[llvm] [SandboxVec] Tag insts in a Region with metadata. (PR #109353)

[via llvm-commits]

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@@ -13,13 +13,25 @@ namespace llvm::sandboxir {
 Region::Region(Context &Ctx) : Ctx(Ctx) {
   static unsigned StaticRegionID;
   RegionID = StaticRegionID++;
+
+  LLVMContext &LLVMCtx = Ctx.LLVMCtx;
+  auto *RegionStrMD = MDString::get(LLVMCtx, RegionStr);
+  auto *RegionIDMD = llvm::ConstantAsMetadata::get(
+      llvm::ConstantInt::get(LLVMCtx, APInt(sizeof(RegionID) * 8, RegionID)));
+  RegionMDN = MDNode::get(LLVMCtx, {RegionStrMD, RegionIDMD});
 }
 
 Region::~Region() {}
 
-void Region::add(Instruction *I) { Insts.insert(I); }
+void Region::add(Instruction *I) {
+  Insts.insert(I);
+  cast<llvm::Instruction>(I->Val)->setMetadata(MDKind, RegionMDN);
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vporpo wrote:

Let's also add a TODO about a potential redesign where we tag instructions lazily, perhaps at the end of the region pass manager, to save compile time. It might be worth exploring in the future.

https://github.com/llvm/llvm-project/pull/109353