[llvm] [TLI] replace-with-veclib works with FRem Instruction. (PR #76166)

[Maciej Gabka via llvm-commits]

================
@@ -69,88 +69,97 @@ Function *getTLIFunction(Module *M, FunctionType *VectorFTy,
   return TLIFunc;
 }
 
-/// Replace the call to the vector intrinsic ( \p CalltoReplace ) with a call to
-/// the corresponding function from the vector library ( \p TLIVecFunc ).
-static void replaceWithTLIFunction(CallInst &CalltoReplace, VFInfo &Info,
+/// Replace the instruction \p I with a call to the corresponding function from
+/// the vector library ( \p TLIVecFunc ).
+static void replaceWithTLIFunction(Instruction &I, VFInfo &Info,
                                    Function *TLIVecFunc) {
-  IRBuilder<> IRBuilder(&CalltoReplace);
-  SmallVector<Value *> Args(CalltoReplace.args());
+  IRBuilder<> IRBuilder(&I);
+  auto *CI = dyn_cast<CallInst>(&I);
+  SmallVector<Value *> Args(CI ? CI->args() : I.operands());
   if (auto OptMaskpos = Info.getParamIndexForOptionalMask()) {
-    auto *MaskTy = VectorType::get(Type::getInt1Ty(CalltoReplace.getContext()),
-                                   Info.Shape.VF);
+    auto *MaskTy =
+        VectorType::get(Type::getInt1Ty(I.getContext()), Info.Shape.VF);
     Args.insert(Args.begin() + OptMaskpos.value(),
                 Constant::getAllOnesValue(MaskTy));
   }
 
-  // Preserve the operand bundles.
+  // If it is a call instruction, preserve the operand bundles.
   SmallVector<OperandBundleDef, 1> OpBundles;
-  CalltoReplace.getOperandBundlesAsDefs(OpBundles);
-  CallInst *Replacement = IRBuilder.CreateCall(TLIVecFunc, Args, OpBundles);
-  CalltoReplace.replaceAllUsesWith(Replacement);
+  if (CI)
+    CI->getOperandBundlesAsDefs(OpBundles);
+
+  auto *Replacement = IRBuilder.CreateCall(TLIVecFunc, Args, OpBundles);
+  I.replaceAllUsesWith(Replacement);
   // Preserve fast math flags for FP math.
   if (isa<FPMathOperator>(Replacement))
-    Replacement->copyFastMathFlags(&CalltoReplace);
+    Replacement->copyFastMathFlags(&I);
 }
 
-/// Returns true when successfully replaced \p CallToReplace with a suitable
-/// function taking vector arguments, based on available mappings in the \p TLI.
-/// Currently only works when \p CallToReplace is a call to vectorized
-/// intrinsic.
+/// Returns true when successfully replaced \p I with a suitable function taking
+/// vector arguments, based on available mappings in the \p TLI. Currently only
+/// works when \p I is a call to vectorized intrinsic or the frem instruction.
 static bool replaceWithCallToVeclib(const TargetLibraryInfo &TLI,
-                                    CallInst &CallToReplace) {
-  if (!CallToReplace.getCalledFunction())
-    return false;
-
-  auto IntrinsicID = CallToReplace.getCalledFunction()->getIntrinsicID();
-  // Replacement is only performed for intrinsic functions.
-  if (IntrinsicID == Intrinsic::not_intrinsic)
-    return false;
-
-  // Compute arguments types of the corresponding scalar call. Additionally
-  // checks if in the vector call, all vector operands have the same EC.
-  ElementCount VF = ElementCount::getFixed(0);
-  SmallVector<Type *> ScalarArgTypes;
-  for (auto Arg : enumerate(CallToReplace.args())) {
-    auto *ArgTy = Arg.value()->getType();
-    if (isVectorIntrinsicWithScalarOpAtArg(IntrinsicID, Arg.index())) {
-      ScalarArgTypes.push_back(ArgTy);
-    } else if (auto *VectorArgTy = dyn_cast<VectorType>(ArgTy)) {
-      ScalarArgTypes.push_back(ArgTy->getScalarType());
-      // Disallow vector arguments with different VFs. When processing the first
-      // vector argument, store it's VF, and for the rest ensure that they match
-      // it.
-      if (VF.isZero())
-        VF = VectorArgTy->getElementCount();
-      else if (VF != VectorArgTy->getElementCount())
+                                    Instruction &I) {
+  std::string ScalarName;
+  ElementCount EC = ElementCount::getFixed(0);
+  Function *FuncToReplace = nullptr;
+  SmallVector<Type *, 8> ScalarArgTypes;
+  // Compute the argument types of the corresponding scalar call, the scalar
+  // function name, and EC. For calls, it additionally checks if in the vector
+  // call, all vector operands have the same EC.
+  if (auto *CI = dyn_cast<CallInst>(&I)) {
+    Intrinsic::ID IID = CI->getCalledFunction()->getIntrinsicID();
+    assert(IID != Intrinsic::not_intrinsic && "Not an intrinsic");
+    FuncToReplace = CI->getCalledFunction();
+    for (auto Arg : enumerate(CI->args())) {
+      auto *ArgTy = Arg.value()->getType();
+      if (isVectorIntrinsicWithScalarOpAtArg(IID, Arg.index())) {
+        ScalarArgTypes.push_back(ArgTy);
+      } else if (auto *VectorArgTy = dyn_cast<VectorType>(ArgTy)) {
+        ScalarArgTypes.push_back(VectorArgTy->getElementType());
+        // Disallow vector arguments with different VFs. When processing the
+        // first vector argument, store it's VF, and for the rest ensure that
+        // they match it.
+        if (EC.isZero())
+          EC = VectorArgTy->getElementCount();
+        else if (EC != VectorArgTy->getElementCount())
+          return false;
+      } else
+        // Exit when it is supposed to be a vector argument but it isn't.
         return false;
-    } else
-      // Exit when it is supposed to be a vector argument but it isn't.
+    }
+    // Try to reconstruct the name for the scalar version of the instruction,
+    // using scalar argument types.
+    ScalarName = Intrinsic::isOverloaded(IID)
+                     ? Intrinsic::getName(IID, ScalarArgTypes, I.getModule())
+                     : Intrinsic::getName(IID).str();
+  } else {
+    assert(I.getType()->isVectorTy() && "Instruction must use vectors");
+    LibFunc Func;
+    auto *ScalarTy = I.getType()->getScalarType();
+    if (!TLI.getLibFunc(I.getOpcode(), ScalarTy, Func))
       return false;
+    ScalarName = TLI.getName(Func);
+    ScalarArgTypes = {ScalarTy, ScalarTy};
+    if (auto *VTy = dyn_cast<VectorType>(I.getType()))
----------------
mgabka wrote:

to me it feels like this could be done before the assert, i.e:

auto *VTy = dyn_cast<VectorType>(I.getType()
assert(VTy  && "Instruction must use vectors");
and then you can use everywhere VTy instead calling several times getType.

and it will also remove the confusing " if (auto *VTy = dyn_cast<VectorType>(I.getType()))" without else, which in theory should never happen as the  isSupportedInstruction ensures that we only get here with vector version of frem.

https://github.com/llvm/llvm-project/pull/76166