Lowering of cglobal

Special case lowering of the first (sym,lib) argument to cglobal.

Also lower the identifiers `cglobal` and `ccall` to `K"core"`
psuedo-refs very early, ensuring that cglobal and ccall can never be
turned into normal bindings (and thus never be assigned to local or
global variables).

Also fixes handling of ccall/foreigncall (sym,lib) argument.

Author: c42f

src/ast.jl

@@ -517,6 +517,13 @@ end
 #-------------------------------------------------------------------------------
 # Predicates and accessors working on expression trees
 
+# For historical reasons, `cglobal` and `ccall` are their own special
+# quasi-identifier-like syntax but with special handling inside lowering which
+# means they can't be used as normal identifiers.
+function is_ccall_or_cglobal(name::AbstractString)
+    return name == "ccall" || name == "cglobal"
+end
+
 function is_quoted(ex)
     kind(ex) in KSet"Symbol quote top core globalref break inert
                      meta inbounds inline noinline loopinfo"
@@ -580,12 +587,16 @@ function is_valid_modref(ex)
            (kind(ex[1]) == K"Identifier" || is_valid_modref(ex[1]))
 end
 
+function is_core_ref(ex, name)
+    kind(ex) == K"core" && ex.name_val == name
+end
+
 function is_core_nothing(ex)
-    kind(ex) == K"core" && ex.name_val == "nothing"
+    is_core_ref(ex, "nothing")
 end
 
 function is_core_Any(ex)
-    kind(ex) == K"core" && ex.name_val == "Any"
+    is_core_ref(ex, "Any")
 end
 
 function is_simple_atom(ctx, ex)

src/desugaring.jl

@@ -1607,7 +1607,7 @@ function expand_kw_call(ctx, srcref, farg, args, kws)
 end
 
 function expand_ccall(ctx, ex)
-    @assert kind(ex) == K"call" && is_same_identifier_like(ex[1], "ccall")
+    @assert kind(ex) == K"call" && is_core_ref(ex[1], "ccall")
     if numchildren(ex) < 4
         throw(LoweringError(ex, "too few arguments to ccall"))
     end
@@ -1806,7 +1806,7 @@ end
 
 function expand_call(ctx, ex)
     farg = ex[1]
-    if is_same_identifier_like(farg, "ccall")
+    if is_core_ref(farg, "ccall")
         return expand_ccall(ctx, ex)
     end
     args = copy(ex[2:end])
@@ -2741,25 +2741,25 @@ function keyword_function_defs(ctx, srcref, callex_srcref, name_str,
 end
 
 # Check valid identifier/function names
-function is_valid_func_name(ex)
+function is_invalid_func_name(ex)
     k = kind(ex)
     if k == K"Identifier"
         name = ex.name_val
     elseif k == K"." && numchildren(ex) == 2 && kind(ex[2]) == K"Symbol"
         # `function A.f(x,y) ...`
         name = ex[2].name_val
     else
-        return false
+        return true
     end
-    return name != "ccall" && name != "cglobal"
+    return is_ccall_or_cglobal(name)
 end
 
 function expand_function_def(ctx, ex, docs, rewrite_call=identity, rewrite_body=identity)
     @chk numchildren(ex) in (1,2)
     name = ex[1]
     if numchildren(ex) == 1 && is_identifier_like(name)
         # Function declaration with no methods
-        if !is_valid_func_name(name)
+        if is_invalid_func_name(name)
             throw(LoweringError(name, "Invalid function name"))
         end
         return @ast ctx ex [K"block"
@@ -2837,7 +2837,7 @@ function expand_function_def(ctx, ex, docs, rewrite_call=identity, rewrite_body=
             name_str = name.name_val
             name = ssavar(ctx, name, name.name_val)
             bare_func_name = name
-        elseif !is_valid_func_name(name)
+        elseif is_invalid_func_name(name)
             throw(LoweringError(name, "Invalid function name"))
         elseif is_identifier_like(name)
             # Add methods to a global `Function` object, or local closure

src/eval.jl

@@ -203,7 +203,13 @@ function to_lowered_expr(mod, ex, ssa_offset=0)
     if is_literal(k)
         ex.value
     elseif k == K"core"
-        GlobalRef(Core, Symbol(ex.name_val))
+        name = ex.name_val
+        if name == "cglobal"
+            # cglobal isn't a true name within core - instead it's a builtin
+            :cglobal
+        else
+            GlobalRef(Core, Symbol(name))
+        end
     elseif k == K"top"
         GlobalRef(Base, Symbol(ex.name_val))
     elseif k == K"globalref"

src/linear_ir.jl

@@ -174,6 +174,19 @@ function compile_args(ctx, args)
     return args_out
 end
 
+# Compile the (sym,lib) argument to ccall/cglobal
+function compile_C_library_symbol(ctx, ex)
+    if kind(ex) == K"call" && kind(ex[1]) == K"core" && ex[1].name_val == "tuple"
+        # Tuples like core.tuple(:funcname, mylib_name) are allowed and are
+        # kept inline, but may only reference globals.
+        check_no_local_bindings(ctx, ex,
+            "function name and library expression cannot reference local variables")
+        ex
+    else
+        only(compile_args(ctx, (ex,)))
+    end
+end
+
 function emit(ctx::LinearIRContext, ex)
     push!(ctx.code, ex)
     return ex
@@ -588,18 +601,7 @@ function compile(ctx::LinearIRContext, ex, needs_value, in_tail_pos)
             k == K"new_opaque_closure" || k == K"cfunction"
         if k == K"foreigncall"
             args = SyntaxList(ctx)
-            # todo: is is_leaf correct here? flisp uses `atom?`
-            func = ex[1]
-            if kind(func) == K"call" && kind(func[1]) == K"core" && func[1].name_val == "tuple"
-                # Tuples like core.tuple(:funcname, mylib_name) are allowed,
-                # but may only reference globals.
-                check_no_local_bindings(ctx, func, "ccall function name and library expression cannot reference local variables")
-                append!(args, compile_args(ctx, ex[1:1]))
-            elseif is_leaf(func)
-                append!(args, compile_args(ctx, ex[1:1]))
-            else
-                push!(args, func)
-            end
+            push!(args, compile_C_library_symbol(ctx, ex[1]))
             # 2nd to 5th arguments of foreigncall are special. They must be
             # left in place but cannot reference locals.
             check_no_local_bindings(ctx, ex[2], "ccall return type cannot reference local variables")
@@ -621,8 +623,12 @@ function compile(ctx::LinearIRContext, ex, needs_value, in_tail_pos)
                 check_no_local_bindings(ctx, arg,
                     "cfunction argument cannot reference local variables")
             end
+        elseif k == K"call" && is_core_ref(ex[1], "cglobal")
+            args = SyntaxList(ctx)
+            push!(args, ex[1])
+            push!(args, compile_C_library_symbol(ctx, ex[2]))
+            append!(args, compile_args(ctx, ex[3:end]))
         else
-            # TODO: cglobal
             args = compile_args(ctx, children(ex))
         end
         callex = makenode(ctx, ex, k, args)

src/macro_expansion.jl

@@ -202,8 +202,16 @@ need to be dealt with before other lowering.
 """
 function expand_forms_1(ctx::MacroExpansionContext, ex::SyntaxTree)
     k = kind(ex)
-    if k == K"Identifier" && all(==('_'), ex.name_val)
-        @ast ctx ex ex=>K"Placeholder"
+    if k == K"Identifier"
+        name_str = ex.name_val
+        if all(==('_'), name_str)
+            @ast ctx ex ex=>K"Placeholder"
+        elseif is_ccall_or_cglobal(name_str)
+            @ast ctx ex name_str::K"core"
+        else
+            layerid = get(ex, :scope_layer, ctx.current_layer.id)
+            makeleaf(ctx, ex, ex, kind=K"Identifier", scope_layer=layerid)
+        end
     elseif k == K"Identifier" || k == K"MacroName" || k == K"StringMacroName"
         layerid = get(ex, :scope_layer, ctx.current_layer.id)
         makeleaf(ctx, ex, ex, kind=K"Identifier", scope_layer=layerid)

test/demo.jl

@@ -793,6 +793,10 @@ begin
 end
 """
 
+src = """
+cglobal(:jl_uv_stdin, Ptr{Cvoid})
+"""
+
 ex = parsestmt(SyntaxTree, src, filename="foo.jl")
 ex = ensure_attributes(ex, var_id=Int)
 #ex = softscope_test(ex)

test/function_calls_ir.jl

@@ -369,11 +369,9 @@ ccall((:strlen, libc), Csize_t, (Cstring,), "asdfg")
 #---------------------
 1   TestMod.Cstring
 2   (call top.cconvert %₁ "asdfg")
-3   TestMod.libc
-4   (call core.tuple :strlen %₃)
-5   (call top.unsafe_convert %₁ %₂)
-6   (foreigncall %₄ TestMod.Csize_t (call core.svec TestMod.Cstring) 0 :ccall %₅ %₂)
-7   (return %₆)
+3   (call top.unsafe_convert %₁ %₂)
+4   (foreigncall (call core.tuple :strlen TestMod.libc) TestMod.Csize_t (call core.svec TestMod.Cstring) 0 :ccall %₃ %₂)
+5   (return %₄)
 
 ########################################
 # ccall with a calling convention
@@ -458,7 +456,7 @@ end
 LoweringError:
 let libc = "libc"
     ccall((:strlen, libc), Csize_t, (Cstring,), "asdfg")
-#         └─────────────┘ ── ccall function name and library expression cannot reference local variables
+#         └─────────────┘ ── function name and library expression cannot reference local variables
 end
 
 ########################################
@@ -517,3 +515,65 @@ LoweringError:
 ccall(:foo, Csize_t, (Cstring..., Cstring...), "asdfg", "blah")
 #                     └────────┘ ── only the trailing ccall argument type should have `...`
 
+########################################
+# cglobal special support for (sym, lib) tuple
+cglobal((:sym, lib), Int)
+#---------------------
+1   TestMod.Int
+2   (call core.cglobal (call core.tuple :sym TestMod.lib) %₁)
+3   (return %₂)
+
+########################################
+# cglobal - non-tuple expressions in first arg are lowered as normal
+cglobal(f(), Int)
+#---------------------
+1   TestMod.f
+2   (call %₁)
+3   TestMod.Int
+4   (call core.cglobal %₂ %₃)
+5   (return %₄)
+
+########################################
+# Error: assigning to `cglobal`
+cglobal = 10
+#---------------------
+LoweringError:
+cglobal = 10
+└─────┘ ── invalid assignment location
+
+########################################
+# Error: assigning to `ccall`
+ccall = 10
+#---------------------
+LoweringError:
+ccall = 10
+└───┘ ── invalid assignment location
+
+########################################
+# Error: assigning to `var"ccall"`
+var"ccall" = 10
+#---------------------
+LoweringError:
+var"ccall" = 10
+#   └───┘ ── invalid assignment location
+
+########################################
+# Error: Invalid function name ccall
+function ccall()
+end
+#---------------------
+LoweringError:
+function ccall()
+#        └───┘ ── Invalid function name
+end
+
+########################################
+# Error: Invalid function name ccall
+function A.ccall()
+end
+#---------------------
+LoweringError:
+function A.ccall()
+#        └─────┘ ── Invalid function name
+end
+

test/functions_ir.jl

@@ -332,26 +332,6 @@ end
     1   (return core.nothing)
 9   (return core.nothing)
 
-########################################
-# Error: Invalid function name ccall
-function ccall()
-end
-#---------------------
-LoweringError:
-function ccall()
-#        └───┘ ── Invalid function name
-end
-
-########################################
-# Error: Invalid function name ccall
-function A.ccall()
-end
-#---------------------
-LoweringError:
-function A.ccall()
-#        └─────┘ ── Invalid function name
-end
-
 ########################################
 # Error: Invalid dotop function name
 function (.+)(x,y)