Introduce at-dispose to replace do-block constructors. (#309)

Author: maleadt

examples/Kaleidoscope/codegen.jl

@@ -23,7 +23,7 @@ Base.show(io::IO, cg::CodeGen) = print(io, "CodeGen")
 
 function create_entry_block_allocation(cg::CodeGen, fn::LLVM.Function, varname::String)
     local alloc
-    LLVM.Builder(cg.ctx) do builder
+    LLVM.@dispose builder=LLVM.Builder(cg.ctx) begin
         # Set the builder at the start of the function
         entry_block = LLVM.entry(fn)
         if isempty(LLVM.instructions(entry_block))

examples/Kaleidoscope/run.jl

@@ -16,7 +16,7 @@ function generate_IR(str; ctx::LLVM.Context)
 end
 
 function optimize!(mod::LLVM.Module)
-    LLVM.ModulePassManager() do pass_manager
+    LLVM.@dispose pass_manager=LLVM.ModulePassManager() begin
         LLVM.instruction_combining!(pass_manager)
         LLVM.reassociate!(pass_manager)
         LLVM.gvn!(pass_manager)
@@ -29,7 +29,7 @@ end
 
 function run(mod::LLVM.Module, entry::String)
     res_jl = 0.0
-    LLVM.JIT(mod) do engine
+    LLVM.@dispose engine=LLVM.JIT(mod) begin
         if !haskey(LLVM.functions(engine), entry)
             error("did not find entry function '$entry' in module")
         end
@@ -44,7 +44,7 @@ end
 function write_objectfile(mod::LLVM.Module, path::String)
     host_triple = Sys.MACHINE # LLVM.triple() might be wrong (see LLVM.jl#108)
     host_t = LLVM.Target(triple=host_triple)
-    LLVM.TargetMachine(host_t, host_triple) do tm
+    LLVM.@dispose tm=LLVM.TargetMachine(host_t, host_triple) begin
         LLVM.emit(tm, mod, LLVM.API.LLVMObjectFile, path)
     end
 end

examples/constrained.jl

@@ -33,7 +33,7 @@ meta(::Type{FPExceptStrict}) = "fpexcept.strict"
                                {F, round, fpexcept, T<:AbstractFloat, N}
     @assert N >= 0
 
-    Context() do ctx
+    @dispose ctx=Context() begin
         typ = convert(LLVMType, T; ctx)
 
         # create a function
@@ -50,7 +50,7 @@ meta(::Type{FPExceptStrict}) = "fpexcept.strict"
                                 intrinsic_typ)
 
         # generate IR
-        Builder(ctx) do builder
+        @dispose builder=Builder(ctx) begin
             entry = BasicBlock(llvm_f, "entry"; ctx)
             position!(builder, entry)
             val = call!(builder, intrinsic,

examples/generated.jl

@@ -9,7 +9,7 @@ struct CustomPtr{T}
 end
 
 @generated function Base.unsafe_load(p::CustomPtr{T}, i::Integer=1) where T
-    Context() do ctx
+    @dispose ctx=Context() begin
         # get the element type
         eltyp = convert(LLVMType, T; ctx)
 
@@ -21,7 +21,7 @@ end
         llvmf, _ = create_function(eltyp, paramtyps)
 
         # generate IR
-        Builder(ctx) do builder
+        @dispose builder=Builder(ctx) begin
             entry = BasicBlock(llvmf, "entry"; ctx)
             position!(builder, entry)
 

examples/sum.jl

@@ -11,7 +11,7 @@ else
     y = Int32(2)
 end
 
-Context() do ctx
+@dispose ctx=Context() begin
     # set-up
     mod = LLVM.Module("my_module"; ctx)
 
@@ -21,7 +21,7 @@ Context() do ctx
     sum = LLVM.Function(mod, "sum", fun_type)
 
     # generate IR
-    Builder(ctx) do builder
+    @dispose builder=Builder(ctx) begin
         entry = BasicBlock(sum, "entry"; ctx)
         position!(builder, entry)
 
@@ -33,7 +33,7 @@ Context() do ctx
     end
 
     # analysis and execution
-    Interpreter(mod) do engine
+    @dispose engine=Interpreter(mod) begin
         args = [GenericValue(LLVM.Int32Type(ctx), x),
                 GenericValue(LLVM.Int32Type(ctx), y)]
 

examples/sum_integrated.jl

@@ -12,13 +12,13 @@ else
     y = Int32(2)
 end
 
-Context() do ctx
+@dispose ctx=Context() begin
     param_types = [LLVM.Int32Type(ctx), LLVM.Int32Type(ctx)]
     ret_type = LLVM.Int32Type(ctx)
     sum, _ = create_function(ret_type, param_types)
 
     # generate IR
-    Builder(ctx) do builder
+    @dispose builder=Builder(ctx) begin
         entry = BasicBlock(sum, "entry"; ctx)
         position!(builder, entry)
 

examples/sum_orc.jl

@@ -22,7 +22,7 @@ function codegen!(mod::LLVM.Module, name, tm)
     sum = LLVM.Function(mod, name, ft)
 
     # generate IR
-    Builder(ctx) do builder
+    @dispose builder=Builder(ctx) begin
         entry = BasicBlock(sum, "entry"; ctx)
         position!(builder, entry)
 
@@ -32,7 +32,7 @@ function codegen!(mod::LLVM.Module, name, tm)
 
     verify(mod)
 
-    ModulePassManager() do pm
+    @dispose pm=ModulePassManager() begin
         add_library_info!(pm, triple(mod))
         add_transform_info!(pm, tm)
         run!(pm, mod)
@@ -61,7 +61,7 @@ if LLVM.has_orc_v2()
     finalizer(LLVM.dispose, lljit)
     JIT = lljit
 else
-    Context() do ctx
+    @dispose ctx=Context() begin
         # Setup jit
         tm = JITTargetMachine()
 

src/base.jl

@@ -65,3 +65,45 @@ end
 @inline function refcheck(::Type, ref::Ptr)
     ref==C_NULL && throw(UndefRefError())
 end
+
+
+## helper macro for disposing resources without do-block syntax
+
+export @dispose
+
+"""
+    LLVM.@dispose foo=Foo() bar=Bar() begin
+        ...
+    end
+
+Helper macro for disposing resources (by calling the `LLVM.dispose` function for every
+resource in reverse order) after executing a block of code. This is often equivalent to
+calling the recourse constructor with do-block syntax, but without using (potentially
+costly) closures.
+"""
+macro dispose(ex...)
+    resources = ex[1:end-1]
+    code = ex[end]
+
+    Meta.isexpr(code, :block) ||
+        error("Expected a code block as final argument to LLVM.@dispose")
+
+    cleanup = quote
+    end
+    for res in reverse(resources)
+        Meta.isexpr(res, :(=)) ||
+            error("Resource arguments to LLVM.@dispose should be assignments")
+        push!(cleanup.args, :(LLVM.dispose($(res.args[1]))))
+    end
+
+    ex = quote
+        let $(resources...)
+            try
+                $code
+            finally
+                $(cleanup.args...)
+            end
+        end
+    end
+    esc(ex)
+end

src/core/type.jl

@@ -281,7 +281,7 @@ end
 
 # FIXME: remove on LLVM 12
 function LLVMGetTypeByName2(ctx::Context, name)
-    Module("dummy"; ctx) do mod
+    @dispose mod=Module("dummy"; ctx) begin
         API.LLVMGetTypeByName(mod, name)
     end
 end

src/core/value/constant.jl

@@ -537,8 +537,8 @@ linkage!(val::GlobalValue, linkage::API.LLVMLinkage) =
 function section(val::GlobalValue)
   #=
   The following started to fail on LLVM 4.0:
-    Context() do ctx
-      LLVM.Module("SomeModule"; ctx) do mod
+    @dispose ctx=Context() begin
+      @dispose mod=LLVM.Module("SomeModule"; ctx) begin
         st = LLVM.StructType("SomeType"; ctx)
         ft = LLVM.FunctionType(st, [st])
         fn = LLVM.Function(mod, "SomeFunction", ft)