ensure that the logic is uniform everywhere. For this reason this change is also not quite NFC, because previously overdefined values from the cache, and overdefined values from a cycle received different treatment when it came to assumption intersection. Differential Revision: https://reviews.llvm.org/D76788
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))
//===---------------------------------------------------------------------===//