Update prebuilt Clang to r416183b from Android.

https://android.googlesource.com/platform/prebuilts/clang/host/
linux-x86/+/06a71ddac05c22edb2d10b590e1769b3f8619bef

clang 12.0.5 (based on r416183b) from build 7284624.

Change-Id: I277a316abcf47307562d8b748b84870f31a72866
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/linux-x64/clang/include/llvm/CodeGen/MachineBlockFrequencyInfo.h b/linux-x64/clang/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
index a438ecf..6c442d3 100644
--- a/linux-x64/clang/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
+++ b/linux-x64/clang/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
@@ -38,6 +38,9 @@
   static char ID;
 
   MachineBlockFrequencyInfo();
+  explicit MachineBlockFrequencyInfo(MachineFunction &F,
+                                     MachineBranchProbabilityInfo &MBPI,
+                                     MachineLoopInfo &MLI);
   ~MachineBlockFrequencyInfo() override;
 
   void getAnalysisUsage(AnalysisUsage &AU) const override;
@@ -55,16 +58,33 @@
   /// information. Please note that initial frequency is equal to 1024. It means
   /// that we should not rely on the value itself, but only on the comparison to
   /// the other block frequencies. We do this to avoid using of floating points.
-  ///
+  /// For example, to get the frequency of a block relative to the entry block,
+  /// divide the integral value returned by this function (the
+  /// BlockFrequency::getFrequency() value) by getEntryFreq().
   BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
 
+  /// Compute the frequency of the block, relative to the entry block.
+  /// This API assumes getEntryFreq() is non-zero.
+  float getBlockFreqRelativeToEntryBlock(const MachineBasicBlock *MBB) const {
+    return getBlockFreq(MBB).getFrequency() * (1.0f / getEntryFreq());
+  }
+
   Optional<uint64_t> getBlockProfileCount(const MachineBasicBlock *MBB) const;
   Optional<uint64_t> getProfileCountFromFreq(uint64_t Freq) const;
 
-  bool isIrrLoopHeader(const MachineBasicBlock *MBB);
+  bool isIrrLoopHeader(const MachineBasicBlock *MBB) const;
+
+  /// incrementally calculate block frequencies when we split edges, to avoid
+  /// full CFG traversal.
+  void onEdgeSplit(const MachineBasicBlock &NewPredecessor,
+                   const MachineBasicBlock &NewSuccessor,
+                   const MachineBranchProbabilityInfo &MBPI);
 
   const MachineFunction *getFunction() const;
   const MachineBranchProbabilityInfo *getMBPI() const;
+
+  /// Pop up a ghostview window with the current block frequency propagation
+  /// rendered using dot.
   void view(const Twine &Name, bool isSimple = true) const;
 
   // Print the block frequency Freq to OS using the current functions entry
@@ -76,6 +96,8 @@
   raw_ostream &printBlockFreq(raw_ostream &OS,
                               const MachineBasicBlock *MBB) const;
 
+  /// Divide a block's BlockFrequency::getFrequency() value by this value to
+  /// obtain the entry block - relative frequency of said block.
   uint64_t getEntryFreq() const;
 };