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runtime: remove implicit NOFRAME heuristic support

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All amd64 OSes already make use of the NOFRAME flag wherever is
required, so we can remove the frameless nosplit functions heuristic
code path.

Updates #58378

Change-Id: I966970693ba07f8c66da0aca83c23caad7cbbfe5
Reviewed-on: https://go-review.googlesource.com/c/go/+/466458
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
qmuntal 2023-02-08 16:51:34 +01:00 committed by Quim Muntal
parent a5f3cb6f75
commit d20e688fcf
2 changed files with 2 additions and 15 deletions
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16
src/cmd/internal/obj/x86/obj6.go
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@ -614,27 +614,15 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
}
}
var usefpheuristic bool
switch ctxt.Headtype {
case objabi.Hwindows, objabi.Hdarwin, objabi.Hlinux, objabi.Hdragonfly,
objabi.Hfreebsd, objabi.Hnetbsd, objabi.Hopenbsd, objabi.Hsolaris, objabi.Hplan9:
default:
usefpheuristic = true
}
var bpsize int
if ctxt.Arch.Family == sys.AMD64 &&
!p.From.Sym.NoFrame() && // (1) below
!(autoffset == 0 && p.From.Sym.NoSplit() && usefpheuristic) && // (2) below
!(autoffset == 0 && !hasCall) { // (3) below
!(autoffset == 0 && !hasCall) { // (2) below
// Make room to save a base pointer.
// There are 2 cases we must avoid:
// 1) If noframe is set (which we do for functions which tail call).
// 2) Scary runtime internals which would be all messed up by frame pointers.
// We detect these using a heuristic: frameless nosplit functions.
// TODO: Maybe someday we label them all with NOFRAME and get rid of this heuristic.
// For performance, we also want to avoid:
// 3) Frameless leaf functions
// 2) Frameless leaf functions
bpsize = ctxt.Arch.PtrSize
autoffset += int32(bpsize)
p.To.Offset += int64(bpsize)

1
src/runtime/textflag.h
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@ -28,7 +28,6 @@
#define TLSBSS 256
// Do not insert instructions to allocate a stack frame for this function.
// Only valid on functions that declare a frame size of 0.
// TODO(mwhudson): only implemented for ppc64x at present.
#define NOFRAME 512
// Function can call reflect.Type.Method or reflect.Type.MethodByName.
#define REFLECTMETHOD 1024