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Chandler Carruth
ee48043ceb
functions. In the prior commit, we provide ordering to the LCG between functions and library function definitions that they might begin to call through transformations. But we still would delete these library functions from the call graph if they became dead during inlining. While this immediately crashed, it also exposed a loss of information. We shouldn't remove definitions of library functions that can still usefully participate in the LCG-powered CGSCC optimization process. If new call edges are formed, we want to have definitions to be called. We can still remove these functions if truly dead using global-dce, etc, but removing them during the CGSCC walk is premature. This fixes a crash in the new PM when optimizing some unusual libraries that end up with "internal" lib functions such as the code in the "R" language's libraries. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308417 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))
//===---------------------------------------------------------------------===//