(Motivation: "Literal" is a syntactic property, not a semantic one.)
Also: delete a "TODO: opt" that the lifting pass already does for us.
R=gri
CC=golang-dev
https://golang.org/cl/11351043
This CL adds three new functions to determine the SSA Value
for a given syntactic var, func or const object:
Program.{Const,Func,Var}Value.
Since constants and functions are immutable, the first
two only need a types.Object; but each distinct
reference to a var may return a distinct Value, so the third
requires an ast.Ident parameter too.
Debug information for local vars is encoded in the
instruction stream in the form of DebugRef instructions,
which are a no-op but relate their operand to a particular
ident in the AST. The beauty of this approach is that it
naturally stays consistent during optimisation passes
(e.g. lifting) without additional bookkeeping.
DebugRef instructions are only generated if the DebugMode
builder flag is set; I plan to make the policy more fine-
grained (per function).
DebugRef instructions are inserted for:
- expr(Ident) for rvalue idents
- address.store() for idents that update an lvalue
- address.address() for idents that take address of lvalue
(this new method replaces all uses of lval.(address).addr)
- expr() for all constant expressions
- local ValueSpecs with implicit zero initialization (no RHS)
(this case doesn't call store() or address())
To ensure we don't forget to emit debug info for uses of Idents,
we must use the lvalue mechanism consistently. (Previously,
many simple cases had effectively inlined these functions.)
Similarly setCallFunc no longer inlines expr(Ident).
Also:
- Program.Value() has been inlined & specialized.
- Program.Package() has moved nearer the new lookup functions.
- refactoring: funcSyntax has lost paramFields, resultFields;
gained funcType, which provides access to both.
- add package-level constants to Package.values map.
- opt: don't call localValueSpec for constants.
(The resulting code is always optimised away.)
There are a number of comments asking whether Literals
should have positions. Will address in a follow-up.
Added tests of all interesting cases.
R=gri
CC=golang-dev
https://golang.org/cl/11259044
