SPV: Correct selection of storage-image capabilities. Fixes #986.

Code was reflecting an old historical use of sampled as a SPIR-V
2-valued operand, instead of its current 3 values.

SPIRV/SpvBuilder.cpp

@@ -402,6 +402,8 @@ Id Builder::makeFunctionType(Id returnType, const std::vector<Id>& paramTypes)
 
 Id Builder::makeImageType(Id sampledType, Dim dim, bool depth, bool arrayed, bool ms, unsigned sampled, ImageFormat format)
 {
+    assert(sampled == 1 || sampled == 2);
+
     // try to find it
     Instruction* type;
     for (int t = 0; t < (int)groupedTypes[OpTypeImage].size(); ++t) {
@@ -433,27 +435,27 @@ Id Builder::makeImageType(Id sampledType, Dim dim, bool depth, bool arrayed, boo
     // deal with capabilities
     switch (dim) {
     case DimBuffer:
-        if (sampled)
+        if (sampled == 1)
             addCapability(CapabilitySampledBuffer);
         else
             addCapability(CapabilityImageBuffer);
         break;
     case Dim1D:
-        if (sampled)
+        if (sampled == 1)
             addCapability(CapabilitySampled1D);
         else
             addCapability(CapabilityImage1D);
         break;
     case DimCube:
         if (arrayed) {
-            if (sampled)
+            if (sampled == 1)
                 addCapability(CapabilitySampledCubeArray);
             else
                 addCapability(CapabilityImageCubeArray);
         }
         break;
     case DimRect:
-        if (sampled)
+        if (sampled == 1)
             addCapability(CapabilitySampledRect);
         else
             addCapability(CapabilityImageRect);
@@ -466,10 +468,11 @@ Id Builder::makeImageType(Id sampledType, Dim dim, bool depth, bool arrayed, boo
     }
 
     if (ms) {
-        if (arrayed)
-            addCapability(CapabilityImageMSArray);
-        if (! sampled)
+        if (sampled == 2) {
             addCapability(CapabilityStorageImageMultisample);
+            if (arrayed)
+                addCapability(CapabilityImageMSArray);
+        }
     }
 
     return type->getResultId();