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Teresa Johnson
9274a9b246
Summary: The function section prefix for PGO based layout (e.g. hot/unlikely) should look at the hotness of all blocks not just the entry BB. A function with a cold entry but a very hot loop should be placed in the hot section, for example, so that it is located close to other hot functions it may call. For SamplePGO it was already looking at the branch weights on calls, and I made that code conditional on whether this is SamplePGO since it was essentially a noop for instrumentation PGO anyway. Reviewers: davidxl Subscribers: eraman, llvm-commits Differential Revision: https://reviews.llvm.org/D41395 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321197 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))
//===---------------------------------------------------------------------===//