runtime: remove unused function casp

Change-Id: I7c9c83ba236e1050e04377a7591fef7174df698b
Reviewed-on: https://go-review.googlesource.com/130415
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/atomic_pointer.go

@@ -13,8 +13,6 @@ import (
 // because while ptr does not escape, new does.
 // If new is marked as not escaping, the compiler will make incorrect
 // escape analysis decisions about the pointer value being stored.
-// Instead, these are wrappers around the actual atomics (casp1 and so on)
-// that use noescape to convey which arguments do not escape.
 
 // atomicwb performs a write barrier before an atomic pointer write.
 // The caller should guard the call with "if writeBarrier.enabled".
@@ -37,17 +35,6 @@ func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
 	atomic.StorepNoWB(noescape(ptr), new)
 }
 
-//go:nosplit
-func casp(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
-	// The write barrier is only necessary if the CAS succeeds,
-	// but since it needs to happen before the write becomes
-	// public, we have to do it conservatively all the time.
-	if writeBarrier.enabled {
-		atomicwb(ptr, new)
-	}
-	return atomic.Casp1((*unsafe.Pointer)(noescape(unsafe.Pointer(ptr))), noescape(old), new)
-}
-
 // Like above, but implement in terms of sync/atomic's uintptr operations.
 // We cannot just call the runtime routines, because the race detector expects
 // to be able to intercept the sync/atomic forms but not the runtime forms.

src/runtime/proc.go

@@ -1599,7 +1599,7 @@ func allocm(_p_ *p, fn func()) *m {
 // the following strategy: there is a stack of available m's
 // that can be stolen. Using compare-and-swap
 // to pop from the stack has ABA races, so we simulate
-// a lock by doing an exchange (via casp) to steal the stack
+// a lock by doing an exchange (via Casuintptr) to steal the stack
 // head and replace the top pointer with MLOCKED (1).
 // This serves as a simple spin lock that we can use even
 // without an m. The thread that locks the stack in this way

src/runtime/runtime1.go

@@ -145,7 +145,7 @@ func check() {
 		h     uint64
 		i, i1 float32
 		j, j1 float64
-		k, k1 unsafe.Pointer
+		k     unsafe.Pointer
 		l     *uint16
 		m     [4]byte
 	)
@@ -234,21 +234,6 @@ func check() {
 		throw("cas6")
 	}
 
-	k = unsafe.Pointer(uintptr(0xfedcb123))
-	if sys.PtrSize == 8 {
-		k = unsafe.Pointer(uintptr(k) << 10)
-	}
-	if casp(&k, nil, nil) {
-		throw("casp1")
-	}
-	k1 = add(k, 1)
-	if !casp(&k, k, k1) {
-		throw("casp2")
-	}
-	if k != k1 {
-		throw("casp3")
-	}
-
 	m = [4]byte{1, 1, 1, 1}
 	atomic.Or8(&m[1], 0xf0)
 	if m[0] != 1 || m[1] != 0xf1 || m[2] != 1 || m[3] != 1 {