Test behavior of common global variables (#2306)

Add tests to ensure that:

A common global without addrspace is reported as an error
A common addrspace global is not transformed to a locally allocated variable
Updated error message from "can not" to "cannot". Otherwise this is a NFC.

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

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@8c357de

Author: LU-JOHN

llvm-spirv/lib/SPIRV/SPIRVWriter.cpp

@@ -2005,7 +2005,7 @@ LLVMToSPIRVBase::transValueWithoutDecoration(Value *V, SPIRVBasicBlock *BB,
       StorageClass = SPIRSPIRVAddrSpaceMap::map(AddressSpace);
       if (StorageClass == StorageClassFunction) {
         std::stringstream SS;
-        SS << "Global variable can not have Function storage class. "
+        SS << "Global variable cannot have Function storage class. "
            << "Consider setting a proper address space.\n "
            << "Original LLVM value:\n"
            << toString(GV);

llvm-spirv/test/negative/CommonGlobalVarNoAddrspace.ll

@@ -0,0 +1,24 @@
+; Ensure "common global" with no addrspace is reported as an error
+; since the SPIR-V spec states:
+;
+;   global variable declarations must always have an address space
+;   specified and that address space cannot be `0`
+
+; RUN: llvm-as %s -o %t.bc
+; RUN: not llvm-spirv %t.bc 2>&1 \
+; RUN: | FileCheck %s --check-prefix=CHECK-ERROR
+
+; CHECK-ERROR: InvalidInstruction: Can't translate llvm instruction:
+; CHECK-ERROR-NEXT: Global variable cannot have Function storage class. Consider setting a proper address space.
+; CHECK-ERROR-NEXT: Original LLVM value:
+; CHECK-ERROR-NEXT: @CG = common global i32 0, align 4
+
+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"
+
+@CG = common global i32 0, align 4
+ 
+define i32 @f() #0 {
+ %1 = load i32, i32* @CG, align 4
+ ret i32 %1
+}

llvm-spirv/test/GlobalVarNoAddrspace.ll renamed to llvm-spirv/test/negative/GlobalVarNoAddrspace.ll

@@ -1,9 +1,17 @@
+; Ensure "global" with no addrspace is reported as an error
+; since the SPIR-V spec states:
+;
+;   global variable declarations must always have an address space
+;   specified and that address space cannot be `0`
+
 ; RUN: llvm-as %s -o %t.bc
 ; RUN: not llvm-spirv %t.bc 2>&1 \
 ; RUN: | FileCheck %s --check-prefix=CHECK-ERROR
 
 ; CHECK-ERROR: InvalidInstruction: Can't translate llvm instruction:
-; CHECK-ERROR-NEXT: Global variable can not have Function storage class. Consider setting a proper address space.
+; CHECK-ERROR-NEXT: Global variable cannot have Function storage class. Consider setting a proper address space.
+; CHECK-ERROR-NEXT: Original LLVM value:
+; CHECK-ERROR-NEXT: @G = global i1 true
 
 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"

llvm-spirv/test/transcoding/CommonAddrspaceGlobalVar.ll

@@ -0,0 +1,20 @@
+; Ensure that a "common global" is not converted to a locally allocated
+; variable when translated to SPIR-V and back to LLVM.
+
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc -o %t.spv
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis < %t.rev.bc | FileCheck %s --check-prefix=CHECK-LLVM
+
+; CHECK-LLVM-NOT: alloca
+; CHECK-LLVM: @CAG = common addrspace(1) global i32 0, align 4
+; CHECK-LLVM-NOT: alloca
+
+target triple = "spir64-unknown-unknown"
+
+@CAG = common addrspace(1) global i32 0, align 4
+  
+define i32 @f() #0 {
+ %1 = load i32, i32 addrspace(1) * @CAG, align 4
+ ret i32 %1
+}