mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2025-01-10 22:00:58 +00:00
4874f5bce5
implements something out of Target/README.txt producing: _foo: ## @foo movl 4(%esp), %eax movapd LCPI1_0, %xmm0 movapd %xmm0, (%eax) ret $4 instead of: _foo: ## @foo movl 4(%esp), %eax movapd _b, %xmm0 mulpd LCPI1_0, %xmm0 addpd _a, %xmm0 movapd %xmm0, (%eax) ret $4 llvm-svn: 84942
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.
//===---------------------------------------------------------------------===//