[RISCV] Add assertions to VSETVLIInfo accessors. NFC (#169462)

Author: topperc

llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp

@@ -607,12 +607,36 @@ class VSETVLIInfo {
     }
   }
 
-  unsigned getSEW() const { return SEW; }
-  RISCVVType::VLMUL getVLMUL() const { return VLMul; }
-  bool getTailAgnostic() const { return TailAgnostic; }
-  bool getMaskAgnostic() const { return MaskAgnostic; }
-  bool getAltFmt() const { return AltFmt; }
-  unsigned getTWiden() const { return TWiden; }
+  unsigned getSEW() const {
+    assert(isValid() && !isUnknown() &&
+           "Can't use VTYPE for uninitialized or unknown");
+    return SEW;
+  }
+  RISCVVType::VLMUL getVLMUL() const {
+    assert(isValid() && !isUnknown() &&
+           "Can't use VTYPE for uninitialized or unknown");
+    return VLMul;
+  }
+  bool getTailAgnostic() const {
+    assert(isValid() && !isUnknown() &&
+           "Can't use VTYPE for uninitialized or unknown");
+    return TailAgnostic;
+  }
+  bool getMaskAgnostic() const {
+    assert(isValid() && !isUnknown() &&
+           "Can't use VTYPE for uninitialized or unknown");
+    return MaskAgnostic;
+  }
+  bool getAltFmt() const {
+    assert(isValid() && !isUnknown() &&
+           "Can't use VTYPE for uninitialized or unknown");
+    return AltFmt;
+  }
+  unsigned getTWiden() const {
+    assert(isValid() && !isUnknown() &&
+           "Can't use VTYPE for uninitialized or unknown");
+    return TWiden;
+  }
 
   bool hasNonZeroAVL(const LiveIntervals *LIS) const {
     if (hasAVLImm())