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Wei Mi
f2885f7297
We found current sampleFDO had a performance issue when triaging a regression. For a callsite with inline instance in the profile, even if hot callsite inliner cannot inline it, it may still execute enough times and should not be treated as cold in regular inliner later. However, currently if such callsite is not inlined by hot callsite inliner, and the BB where the callsite locates doesn't get samples from other instructions inside of it, the callsite will have no profile metadata annotated. In regular inliner cost analysis, if the callsite has no profile annotated and its caller has profile information, it will be treated as cold. The fix changes the isCallsiteHot check and chooses to compare CallsiteTotalSamples with hot cutoff value computed by ProfileSummaryInfo. Differential Revision: https://reviews.llvm.org/D45377 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332058 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))
//===---------------------------------------------------------------------===//