internal/cpu, runtime: add CPU feature detection support for AIX

AIX doesn't have HWCAP/HWCAP2 variables like Linux. Therefore, it relies on
getsystemcfg syscall which can provide some information about the CPU.

Change-Id: Ic0dc927e80890d4bf8f0bdfb43fad1e2b890d7a0
Reviewed-on: https://go-review.googlesource.com/c/144959
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>

src/internal/cpu/cpu_ppc64x.go

@@ -11,18 +11,19 @@ const CacheLinePadSize = 128
 // ppc64x doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
 // These are initialized by archauxv in runtime/os_linux_ppc64x.go.
 // These should not be changed after they are initialized.
+// On aix/ppc64, these values are initialized early in the runtime in runtime/os_aix.go.
 var HWCap uint
 var HWCap2 uint
 
 // HWCAP/HWCAP2 bits. These are exposed by the kernel.
 const (
 	// ISA Level
-	_PPC_FEATURE2_ARCH_2_07 = 0x80000000
-	_PPC_FEATURE2_ARCH_3_00 = 0x00800000
+	PPC_FEATURE2_ARCH_2_07 = 0x80000000
+	PPC_FEATURE2_ARCH_3_00 = 0x00800000
 
 	// CPU features
-	_PPC_FEATURE2_DARN = 0x00200000
-	_PPC_FEATURE2_SCV  = 0x00100000
+	PPC_FEATURE2_DARN = 0x00200000
+	PPC_FEATURE2_SCV  = 0x00100000
 )
 
 func doinit() {
@@ -36,10 +37,10 @@ func doinit() {
 	}
 
 	// HWCAP2 feature bits
-	PPC64.IsPOWER8 = isSet(HWCap2, _PPC_FEATURE2_ARCH_2_07)
-	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.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/runtime/os2_aix.go

@@ -33,6 +33,7 @@ var (
 //go:cgo_import_dynamic libc_close close "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_exit exit "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_getpid getpid "libc.a/shr_64.o"
+//go:cgo_import_dynamic libc_getsystemcfg getsystemcfg "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_kill kill "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_madvise madvise "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_malloc malloc "libc.a/shr_64.o"
@@ -69,6 +70,7 @@ var (
 //go:linkname libc_close libc_close
 //go:linkname libc_exit libc_exit
 //go:linkname libc_getpid libc_getpid
+//go:linkname libc_getsystemcfg libc_getsystemcfg
 //go:linkname libc_kill libc_kill
 //go:linkname libc_madvise libc_madvise
 //go:linkname libc_malloc libc_malloc
@@ -107,6 +109,7 @@ var (
 	libc_close,
 	libc_exit,
 	libc_getpid,
+	libc_getsystemcfg,
 	libc_kill,
 	libc_madvise,
 	libc_malloc,
@@ -319,6 +322,12 @@ func sigaltstack(new, old *stackt) {
 	}
 }
 
+//go:nosplit
+func getsystemcfg(label uint) uintptr {
+	r, _ := syscall1(&libc_getsystemcfg, uintptr(label))
+	return r
+}
+
 //go:nosplit
 func usleep(us uint32) {
 	r, err := syscall1(&libc_usleep, uintptr(us))

src/runtime/os_aix.go

@@ -7,6 +7,7 @@
 package runtime
 
 import (
+	"internal/cpu"
 	"unsafe"
 )
 
@@ -93,6 +94,7 @@ func semawakeup(mp *m) {
 func osinit() {
 	ncpu = int32(sysconf(__SC_NPROCESSORS_ONLN))
 	physPageSize = sysconf(__SC_PAGE_SIZE)
+	setupSystemConf()
 }
 
 // Ms related functions
@@ -260,3 +262,22 @@ func walltime() (sec int64, nsec int32) {
 	}
 	return ts.tv_sec, int32(ts.tv_nsec)
 }
+
+const (
+	// getsystemcfg constants
+	_SC_IMPL     = 2
+	_IMPL_POWER8 = 0x10000
+	_IMPL_POWER9 = 0x20000
+)
+
+// setupSystemConf retrieves information about the CPU and updates
+// cpu.HWCap variables.
+func setupSystemConf() {
+	impl := getsystemcfg(_SC_IMPL)
+	if impl&_IMPL_POWER8 != 0 {
+		cpu.HWCap2 |= cpu.PPC_FEATURE2_ARCH_2_07
+	}
+	if impl&_IMPL_POWER9 != 0 {
+		cpu.HWCap2 |= cpu.PPC_FEATURE2_ARCH_3_00
+	}
+}