Revert "cmd/compile,runtime: allocate defer records on the stack"

This reverts commit fff4f599fe1c21e411a99de5c9b3777d06ce0ce6.

Reason for revert: Seems to still have issues around GC.

Fixes #32452

Change-Id: Ibe7af629f9ad6a3d5312acd7b066123f484da7f0
Reviewed-on: https://go-review.googlesource.com/c/go/+/180761
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

1 files changed, 0 insertions, 44 deletions

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index ce26eb540d..f39a4bc0a2 100644
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -228,46 +228,6 @@ func deferproc(siz int32, fn *funcval) { // arguments of fn follow fn
 	// been set and must not be clobbered.
 }
 
-// deferprocStack queues a new deferred function with a defer record on the stack.
-// The defer record must have its siz and fn fields initialized.
-// All other fields can contain junk.
-// The defer record must be immediately followed in memory by
-// the arguments of the defer.
-// Nosplit because the arguments on the stack won't be scanned
-// until the defer record is spliced into the gp._defer list.
-//go:nosplit
-func deferprocStack(d *_defer) {
-	gp := getg()
-	if gp.m.curg != gp {
-		// go code on the system stack can't defer
-		throw("defer on system stack")
-	}
-	// siz and fn are already set.
-	// The other fields are junk on entry to deferprocStack and
-	// are initialized here.
-	d.started = false
-	d.heap = false
-	d.sp = getcallersp()
-	d.pc = getcallerpc()
-	// The lines below implement:
-	//   d.panic = nil
-	//   d.link = gp._defer
-	//   gp._defer = d
-	// But without write barriers. The first two are writes to
-	// the stack so they don't need a write barrier, and furthermore
-	// are to uninitialized memory, so they must not use a write barrier.
-	// The third write does not require a write barrier because we
-	// explicitly mark all the defer structures, so we don't need to
-	// keep track of pointers to them with a write barrier.
-	*(*uintptr)(unsafe.Pointer(&d._panic)) = 0
-	*(*uintptr)(unsafe.Pointer(&d.link)) = uintptr(unsafe.Pointer(gp._defer))
-	*(*uintptr)(unsafe.Pointer(&gp._defer)) = uintptr(unsafe.Pointer(d))
-
-	return0()
-	// No code can go here - the C return register has
-	// been set and must not be clobbered.
-}
-
 // Small malloc size classes >= 16 are the multiples of 16: 16, 32, 48, 64, 80, 96, 112, 128, 144, ...
 // Each P holds a pool for defers with small arg sizes.
 // Assign defer allocations to pools by rounding to 16, to match malloc size classes.
@@ -389,7 +349,6 @@ func newdefer(siz int32) *_defer {
 		}
 	}
 	d.siz = siz
-	d.heap = true
 	d.link = gp._defer
 	gp._defer = d
 	return d
@@ -409,9 +368,6 @@ func freedefer(d *_defer) {
 	if d.fn != nil {
 		freedeferfn()
 	}
-	if !d.heap {
-		return
-	}
 	sc := deferclass(uintptr(d.siz))
 	if sc >= uintptr(len(p{}.deferpool)) {
 		return