[MBFIWrapper] Add a new function getBlockProfileCount

MBFIWrapper keeps track of block frequencies of newly created blocks and
modified blocks, modified block frequencies should also impact block profile
count. This class doesn't provide interface getBlockProfileCount, users can only
use the underlying MBFI to query profile count, the underlying MBFI doesn't know
the modifications made in MBFIWrapper, so it either provides stale profile count
for modified block or simply crashes on new blocks.

So this patch add function getBlockProfileCount to class MBFIWrapper to handle
new blocks or modified blocks.

Differential Revision: https://reviews.llvm.org/D87802

diff --git a/llvm/include/llvm/CodeGen/MBFIWrapper.h b/llvm/include/llvm/CodeGen/MBFIWrapper.h
index 062431a..bcbf3ee 100644 (file)
--- a/llvm/include/llvm/CodeGen/MBFIWrapper.h
+++ b/llvm/include/llvm/CodeGen/MBFIWrapper.h
@@ -28,6 +28,8 @@ class MBFIWrapper {
 
   BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
   void setBlockFreq(const MachineBasicBlock *MBB, BlockFrequency F);
+  Optional<uint64_t> getBlockProfileCount(const MachineBasicBlock *MBB) const;
+
   raw_ostream &printBlockFreq(raw_ostream &OS,
                               const MachineBasicBlock *MBB) const;
   raw_ostream &printBlockFreq(raw_ostream &OS,

diff --git a/llvm/lib/CodeGen/MBFIWrapper.cpp b/llvm/lib/CodeGen/MBFIWrapper.cpp
index 5110f75..4755def 100644 (file)
--- a/llvm/lib/CodeGen/MBFIWrapper.cpp
+++ b/llvm/lib/CodeGen/MBFIWrapper.cpp
@@ -30,6 +30,18 @@ void MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB,
   MergedBBFreq[MBB] = F;
 }
 
+Optional<uint64_t>
+MBFIWrapper::getBlockProfileCount(const MachineBasicBlock *MBB) const {
+  auto I = MergedBBFreq.find(MBB);
+
+  // Modified block frequency also impacts profile count. So we should compute
+  // profile count from new block frequency if it has been changed.
+  if (I != MergedBBFreq.end())
+    return MBFI.getProfileCountFromFreq(I->second.getFrequency());
+
+  return MBFI.getBlockProfileCount(MBB);
+}
+
 raw_ostream & MBFIWrapper::printBlockFreq(raw_ostream &OS,
                                           const MachineBasicBlock *MBB) const {
   return MBFI.printBlockFreq(OS, getBlockFreq(MBB));

diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index e32ea57..8a86696 100644 (file)
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -418,7 +418,7 @@ class MachineBlockPlacement : public MachineFunctionPass {
   /// The return value is used to model tail duplication cost.
   BlockFrequency getBlockCountOrFrequency(const MachineBasicBlock *BB) {
     if (UseProfileCount) {
-      auto Count = MBFI->getMBFI().getBlockProfileCount(BB);
+      auto Count = MBFI->getBlockProfileCount(BB);
       if (Count)
         return *Count;
       else