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Summary: To enable profile-guided indirect call promotion in ThinLTO mode, we simply add call graph edges for each profitable target from the profile to the summaries, then the summary-guided importing will consider the callee for importing as usual. Also we need to enable the indirect call promotion pass creation in the PassManagerBuilder when PerformThinLTO=true (we are in the ThinLTO backend), so that the newly imported functions are considered for promotion in the backends. The IC promotion profiles refer to callees by GUID, which required adding GUIDs to the per-module VST in bitcode (and assigning them valueIds similar to how they are assigned valueIds in the combined index). Reviewers: mehdi_amini, xur Subscribers: mehdi_amini, davidxl, llvm-commits Differential Revision: http://reviews.llvm.org/D21932 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275707 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))
//===---------------------------------------------------------------------===//