[llvm] [MachineBlockPlacement][X86] Use max of MDAlign and TLIAlign to align Loops. (PR #71026)

[Freddy Ye via llvm-commits]

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@@ -151,6 +151,54 @@ MachineLoopInfo::findLoopPreheader(MachineLoop *L, bool SpeculativePreheader,
   return Preheader;
 }
 
+MDNode *MachineLoop::getLoopID() const {
+  MDNode *LoopID = nullptr;
+  if (auto *MBB = findLoopControlBlock()) {
+    // If there is a single latch block, then the metadata
+    // node is attached to its terminating instruction.
+    const auto *BB = MBB->getBasicBlock();
+    if (!BB)
+      return nullptr;
+    if (const auto *TI = BB->getTerminator())
+      LoopID = TI->getMetadata(LLVMContext::MD_loop);
+  } else if (auto *MBB = getHeader()) {
+    // There seem to be multiple latch blocks, so we have to
+    // visit all predecessors of the loop header and check
+    // their terminating instructions for the metadata.
+    if (const auto *H = MBB->getBasicBlock()) {
+      // Walk over all blocks in the loop.
+      for (auto *MBB : this->blocks()) {
+        const auto *BB = MBB->getBasicBlock();
+        if (!BB)
+          return nullptr;
+        const auto *TI = BB->getTerminator();
+        if (!TI)
+          return nullptr;
+        MDNode *MD = nullptr;
+        // Check if this terminating instruction jumps to the loop header.
+        for (const auto *S : successors(TI)) {
+          if (S == H) {
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FreddyLeaf wrote:

Addressed in latest commit.

https://github.com/llvm/llvm-project/pull/71026