Set WordCount for SPIRVVariable correctly (#2437)

SPIRVVariable should have a WordCount of 4 + 1 (if optional Initializer is added).
Set WordCount to 4 if Initializer is not added.

Signed-off-by: Lu, John <[email protected]>

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@274e918b508c993

Author: LU-JOHN

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVInstruction.h

@@ -443,8 +443,8 @@ class SPIRVVariable : public SPIRVInstruction {
                 const std::string &TheName,
                 SPIRVStorageClassKind TheStorageClass, SPIRVBasicBlock *TheBB,
                 SPIRVModule *TheM)
-      : SPIRVInstruction(TheInitializer ? 5 : 4, OpVariable, TheType, TheId,
-                         TheBB, TheM),
+      : SPIRVInstruction(TheInitializer && !TheInitializer->isUndef() ? 5 : 4,
+                         OpVariable, TheType, TheId, TheBB, TheM),
         StorageClass(TheStorageClass) {
     if (TheInitializer && !TheInitializer->isUndef())
       Initializer.push_back(TheInitializer->getId());

llvm-spirv/test/var_undef.ll

@@ -0,0 +1,28 @@
+; Ensure that encoding of variable with undef initializer
+; has correct wordcount
+
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc -o %t.spv
+; RUN: llvm-spirv -to-text %t.spv -o %t.spt
+; RUN: FileCheck < %t.spt %s --check-prefix CHECK-SPIRV
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis %t.rev.bc -o %t.rev.ll
+; RUN: FileCheck < %t.rev.ll %s --check-prefix CHECK-LLVM
+
+; CHECK-SPIRV:Name [[BAR_VAR:[0-9]+]] "bar"
+;; bar variable does not have optional initializer
+;; word count must be 4
+; CHECK-SPIRV:4 Variable [[#]] [[BAR_VAR]]
+
+; CHECK-LLVM:@bar = internal addrspace(3) global %range undef, align 8
+
+target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"
+target triple = "spir64-unknown-unknown"
+
+%anon = type { %range }
+%range = type { %array }
+%array = type { [2 x i64] }
+
+@foo = internal addrspace(3) global %anon undef, align 8
+
+@bar = internal unnamed_addr addrspace(3) global %range undef, align 8