runtime: don't use linkname to refer to internal/cpu

The runtime package already imports the internal/cpu package, so there
is no reason for it to use go:linkname comments to refer to
internal/cpu functions and variables. Since internal/cpu is internal,
we can just export those names. Removing the obscurity of go:linkname
outweighs the minor additional complexity added to the internal/cpu API.

Change-Id: Id89951b7f3fc67cd9bce67ac6d01d44a647a10ad
Reviewed-on: https://go-review.googlesource.com/128755
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>

src/internal/cpu/cpu.go

@@ -6,9 +6,10 @@
 // used by the Go standard library.
 package cpu
 
-// debugOptions is set to true by the runtime if go was compiled with GOEXPERIMENT=debugcpu
-// and GOOS is Linux or Darwin. This variable is linknamed in runtime/proc.go.
-var debugOptions bool
+// DebugOptions is set to true by the runtime if go was compiled with GOEXPERIMENT=debugcpu
+// and GOOS is Linux or Darwin.
+// This should not be changed after it is initialized.
+var DebugOptions bool
 
 // CacheLinePad is used to pad structs to avoid false sharing.
 type CacheLinePad struct{ _ [CacheLineSize]byte }
@@ -121,11 +122,11 @@ type s390x struct {
 	_               CacheLinePad
 }
 
-// initialize examines the processor and sets the relevant variables above.
+// Initialize examines the processor and sets the relevant variables above.
 // This is called by the runtime package early in program initialization,
 // before normal init functions are run. env is set by runtime on Linux and Darwin
 // if go was compiled with GOEXPERIMENT=debugcpu.
-func initialize(env string) {
+func Initialize(env string) {
 	doinit()
 	processOptions(env)
 }

src/internal/cpu/cpu_arm64.go

@@ -7,10 +7,10 @@ package cpu
 const CacheLineSize = 64
 
 // arm64 doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
-// These are linknamed in runtime/os_linux_arm64.go and are initialized by
-// archauxv().
-var hwcap uint
-var hwcap2 uint
+// These are initialized by archauxv in runtime/os_linux_arm64.go.
+// These should not be changed after they are initialized.
+var HWCap uint
+var HWCap2 uint
 
 // HWCAP/HWCAP2 bits. These are exposed by Linux.
 const (
@@ -71,30 +71,30 @@ func doinit() {
 	}
 
 	// HWCAP feature bits
-	ARM64.HasFP = isSet(hwcap, hwcap_FP)
-	ARM64.HasASIMD = isSet(hwcap, hwcap_ASIMD)
-	ARM64.HasEVTSTRM = isSet(hwcap, hwcap_EVTSTRM)
-	ARM64.HasAES = isSet(hwcap, hwcap_AES)
-	ARM64.HasPMULL = isSet(hwcap, hwcap_PMULL)
-	ARM64.HasSHA1 = isSet(hwcap, hwcap_SHA1)
-	ARM64.HasSHA2 = isSet(hwcap, hwcap_SHA2)
-	ARM64.HasCRC32 = isSet(hwcap, hwcap_CRC32)
-	ARM64.HasATOMICS = isSet(hwcap, hwcap_ATOMICS)
-	ARM64.HasFPHP = isSet(hwcap, hwcap_FPHP)
-	ARM64.HasASIMDHP = isSet(hwcap, hwcap_ASIMDHP)
-	ARM64.HasCPUID = isSet(hwcap, hwcap_CPUID)
-	ARM64.HasASIMDRDM = isSet(hwcap, hwcap_ASIMDRDM)
-	ARM64.HasJSCVT = isSet(hwcap, hwcap_JSCVT)
-	ARM64.HasFCMA = isSet(hwcap, hwcap_FCMA)
-	ARM64.HasLRCPC = isSet(hwcap, hwcap_LRCPC)
-	ARM64.HasDCPOP = isSet(hwcap, hwcap_DCPOP)
-	ARM64.HasSHA3 = isSet(hwcap, hwcap_SHA3)
-	ARM64.HasSM3 = isSet(hwcap, hwcap_SM3)
-	ARM64.HasSM4 = isSet(hwcap, hwcap_SM4)
-	ARM64.HasASIMDDP = isSet(hwcap, hwcap_ASIMDDP)
-	ARM64.HasSHA512 = isSet(hwcap, hwcap_SHA512)
-	ARM64.HasSVE = isSet(hwcap, hwcap_SVE)
-	ARM64.HasASIMDFHM = isSet(hwcap, hwcap_ASIMDFHM)
+	ARM64.HasFP = isSet(HWCap, hwcap_FP)
+	ARM64.HasASIMD = isSet(HWCap, hwcap_ASIMD)
+	ARM64.HasEVTSTRM = isSet(HWCap, hwcap_EVTSTRM)
+	ARM64.HasAES = isSet(HWCap, hwcap_AES)
+	ARM64.HasPMULL = isSet(HWCap, hwcap_PMULL)
+	ARM64.HasSHA1 = isSet(HWCap, hwcap_SHA1)
+	ARM64.HasSHA2 = isSet(HWCap, hwcap_SHA2)
+	ARM64.HasCRC32 = isSet(HWCap, hwcap_CRC32)
+	ARM64.HasATOMICS = isSet(HWCap, hwcap_ATOMICS)
+	ARM64.HasFPHP = isSet(HWCap, hwcap_FPHP)
+	ARM64.HasASIMDHP = isSet(HWCap, hwcap_ASIMDHP)
+	ARM64.HasCPUID = isSet(HWCap, hwcap_CPUID)
+	ARM64.HasASIMDRDM = isSet(HWCap, hwcap_ASIMDRDM)
+	ARM64.HasJSCVT = isSet(HWCap, hwcap_JSCVT)
+	ARM64.HasFCMA = isSet(HWCap, hwcap_FCMA)
+	ARM64.HasLRCPC = isSet(HWCap, hwcap_LRCPC)
+	ARM64.HasDCPOP = isSet(HWCap, hwcap_DCPOP)
+	ARM64.HasSHA3 = isSet(HWCap, hwcap_SHA3)
+	ARM64.HasSM3 = isSet(HWCap, hwcap_SM3)
+	ARM64.HasSM4 = isSet(HWCap, hwcap_SM4)
+	ARM64.HasASIMDDP = isSet(HWCap, hwcap_ASIMDDP)
+	ARM64.HasSHA512 = isSet(HWCap, hwcap_SHA512)
+	ARM64.HasSVE = isSet(HWCap, hwcap_SVE)
+	ARM64.HasASIMDFHM = isSet(HWCap, hwcap_ASIMDFHM)
 }
 
 func isSet(hwc uint, value uint) bool {

src/internal/cpu/cpu_ppc64x.go

@@ -9,10 +9,10 @@ package cpu
 const CacheLineSize = 128
 
 // ppc64x doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
-// These are linknamed in runtime/os_linux_ppc64x.go and are initialized by
-// archauxv().
-var hwcap uint
-var hwcap2 uint
+// These are initialized by archauxv in runtime/os_linux_ppc64x.go.
+// These should not be changed after they are initialized.
+var HWCap uint
+var HWCap2 uint
 
 // HWCAP/HWCAP2 bits. These are exposed by the kernel.
 const (
@@ -48,19 +48,19 @@ func doinit() {
 	}
 
 	// HWCAP feature bits
-	PPC64.HasVMX = isSet(hwcap, _PPC_FEATURE_HAS_ALTIVEC)
-	PPC64.HasDFP = isSet(hwcap, _PPC_FEATURE_HAS_DFP)
-	PPC64.HasVSX = isSet(hwcap, _PPC_FEATURE_HAS_VSX)
+	PPC64.HasVMX = isSet(HWCap, _PPC_FEATURE_HAS_ALTIVEC)
+	PPC64.HasDFP = isSet(HWCap, _PPC_FEATURE_HAS_DFP)
+	PPC64.HasVSX = isSet(HWCap, _PPC_FEATURE_HAS_VSX)
 
 	// HWCAP2 feature bits
-	PPC64.IsPOWER8 = isSet(hwcap2, _PPC_FEATURE2_ARCH_2_07)
-	PPC64.HasHTM = isSet(hwcap2, _PPC_FEATURE2_HAS_HTM)
-	PPC64.HasISEL = isSet(hwcap2, _PPC_FEATURE2_HAS_ISEL)
-	PPC64.HasVCRYPTO = isSet(hwcap2, _PPC_FEATURE2_HAS_VEC_CRYPTO)
-	PPC64.HasHTMNOSC = isSet(hwcap2, _PPC_FEATURE2_HTM_NOSC)
-	PPC64.IsPOWER9 = isSet(hwcap2, _PPC_FEATURE2_ARCH_3_00)
-	PPC64.HasDARN = isSet(hwcap2, _PPC_FEATURE2_DARN)
-	PPC64.HasSCV = isSet(hwcap2, _PPC_FEATURE2_SCV)
+	PPC64.IsPOWER8 = isSet(HWCap2, _PPC_FEATURE2_ARCH_2_07)
+	PPC64.HasHTM = isSet(HWCap2, _PPC_FEATURE2_HAS_HTM)
+	PPC64.HasISEL = isSet(HWCap2, _PPC_FEATURE2_HAS_ISEL)
+	PPC64.HasVCRYPTO = isSet(HWCap2, _PPC_FEATURE2_HAS_VEC_CRYPTO)
+	PPC64.HasHTMNOSC = isSet(HWCap2, _PPC_FEATURE2_HTM_NOSC)
+	PPC64.IsPOWER9 = isSet(HWCap2, _PPC_FEATURE2_ARCH_3_00)
+	PPC64.HasDARN = isSet(HWCap2, _PPC_FEATURE2_DARN)
+	PPC64.HasSCV = isSet(HWCap2, _PPC_FEATURE2_SCV)
 }
 
 func isSet(hwc uint, value uint) bool {

src/internal/cpu/export_test.go

@@ -5,6 +5,5 @@
 package cpu
 
 var (
-	Options      = options
-	DebugOptions = debugOptions
+	Options = options
 )

src/runtime/os_linux_arm64.go

@@ -6,20 +6,10 @@
 
 package runtime
 
-// For go:linkname
-import _ "unsafe"
+import "internal/cpu"
 
 var randomNumber uint32
 
-// arm64 doesn't have a 'cpuid' instruction equivalent and relies on
-// HWCAP/HWCAP2 bits for hardware capabilities.
-
-//go:linkname cpu_hwcap internal/cpu.hwcap
-var cpu_hwcap uint
-
-//go:linkname cpu_hwcap2 internal/cpu.hwcap2
-var cpu_hwcap2 uint
-
 func archauxv(tag, val uintptr) {
 	switch tag {
 	case _AT_RANDOM:
@@ -28,10 +18,13 @@ func archauxv(tag, val uintptr) {
 		// it as a byte array.
 		randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
 			uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
+
 	case _AT_HWCAP:
-		cpu_hwcap = uint(val)
+		// arm64 doesn't have a 'cpuid' instruction equivalent and relies on
+		// HWCAP/HWCAP2 bits for hardware capabilities.
+		cpu.HWCap = uint(val)
 	case _AT_HWCAP2:
-		cpu_hwcap2 = uint(val)
+		cpu.HWCap2 = uint(val)
 	}
 }
 

src/runtime/os_linux_ppc64x.go

@@ -7,23 +7,16 @@
 
 package runtime
 
-// For go:linkname
-import _ "unsafe"
-
-// ppc64x doesn't have a 'cpuid' instruction equivalent and relies on
-// HWCAP/HWCAP2 bits for hardware capabilities.
-
-//go:linkname cpu_hwcap internal/cpu.hwcap
-var cpu_hwcap uint
-
-//go:linkname cpu_hwcap2 internal/cpu.hwcap2
-var cpu_hwcap2 uint
+import "internal/cpu"
 
 func archauxv(tag, val uintptr) {
 	switch tag {
 	case _AT_HWCAP:
-		cpu_hwcap = uint(val)
+		// ppc64x doesn't have a 'cpuid' instruction
+		// equivalent and relies on HWCAP/HWCAP2 bits for
+		// hardware capabilities.
+		cpu.HWCap = uint(val)
 	case _AT_HWCAP2:
-		cpu_hwcap2 = uint(val)
+		cpu.HWCap2 = uint(val)
 	}
 }

src/runtime/proc.go

@@ -477,20 +477,14 @@ const (
 	_GoidCacheBatch = 16
 )
 
-//go:linkname internal_cpu_initialize internal/cpu.initialize
-func internal_cpu_initialize(env string)
-
-//go:linkname internal_cpu_debugOptions internal/cpu.debugOptions
-var internal_cpu_debugOptions bool
-
 // cpuinit extracts the environment variable GODEBUGCPU from the environment on
-// Linux and Darwin if the GOEXPERIMENT debugcpu was set and calls internal/cpu.initialize.
+// Linux and Darwin if the GOEXPERIMENT debugcpu was set and calls internal/cpu.Initialize.
 func cpuinit() {
 	const prefix = "GODEBUGCPU="
 	var env string
 
 	if haveexperiment("debugcpu") && (GOOS == "linux" || GOOS == "darwin") {
-		internal_cpu_debugOptions = true
+		cpu.DebugOptions = true
 
 		// Similar to goenv_unix but extracts the environment value for
 		// GODEBUGCPU directly.
@@ -511,7 +505,7 @@ func cpuinit() {
 		}
 	}
 
-	internal_cpu_initialize(env)
+	cpu.Initialize(env)
 
 	support_erms = cpu.X86.HasERMS
 	support_popcnt = cpu.X86.HasPOPCNT