runtime: remove unused xchgp/xchgp1

I noticed that they were unimplemented on arm64 but then that they were
in fact not used at all.

Change-Id: Iee579feda2a5e374fa571bcc8c89e4ef607d50f6
Reviewed-on: https://go-review.googlesource.com/13951
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/asm_386.s

@@ -551,13 +551,6 @@ TEXT runtime·xchg(SB), NOSPLIT, $0-12
 	MOVL	AX, ret+8(FP)
 	RET
 
-TEXT runtime·xchgp1(SB), NOSPLIT, $0-12
-	MOVL	ptr+0(FP), BX
-	MOVL	new+4(FP), AX
-	XCHGL	AX, 0(BX)
-	MOVL	AX, ret+8(FP)
-	RET
-
 TEXT runtime·xchguintptr(SB), NOSPLIT, $0-12
 	JMP	runtime·xchg(SB)
 

src/runtime/asm_amd64.s

@@ -563,13 +563,6 @@ TEXT runtime·xchg64(SB), NOSPLIT, $0-24
 	MOVQ	AX, ret+16(FP)
 	RET
 
-TEXT runtime·xchgp1(SB), NOSPLIT, $0-24
-	MOVQ	ptr+0(FP), BX
-	MOVQ	new+8(FP), AX
-	XCHGQ	AX, 0(BX)
-	MOVQ	AX, ret+16(FP)
-	RET
-
 TEXT runtime·xchguintptr(SB), NOSPLIT, $0-24
 	JMP	runtime·xchg64(SB)
 

src/runtime/asm_amd64p32.s

@@ -517,13 +517,6 @@ TEXT runtime·xchg64(SB), NOSPLIT, $0-24
 	MOVQ	AX, ret+16(FP)
 	RET
 
-TEXT runtime·xchgp1(SB), NOSPLIT, $0-12
-	MOVL	ptr+0(FP), BX
-	MOVL	new+4(FP), AX
-	XCHGL	AX, 0(BX)
-	MOVL	AX, ret+8(FP)
-	RET
-
 TEXT runtime·xchguintptr(SB), NOSPLIT, $0-12
 	JMP	runtime·xchg(SB)
 

src/runtime/asm_ppc64x.s

@@ -584,9 +584,6 @@ TEXT runtime·xchg64(SB), NOSPLIT, $0-24
 	MOVD	R3, ret+16(FP)
 	RET
 
-TEXT runtime·xchgp1(SB), NOSPLIT, $0-24
-	BR	runtime·xchg64(SB)
-
 TEXT runtime·xchguintptr(SB), NOSPLIT, $0-24
 	BR	runtime·xchg64(SB)
 

src/runtime/atomic_386.go

@@ -52,9 +52,6 @@ func xadd(ptr *uint32, delta int32) uint32
 //go:noescape
 func xchg(ptr *uint32, new uint32) uint32
 
-// NO go:noescape annotation; see atomic_pointer.go.
-func xchgp1(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer
-
 //go:noescape
 func xchguintptr(ptr *uintptr, new uintptr) uintptr
 

src/runtime/atomic_amd64x.go

@@ -45,9 +45,6 @@ func xchg(ptr *uint32, new uint32) uint32
 //go:noescape
 func xchg64(ptr *uint64, new uint64) uint64
 
-// NO go:noescape annotation; see atomic_pointer.go.
-func xchgp1(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer
-
 //go:noescape
 func xchguintptr(ptr *uintptr, new uintptr) uintptr
 

src/runtime/atomic_arm.go

@@ -41,16 +41,6 @@ func xchg(addr *uint32, v uint32) uint32 {
 	}
 }
 
-//go:nosplit
-func xchgp1(addr unsafe.Pointer, v unsafe.Pointer) unsafe.Pointer {
-	for {
-		old := *(*unsafe.Pointer)(addr)
-		if casp1((*unsafe.Pointer)(addr), old, v) {
-			return old
-		}
-	}
-}
-
 //go:nosplit
 func xchguintptr(addr *uintptr, v uintptr) uintptr {
 	return uintptr(xchg((*uint32)(unsafe.Pointer(addr)), uint32(v)))

src/runtime/atomic_arm64.go

@@ -22,9 +22,6 @@ func xchg(ptr *uint32, new uint32) uint32
 //go:noescape
 func xchg64(ptr *uint64, new uint64) uint64
 
-// NO go:noescape annotation; see atomic_pointer.go.
-func xchgp1(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer
-
 //go:noescape
 func xchguintptr(ptr *uintptr, new uintptr) uintptr
 

src/runtime/atomic_pointer.go

@@ -10,7 +10,7 @@ import "unsafe"
 // 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 (xchgp1 and so on)
+// Instead, these are wrappers around the actual atomics (casp1 and so on)
 // that use noescape to convey which arguments do not escape.
 //
 // Additionally, these functions must update the shadow heap for
@@ -22,13 +22,6 @@ func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
 	writebarrierptr_nostore((*uintptr)(ptr), uintptr(new))
 }
 
-//go:nosplit
-func xchgp(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer {
-	old := xchgp1(noescape(ptr), new)
-	writebarrierptr_nostore((*uintptr)(ptr), uintptr(new))
-	return old
-}
-
 //go:nosplit
 func casp(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
 	if !casp1((*unsafe.Pointer)(noescape(unsafe.Pointer(ptr))), noescape(old), new) {

src/runtime/atomic_ppc64x.go

@@ -24,9 +24,6 @@ func xchg(ptr *uint32, new uint32) uint32
 //go:noescape
 func xchg64(ptr *uint64, new uint64) uint64
 
-// NO go:noescape annotation; see atomic_pointer.go.
-func xchgp1(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer
-
 //go:noescape
 func xchguintptr(ptr *uintptr, new uintptr) uintptr