Add support for OpUndef

Treat OpUndef identically to OpConstantNull for now.

Change-Id: I721f2bf5e053d6a8d6f563272b1d44b6636a157c
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27529
Tested-by: Chris Forbes <[email protected]>
Presubmit-Ready: Chris Forbes <[email protected]>
Reviewed-by: Ben Clayton <[email protected]>

Author: chrisforbes

src/Pipeline/SpirvShader.cpp

@@ -215,7 +215,9 @@ namespace sw
 				CreateConstant(insn).constantValue[0] = ~0u;	// represent boolean true as all bits set
 				break;
 			case spv::OpConstantNull:
+			case spv::OpUndef:
 			{
+				// TODO: consider a real LLVM-level undef. For now, zero is a perfectly good value.
 				// OpConstantNull forms a constant of arbitrary type, all zeros.
 				auto &object = CreateConstant(insn);
 				auto &objectTy = getType(object.type);
@@ -1062,6 +1064,7 @@ namespace sw
 		case spv::OpConstantTrue:
 		case spv::OpConstantFalse:
 		case spv::OpConstantComposite:
+		case spv::OpUndef:
 		case spv::OpExtension:
 		case spv::OpCapability:
 		case spv::OpEntryPoint: