[llvm] [CodeLayout] Size-aware machine block placement (PR #109711)

[via llvm-commits]

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@@ -3589,13 +3607,15 @@ void MachineBlockPlacement::applyExtTsp() {
     CurrentBlockOrder.push_back(&MBB);
   }
 
-  auto BlockSizes = std::vector<uint64_t>(F->size());
-  auto BlockCounts = std::vector<uint64_t>(F->size());
+  std::vector<uint64_t> BlockCounts(F->size());
+  std::vector<uint64_t> BlockSizes(F->size());
   std::vector<codelayout::EdgeCount> JumpCounts;
+  SmallVector<MachineOperand, 4> Cond; // For analyzeBranch.
+  SmallVector<const MachineBasicBlock *, 4> Succs;
   for (MachineBasicBlock &MBB : *F) {
     // Getting the block frequency.
     BlockFrequency BlockFreq = MBFI->getBlockFreq(&MBB);
-    BlockCounts[BlockIndex[&MBB]] = BlockFreq.getFrequency();
+    BlockCounts[BlockIndex[&MBB]] = OptForSize ? 1 : BlockFreq.getFrequency();
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spupyrev wrote:

> If BlockFreq.getFrequency() is zero, shouldn't it remain zero even if OptForSize is true?
IIRC we don't have blocks with zero-frequency; it is always positive, but might be very small for never-executed blocks.

https://github.com/llvm/llvm-project/pull/109711