[llvm] [X86] Reimplement bundle alignment mode (PR #175830)

[via llvm-commits]

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@@ -116,6 +116,14 @@ cl::opt<bool> X86PadForBranchAlign(
     "x86-pad-for-branch-align", cl::init(true), cl::Hidden,
     cl::desc("Pad previous instructions to implement branch alignment"));
 
+cl::opt<bool> X86PrefixPadForBundle(
+    "x86-prefix-pad-for-bundle", cl::init(false), cl::Hidden,
+    cl::desc("Pad using prefixes to align instruction bundles"));
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t-noh wrote:

I could reuse `X86PadForAlign`, but its description doesn't quite match this use case. I’m leaning towards removing it entirely and checking if `X86PadMaxPrefixSize > 0` instead—especially since `X86RelaxForBundle` is gone. Let me know your opinion.

https://github.com/llvm/llvm-project/pull/175830