[memprof] Speed up llvm-profdata (#117446)

CallStackRadixTreeBuilder::build takes the parameter
MemProfFrameIndexes by value, involving copies:

  std::optional<const llvm::DenseMap<FrameIdTy, LinearFrameId>>
    MemProfFrameIndexes

Then "build" makes another copy of MemProfFrameIndexe and passes it to
encodeCallStack for every call stack, which is painfully slow.

This patch changes the type to a pointer so that we don't have to make
a copy every time we pass the argument.

Without this patch, it takes 553 seconds to run "llvm-profdata merge"
on a large MemProf raw profile.  This patch shortenes that down to 67
seconds.

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/ProfileData/InstrProfWriter.cpp b/llvm/lib/ProfileData/InstrProfWriter.cpp
index 4470e2c..d8ab18d 100644
--- a/llvm/lib/ProfileData/InstrProfWriter.cpp
+++ b/llvm/lib/ProfileData/InstrProfWriter.cpp
@@ -641,7 +641,7 @@ writeMemProfCallStackArray(
       MemProfCallStackIndexes;
 
   memprof::CallStackRadixTreeBuilder<memprof::FrameId> Builder;
-  Builder.build(std::move(MemProfCallStackData), MemProfFrameIndexes,
+  Builder.build(std::move(MemProfCallStackData), &MemProfFrameIndexes,
                 FrameHistogram);
   for (auto I : Builder.getRadixArray())
     OS.write32(I);