diff --git a/lib/HLSL/DxilPackSignatureElement.cpp b/lib/HLSL/DxilPackSignatureElement.cpp
index 3f6b0ce300..0337c4c28f 100644
--- a/lib/HLSL/DxilPackSignatureElement.cpp
+++ b/lib/HLSL/DxilPackSignatureElement.cpp
@@ -73,8 +73,10 @@ unsigned PackDxilSignature(DxilSignature &sig, DXIL::PackingStrategy packing) {
     // incrementally assign each element that belongs in the signature to the
     // start of the next free row
     for (auto &SE : packElements) {
-      SE.SetLocation(rowsUsed, 0);
-      rowsUsed += SE.GetRows();
+      if (SE.GetRows() <= (32 - rowsUsed)) {
+        SE.SetLocation(rowsUsed, 0);
+        rowsUsed += SE.GetRows();
+      }
     }
     break;
 
diff --git a/lib/HLSL/HLSignatureLower.cpp b/lib/HLSL/HLSignatureLower.cpp
index bb5c25f6ee..3e03d7725e 100644
--- a/lib/HLSL/HLSignatureLower.cpp
+++ b/lib/HLSL/HLSignatureLower.cpp
@@ -37,8 +37,7 @@ namespace {
 // Return semantic index.
 unsigned UpdateSemanticAndInterpMode(StringRef &semName,
                                      DXIL::InterpolationMode &mode,
-                                     DXIL::SigPointKind kind,
-                                     LLVMContext &Context) {
+                                     DXIL::SigPointKind kind, Function *Entry) {
   llvm::StringRef baseSemName; // The 'FOO' in 'FOO1'.
   uint32_t semIndex;           // The '1' in 'FOO1'
 
@@ -61,7 +60,9 @@ unsigned UpdateSemanticAndInterpMode(StringRef &semName,
     case InterpolationMode::Kind::Constant:
     case InterpolationMode::Kind::Undefined:
     case InterpolationMode::Kind::Invalid: {
-      llvm_unreachable("invalid interpolation mode for SV_Position");
+      dxilutil::EmitErrorOnFunction(
+          Entry->getContext(), Entry,
+          "invalid interpolation mode for SV_Position");
     } break;
     case InterpolationMode::Kind::LinearNoperspective:
     case InterpolationMode::Kind::LinearNoperspectiveCentroid:
@@ -80,7 +81,7 @@ DxilSignatureElement *FindArgInSignature(Argument &arg,
                                          DxilSignature &sig) {
   // Match output ID.
   unsigned semIndex =
-      UpdateSemanticAndInterpMode(semantic, interpMode, kind, arg.getContext());
+      UpdateSemanticAndInterpMode(semantic, interpMode, kind, arg.getParent());
 
   for (uint32_t i = 0; i < sig.GetElements().size(); i++) {
     DxilSignatureElement &SE = sig.GetElement(i);
@@ -290,7 +291,7 @@ void HLSignatureLower::ProcessArgument(Function *func,
     return;
   }
   UpdateSemanticAndInterpMode(semanticStr, interpMode, sigPoint->GetKind(),
-                              arg.getContext());
+                              func);
 
   // Get Semantic interpretation, skipping if not in signature
   const Semantic *pSemantic = Semantic::GetByName(semanticStr);
@@ -519,15 +520,17 @@ void HLSignatureLower::AllocateDxilInputOutputs() {
 
   hlsl::PackDxilSignature(EntrySig.InputSignature, packing);
   if (!EntrySig.InputSignature.IsFullyAllocated()) {
-    llvm_unreachable(
+    dxilutil::EmitErrorOnFunction(
+        Entry->getContext(), Entry,
         "Failed to allocate all input signature elements in available space.");
   }
 
   if (props.shaderKind != DXIL::ShaderKind::Amplification) {
     hlsl::PackDxilSignature(EntrySig.OutputSignature, packing);
     if (!EntrySig.OutputSignature.IsFullyAllocated()) {
-      llvm_unreachable("Failed to allocate all output signature elements in "
-                       "available space.");
+      dxilutil::EmitErrorOnFunction(Entry->getContext(), Entry,
+                                    "Failed to allocate all output signature "
+                                    "elements in available space.");
     }
   }
 
@@ -536,8 +539,9 @@ void HLSignatureLower::AllocateDxilInputOutputs() {
       props.shaderKind == DXIL::ShaderKind::Mesh) {
     hlsl::PackDxilSignature(EntrySig.PatchConstOrPrimSignature, packing);
     if (!EntrySig.PatchConstOrPrimSignature.IsFullyAllocated()) {
-      llvm_unreachable("Failed to allocate all patch constant signature "
-                       "elements in available space.");
+      dxilutil::EmitErrorOnFunction(Entry->getContext(), Entry,
+                                    "Failed to allocate all patch constant "
+                                    "signature elements in available space.");
     }
   }
 }
diff --git a/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/ia_sig_too_large.hlsl b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/ia_sig_too_large.hlsl
new file mode 100644
index 0000000000..fdb10a19da
--- /dev/null
+++ b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/ia_sig_too_large.hlsl
@@ -0,0 +1,14 @@
+// RUN: %dxc -E main -T vs_6_0 %s | FileCheck %s
+
+// Expect error when the Input Assembler (vertex input) signature is too large
+// CHECK: error: Failed to allocate all input signature elements in available space.
+
+struct VSIN {
+    float4 pos : Position;
+    float array1[30] : ARRAY1;
+    float array2[2] : ARRAY2;
+};
+
+float4 main(VSIN In) : SV_Position {
+    return In.pos;
+}
diff --git a/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/invalid_interpolation_sv_position.hlsl b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/invalid_interpolation_sv_position.hlsl
new file mode 100644
index 0000000000..e9ab3558cd
--- /dev/null
+++ b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/invalid_interpolation_sv_position.hlsl
@@ -0,0 +1,11 @@
+// RUN: %dxc -E main -T ps_6_0 %s | FileCheck %s
+
+// CHECK: error: invalid interpolation mode for SV_Position
+
+struct PSIN {
+    nointerpolation float4 pos : SV_Position;
+};
+
+float main(PSIN In) : SV_Target{
+    return In.pos.x;
+}
diff --git a/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/output_sig_too_large.hlsl b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/output_sig_too_large.hlsl
new file mode 100644
index 0000000000..1541621180
--- /dev/null
+++ b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/output_sig_too_large.hlsl
@@ -0,0 +1,15 @@
+// RUN: %dxc -E main -T vs_6_0 %s | FileCheck %s
+
+// Expect error when the output signature is too large
+// CHECK: error: Failed to allocate all output signature elements in available space.
+
+struct VSOUT {
+    float4 pos : SV_Position;
+    float4 array1[30] : BIGARRAY;
+    float4 array2[2] : SMALLARRAY;
+};
+
+VSOUT main() {
+    VSOUT Out = (VSOUT)0;
+    return Out;
+}
diff --git a/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/pc_sig_too_large.hlsl b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/pc_sig_too_large.hlsl
new file mode 100644
index 0000000000..944fe7a380
--- /dev/null
+++ b/tools/clang/test/HLSLFileCheck/hlsl/diagnostics/errors/pc_sig_too_large.hlsl
@@ -0,0 +1,39 @@
+// RUN: %dxc -E main -T hs_6_0 %s | FileCheck %s
+
+// Expect error when the patch constant signature is too large
+// CHECK: error: Failed to allocate all patch constant signature elements in available space.
+
+#define NumOutPoints 2
+
+struct HsCpIn {
+    float4 pos : SV_Position;
+};
+
+struct HsCpOut {
+    float4 pos : SV_Position;
+};
+
+struct HsPcfOut
+{
+  float tessOuter[4] : SV_TessFactor;
+  float tessInner[2] : SV_InsideTessFactor;
+  float4 array1[25] : BIGARRAY;
+  float4 array2[2] : SMALLARRAY;
+};
+
+HsPcfOut pcf(InputPatch<HsCpIn, NumOutPoints> patch, uint patchId : SV_PrimitiveID) {
+  HsPcfOut output = (HsPcfOut)0;
+  return output;
+}
+
+[patchconstantfunc("pcf")]
+[domain("quad")]
+[partitioning("fractional_odd")]
+[outputtopology("triangle_ccw")]
+[outputcontrolpoints(NumOutPoints)]
+HsCpOut main(InputPatch<HsCpIn, NumOutPoints> patch,
+             uint cpId : SV_OutputControlPointID,
+             uint patchId : SV_PrimitiveID) {
+    HsCpOut output = (HsCpOut)0;
+    return output;
+}