Move widenable branch formation into makeGuardControlFlowExplicit helper

This is mostly NFC, but I removed the setting of the guard's calling convention onto the WC call.  Why?  Because it was untested, and was producing an ill defined output as the declaration's convention wasn't been changed leaving a mismatch which is UB.

llvm/include/llvm/Transforms/Utils/GuardUtils.h

@@ -23,8 +23,11 @@ class Value;
 /// by the condition of guard's first argument. The taken branch then goes to
 /// the block that contains  \p Guard's successors, and the non-taken branch
 /// goes to a newly-created deopt block that contains a sole call of the
-/// deoptimize function \p DeoptIntrinsic.
-void makeGuardControlFlowExplicit(Function *DeoptIntrinsic, CallInst *Guard);
+/// deoptimize function \p DeoptIntrinsic.  If 'UseWC' is set, preserve the
+/// widenable nature of the guard by lowering to equivelent form.  If not set,
+/// lower to a form without widenable semantics.
+void makeGuardControlFlowExplicit(Function *DeoptIntrinsic, CallInst *Guard,
+                                  bool UseWC);
 
 /// Given a branch we know is widenable (defined per Analysis/GuardUtils.h),
 /// widen it such that condition 'NewCond' is also known to hold on the taken

llvm/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp

@@ -61,7 +61,7 @@ static bool lowerGuardIntrinsic(Function &F) {
   DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv());
 
   for (auto *CI : ToLower) {
-    makeGuardControlFlowExplicit(DeoptIntrinsic, CI);
+    makeGuardControlFlowExplicit(DeoptIntrinsic, CI, false);
     CI->eraseFromParent();
   }
 

llvm/lib/Transforms/Scalar/MakeGuardsExplicit.cpp

@@ -58,22 +58,9 @@ struct MakeGuardsExplicitLegacyPass : public FunctionPass {
 static void turnToExplicitForm(CallInst *Guard, Function *DeoptIntrinsic) {
   // Replace the guard with an explicit branch (just like in GuardWidening).
   BasicBlock *BB = Guard->getParent();
-  makeGuardControlFlowExplicit(DeoptIntrinsic, Guard);
-  BranchInst *ExplicitGuard = cast<BranchInst>(BB->getTerminator());
-  assert(ExplicitGuard->isConditional() && "Must be!");
+  makeGuardControlFlowExplicit(DeoptIntrinsic, Guard, true);
+  assert(isWidenableBranch(BB->getTerminator()) && "should hold");
 
-  // We want the guard to be expressed as explicit control flow, but still be
-  // widenable. For that, we add Widenable Condition intrinsic call to the
-  // guard's condition.
-  IRBuilder<> B(ExplicitGuard);
-  auto *WidenableCondition =
-      B.CreateIntrinsic(Intrinsic::experimental_widenable_condition,
-                        {}, {}, nullptr, "widenable_cond");
-  WidenableCondition->setCallingConv(Guard->getCallingConv());
-  auto *NewCond =
-      B.CreateAnd(ExplicitGuard->getCondition(), WidenableCondition);
-  NewCond->setName("exiplicit_guard_cond");
-  ExplicitGuard->setCondition(NewCond);
   Guard->eraseFromParent();
 }
 

llvm/lib/Transforms/Utils/GuardUtils.cpp

@@ -26,7 +26,7 @@ static cl::opt<uint32_t> PredicatePassBranchWeight(
              "reciprocal of this value (default = 1 << 20)"));
 
 void llvm::makeGuardControlFlowExplicit(Function *DeoptIntrinsic,
-                                        CallInst *Guard) {
+                                        CallInst *Guard, bool UseWC) {
   OperandBundleDef DeoptOB(*Guard->getOperandBundle(LLVMContext::OB_deopt));
   SmallVector<Value *, 4> Args(std::next(Guard->arg_begin()), Guard->arg_end());
 
@@ -62,6 +62,18 @@ void llvm::makeGuardControlFlowExplicit(Function *DeoptIntrinsic,
 
   DeoptCall->setCallingConv(Guard->getCallingConv());
   DeoptBlockTerm->eraseFromParent();
+
+  if (UseWC) {
+    // We want the guard to be expressed as explicit control flow, but still be
+    // widenable. For that, we add Widenable Condition intrinsic call to the
+    // guard's condition.
+    IRBuilder<> B(CheckBI);
+    auto *WC = B.CreateIntrinsic(Intrinsic::experimental_widenable_condition,
+                                 {}, {}, nullptr, "widenable_cond");
+    CheckBI->setCondition(B.CreateAnd(CheckBI->getCondition(), WC,
+                                      "exiplicit_guard_cond"));
+    assert(isWidenableBranch(CheckBI) && "sanity check");
+  }
 }