[IR] Fix vector.splice verifier scaling by vscale for fixed length vectors (#170807)

Currently we multiply the known minimum number of elements by vscale
even if the vector in question is fixed, so sometimes we miss some fixed
vectors with out of bounds indices.

Author: lukel97

llvm/lib/IR/Verifier.cpp

@@ -6570,7 +6570,8 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
     VectorType *VecTy = cast<VectorType>(Call.getType());
     int64_t Idx = cast<ConstantInt>(Call.getArgOperand(2))->getSExtValue();
     int64_t KnownMinNumElements = VecTy->getElementCount().getKnownMinValue();
-    if (Call.getParent() && Call.getParent()->getParent()) {
+    if (VecTy->isScalableTy() && Call.getParent() &&
+        Call.getParent()->getParent()) {
       AttributeList Attrs = Call.getParent()->getParent()->getAttributes();
       if (Attrs.hasFnAttr(Attribute::VScaleRange))
         KnownMinNumElements *= Attrs.getFnAttrs().getVScaleRangeMin();

llvm/test/Verifier/invalid-splice.ll

@@ -26,7 +26,7 @@ define <2 x double> @splice_v2f64_idx2(<2 x double> %a, <2 x double> %b) #0 {
 
 ; CHECK: The splice index exceeds the range [-VL, VL-1] where VL is the known minimum number of elements in the vector
 define <2 x double> @splice_v2f64_idx3(<2 x double> %a, <2 x double> %b) #1 {
-  %res = call <2 x double> @llvm.vector.splice.v2f64(<2 x double> %a, <2 x double> %b, i32 4)
+  %res = call <2 x double> @llvm.vector.splice.v2f64(<2 x double> %a, <2 x double> %b, i32 3)
   ret <2 x double> %res
 }