[clang] [llvm] Reimplement constrained 'trunc' using operand bundles (PR #118253)

[Kevin P. Neal via llvm-commits]

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@@ -86,6 +86,43 @@ IRBuilderBase::createCallHelper(Function *Callee, ArrayRef<Value *> Ops,
   return CI;
 }
 
+CallInst *IRBuilderBase::CreateCall(FunctionType *FTy, Value *Callee,
+                                    ArrayRef<Value *> Args,
+                                    ArrayRef<OperandBundleDef> OpBundles,
+                                    const Twine &Name, MDNode *FPMathTag) {
+  ArrayRef<OperandBundleDef> ActualBundlesRef = OpBundles;
+  SmallVector<OperandBundleDef, 2> ActualBundles;
+
+  if (IsFPConstrained) {
+    if (const auto *Func = dyn_cast<Function>(Callee)) {
+      if (Intrinsic::ID ID = Func->getIntrinsicID()) {
+        if (IntrinsicInst::canAccessFPEnvironment(ID)) {
+          bool NeedRound = true, NeedExcept = true;
+          for (const auto &Item : OpBundles) {
+            if (NeedRound && Item.getTag() == "fpe.round")
+              NeedRound = false;
+            else if (NeedExcept && Item.getTag() == "fpe.except")
+              NeedExcept = false;
+            ActualBundles.push_back(Item);
----------------
kpneal wrote:

Do we want intrinsics where the rounding mode is baked in (like trunc or floor) to be allowed to have a rounding mode bundle? Or, do we want the rounding mode bundle to be able to specify a rounding mode that isn't the one baked into the intrinsic? I'm leaning towards the rounding mode bundle not being allowed.

https://github.com/llvm/llvm-project/pull/118253