[llvm] [IR] Add CallBr intrinsics support (PR #133907)

[Nikita Popov via llvm-commits]

================
@@ -3507,16 +3507,39 @@ void SelectionDAGBuilder::visitInvoke(const InvokeInst &I) {
                           DAG.getBasicBlock(Return)));
 }
 
+/// The intrinsics currently supported by callbr are implicit control flow
+/// intrinsics such as amdgcn.kill.
+/// - they should be called (no "dontcall-" attributes)
+/// - they do not touch memory on the target (= !TLI.getTgtMemIntrinsic())
+/// - they do not need custom argument handling (no
+/// TLI.CollectTargetIntrinsicOperands())
+void SelectionDAGBuilder::visitCallBrIntrinsic(const CallBrInst &I) {
+  auto [HasChain, OnlyLoad] = getTargetIntrinsicCallProperties(I);
+
+  SmallVector<SDValue, 8> Ops =
+      getTargetIntrinsicOperands(I, HasChain, OnlyLoad);
+  SDVTList VTs = getTargetIntrinsicVTList(I, HasChain);
+
+  // Create the node.
+  SDValue Result =
+      getTargetNonMemIntrinsicNode(*I.getType(), HasChain, Ops, VTs);
+  Result = handleTargetIntrinsicRet(I, HasChain, OnlyLoad, Result);
+
+  setValue(&I, Result);
+}
+
 void SelectionDAGBuilder::visitCallBr(const CallBrInst &I) {
   MachineBasicBlock *CallBrMBB = FuncInfo.MBB;
 
-  // Deopt bundles are lowered in LowerCallSiteWithDeoptBundle, and we don't
-  // have to do anything here to lower funclet bundles.
-  failForInvalidBundles(I, "callbrs",
-                        {LLVMContext::OB_deopt, LLVMContext::OB_funclet});
-
-  assert(I.isInlineAsm() && "Only know how to handle inlineasm callbr");
-  visitInlineAsm(I);
+  if (I.isInlineAsm()) {
+    // Deopt bundles are lowered in LowerCallSiteWithDeoptBundle, and we don't
+    // have to do anything here to lower funclet bundles.
+    failForInvalidBundles(I, "callbrs",
+                          {LLVMContext::OB_deopt, LLVMContext::OB_funclet});
----------------
nikic wrote:

Okay, I see that this is rejected by the verifier. It would help if there was an `assert(!I.hasOperandBundles() && "Can't have operand bundles")` to make this obvious.

https://github.com/llvm/llvm-project/pull/133907