Linkage type fix for global variables translation (#1148)

This is a workaround to fix translation of linkage type of "llvm.used" and
"llvm.compiler.used" global variables that should be "appending" instead of
"export".

Author: KornevNikita

lib/SPIRV/SPIRVReader.cpp

@@ -4143,6 +4143,9 @@ bool SPIRVToLLVM::transSourceExtension() {
 
 llvm::GlobalValue::LinkageTypes
 SPIRVToLLVM::transLinkageType(const SPIRVValue *V) {
+  std::string ValueName = V->getName();
+  if (ValueName == "llvm.used" || ValueName == "llvm.compiler.used")
+    return GlobalValue::AppendingLinkage;
   int LT = V->getLinkageType();
   switch (LT) {
   case internal::LinkageTypeInternal:

test/appending-linkage-type.ll

@@ -0,0 +1,33 @@
+; RUN: llvm-as < %s -o %t.bc
+; RUN: llvm-spirv %t.bc -o %t.spv -spirv-ext=+SPV_INTEL_vector_compute,+SPV_INTEL_usm_storage_classes
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis %t.rev.bc -o %t.rev.ll
+; RUN: FileCheck %s --input-file %t.rev.ll --check-prefix CHECK-LLVM
+
+; ModuleID = 'appending-linkage-type'
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v24:32:32-v32:32:32-v48:64:64-v64:64:64-v96:128:128-v128:128:128-v192:256:256-v256:256:256-v512:512:512-v1024:1024:1024"
+target triple = "spir64-unknown-unknown"
+
+%union.int_double = type { i64 }
+
+@_c0 = internal addrspace(1) constant %union.int_double { i64 4607182418800017408 }, align 8 #0
+@._c0.ref = internal constant %union.int_double addrspace(1)* @_c0 #0
+; CHECK-LLVM: @llvm.compiler.used = appending global
+@llvm.compiler.used = appending global [1 x i8*] [i8* bitcast (%union.int_double addrspace(1)** @._c0.ref to i8*)] #0
+
+attributes #0 = { "VCGlobalVariable" }
+
+!spirv.MemoryModel = !{!0}
+!opencl.enable.FP_CONTRACT = !{}
+!spirv.Source = !{!1}
+!opencl.spir.version = !{!2}
+!opencl.ocl.version = !{!1}
+!opencl.used.extensions = !{!3}
+!opencl.used.optional.core.features = !{!3}
+!spirv.Generator = !{!4}
+
+!0 = !{i32 2, i32 2}
+!1 = !{i32 0, i32 0}
+!2 = !{i32 1, i32 2}
+!3 = !{}
+!4 = !{i16 6, i16 14}