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cmd/compile: use fixVariadicCall in escape analysis

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This CL uses fixVariadicCall before escape analyzing function calls.
This has a number of benefits, though also some minor obstacles:

Most notably, it allows us to remove ODDDARG along with the logic
involved in setting it up, manipulating EscHoles, and later copying
its escape analysis flags to the actual slice argument. Instead, we
uniformly handle all variadic calls the same way. (E.g., issue31573.go
is updated because now f() and f(nil...) are handled identically.)

It also allows us to simplify handling of builtins and generic
function calls. Previously handling of calls was hairy enough to
require multiple dispatches on n.Op, whereas now the logic is uniform
enough that we can easily handle it with a single dispatch.

The downside is handling //go:uintptrescapes is now somewhat clumsy.
(It used to be clumsy, but it still is, too.) The proper fix here is
probably to stop using escape analysis tags for //go:uintptrescapes
and unsafe-uintptr, and have an earlier pass responsible for them.

Finally, note that while we now call fixVariadicCall in Escape, we
still have to call it in Order, because we don't (yet) run Escape on
all compiler-generated functions. In particular, the generated "init"
function for initializing package-level variables can contain calls to
variadic functions and isn't escape analyzed.

Passes toolstash-check -race.

Change-Id: I4cdb92a393ac487910aeee58a5cb8c1500eef881
Reviewed-on: https://go-review.googlesource.com/c/go/+/229759
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Matthew Dempsky 2020-04-21 19:48:02 -07:00
parent 83d25c61e4
commit a44d06d3b4
5 changed files with 119 additions and 157 deletions
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4
src/cmd/compile/internal/gc/syntax.go
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@ -686,10 +686,8 @@ const (
// OCALLFUNC, OCALLMETH, and OCALLINTER have the same structure.
// Prior to walk, they are: Left(List), where List is all regular arguments.
// If present, Right is an ODDDARG that holds the
// generated slice used in a call to a variadic function.
// After walk, List is a series of assignments to temporaries,
// and Rlist is an updated set of arguments, including any ODDDARG slice.
// and Rlist is an updated set of arguments.
// TODO(josharian/khr): Use Ninit instead of List for the assignments to temporaries. See CL 114797.
OCALLFUNC // Left(List/Rlist) (function call f(args))
OCALLMETH // Left(List/Rlist) (direct method call x.Method(args))