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

[Fangrui Song via llvm-commits]

================
@@ -316,6 +334,82 @@ void MCELFStreamer::emitIdent(StringRef IdentString) {
   popSection();
 }
 
+void MCELFStreamer::emitBundleAlignMode(Align Alignment) {
+  if (Log2(Alignment) > 30)
+    getContext().reportError(getStartTokLoc(),
+                             ".bundle_align_mode alignment must be <= 30");
+  MCAssembler &Assembler = getAssembler();
+  setAllowAutoPadding(true);
+
+  if (Alignment > 1 && (Assembler.getBundleAlignSize() == 0 ||
+                        Assembler.getBundleAlignSize() == Alignment.value()))
+    Assembler.setBundleAlignSize(Alignment.value());
+  else
+    getContext().reportError(getStartTokLoc(),
+                             ".bundle_align_mode cannot be changed once set");
+}
+
+void MCELFStreamer::emitBundleLock(bool AlignToEnd,
+                                   const MCSubtargetInfo &STI) {
+  MCSection &Sec = *getCurrentSectionOnly();
+  auto &Asm = getAssembler();
+
+  if (!Asm.isBundlingEnabled()) {
+    getContext().reportError(
+        getStartTokLoc(), ".bundle_lock forbidden when bundling is disabled");
+    return;
+  }
+
+  if (Sec.isBundleLocked()) {
+    getContext().reportError(getStartTokLoc(),
+                             "nested .bundle_lock is not allowed");
+    return;
+  }
+  Sec.setIsBundleLocked(true);
+
+  auto AlignBoundary = Asm.getBundleAlignSize();
+  BundleBA =
+      newSpecialFragment<MCBoundaryAlignFragment>(Align(AlignBoundary), STI);
+  BundleBA->setAlignToEnd(AlignToEnd);
+}
+
+void MCELFStreamer::emitBundleUnlock(const MCSubtargetInfo &STI) {
+  MCSection &Sec = *getCurrentSectionOnly();
+
+  if (!getAssembler().isBundlingEnabled()) {
+    getContext().reportError(
+        getStartTokLoc(), ".bundle_unlock forbidden when bundling is disabled");
----------------
MaskRay wrote:

Untested. The lock-side equivalent is covered by `lock-without-mode.s`, but this unlock-side error has no test. Add a `.bundle_unlock` with no preceding `.bundle_align_mode` to `bundle-errors.s`.

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