[llvm] [llvm-exegesis] Align loop MBB in loop repetitor (PR #77264)

[Aiden Grossman via llvm-commits]

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@@ -74,6 +74,10 @@ class LoopSnippetRepetitor : public SnippetRepetitor {
       auto Loop = Filler.addBasicBlock();
       auto Exit = Filler.addBasicBlock();
 
+      // Align the loop machine basic block to a sixteen byte boundary
+      // so that instruction fetch on modern x86 platforms works optimally.
+      Loop.MBB->setAlignment(Align(16));
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boomanaiden154 wrote:

Thanks for the suggestion! That's definitely a lot cleaner. Currently X86 segfaults on this without passing a `MachineLoop` pointer which would be pretty difficult to get here. I've opened #77283 to fix the API issue. I'll land this patch after that one lands.

https://github.com/llvm/llvm-project/pull/77264