[SVE] Fix wrong usage of getNumElements() in matchIntrinsicType

I have changed the ScalableVecArgument case in matchIntrinsicType
to create a new FixedVectorType. This means that the next case we
hit (Vector) will not assert when calling getNumElements(), since
we know that it's always a FixedVectorType. This is a temporary
measure for now, and it will be fixed properly in another patch
that refactors this code.

The changes are covered by this existing test:

CodeGen/AArch64/sve-intrinsics-fp-converts.ll

In addition, I have added a new test to ensure that we correctly
reject SVE intrinsics when called with fixed length vector types.

Differential Revision: https://reviews.llvm.org/D79416

Author: david-arm

Diff for: llvm/lib/IR/Function.cpp

@@ -1180,7 +1180,9 @@ static bool matchIntrinsicType(
     case IITDescriptor::Quad: return !Ty->isFP128Ty();
     case IITDescriptor::Integer: return !Ty->isIntegerTy(D.Integer_Width);
     case IITDescriptor::Vector: {
-      VectorType *VT = dyn_cast<VectorType>(Ty);
+      // FIXME: We shouldn't be assuming all Vector types are fixed width.
+      // This will be fixed soon in another future patch.
+      FixedVectorType *VT = dyn_cast<FixedVectorType>(Ty);
       return !VT || VT->getNumElements() != D.Vector_Width ||
              matchIntrinsicType(VT->getElementType(), Infos, ArgTys,
                                 DeferredChecks, IsDeferredCheck);
@@ -1357,7 +1359,11 @@ static bool matchIntrinsicType(
     case IITDescriptor::ScalableVecArgument: {
       if (!isa<ScalableVectorType>(Ty))
         return true;
-      return matchIntrinsicType(Ty, Infos, ArgTys, DeferredChecks,
+      ScalableVectorType *STy = cast<ScalableVectorType>(Ty);
+      unsigned MinElts = STy->getMinNumElements();
+      FixedVectorType *FVTy =
+          FixedVectorType::get(STy->getElementType(), MinElts);
+      return matchIntrinsicType(FVTy, Infos, ArgTys, DeferredChecks,
                                 IsDeferredCheck);
     }
     case IITDescriptor::VecOfBitcastsToInt: {

Diff for: llvm/test/CodeGen/AArch64/sve-bad-intrinsics.ll

@@ -0,0 +1,17 @@
+; RUN: not llc -mtriple=aarch64-linux-gnu -mattr=+sve < %s 2>%t
+; RUN: FileCheck --check-prefix=CHECK-ERROR %s <%t
+
+declare <4 x float> @llvm.arm.neon.vcvthf2fp(<vscale x 4 x i16>)
+declare <vscale x 4 x i16> @llvm.arm.neon.vcvtfp2hf(<vscale x 4 x float>)
+
+; CHECK-ERROR: Intrinsic has incorrect return type!
+define <vscale x 4 x i16> @bad1() {
+  %r = call <vscale x 4 x i16> @llvm.arm.neon.vcvtfp2hf(<vscale x 4 x float> zeroinitializer)
+  ret <vscale x 4 x i16> %r
+}
+
+; CHECK-ERROR: Intrinsic has incorrect argument type!
+define <4 x float> @bad2() {
+  %r = call <4 x float> @llvm.arm.neon.vcvthf2fp(<vscale x 4 x i16> zeroinitializer)
+  ret <4 x float> %r
+}