Replace inline type IDs with global constants in LLVM IR

spec/compiler/codegen/union_type_spec.cr

@@ -224,9 +224,9 @@ describe "Code gen: union type" do
 
     str = mod.to_s
     {% if LibLLVM::IS_LT_150 %}
-      str.should contain("store i512 1, i512* %2, align 8")
+      str.should match(/store i512 1, i512\* %\d+, align 8/)
     {% else %}
-      str.should contain("store i512 1, ptr %1, align 8")
+      str.should match(/store i512 1, ptr %\d+, align 8/)
     {% end %}
 
     # an i512 store defaults to 16-byte alignment, which is undefined behavior

src/compiler/crystal/codegen/codegen.cr

@@ -2462,7 +2462,7 @@ module Crystal
         global.linkage = LLVM::Linkage::Private
         global.global_constant = true
         global.initializer = llvm_context.const_struct [
-          type_id(@program.string),
+          int32(@program.llvm_id.type_id(@program.string)), # in practice, should always be 1
           int32(str.bytesize),
           int32(str.size),
           llvm_context.const_string(str),

src/compiler/crystal/codegen/type_id.cr

@@ -65,6 +65,25 @@ class Crystal::CodeGenVisitor
   end
 
   private def type_id_impl(type)
-    int(@program.llvm_id.type_id(type))
+    type_id_name = "#{type.llvm_name}:type_id"
+
+    global = @main_mod.globals[type_id_name]?
+    unless global
+      global = @main_mod.globals.add(@main_llvm_context.int32, type_id_name)
+      global.linkage = LLVM::Linkage::Internal if @single_module
+      global.initializer = @main_llvm_context.int32.const_int(@program.llvm_id.type_id(type))
+      global.global_constant = true
+    end
+
+    if @llvm_mod != @main_mod
+      global = @llvm_mod.globals[type_id_name]?
+      unless global
+        global = @llvm_mod.globals.add(@llvm_context.int32, type_id_name)
+        global.linkage = LLVM::Linkage::External
+        global.global_constant = true
+      end
+    end
+
+    load(@llvm_context.int32, global)
   end
 end