sha3: use x/sys/cpu for s390x feature detection

Use the recently added CPU feature detection API rather than custom
assembly.

While we are here also make vet happy by renaming params in the asm
file to chain to match the go function declaration.

Change-Id: Ide0171793c9fa5ef6671b394e97a27f2c6e44a9f
Reviewed-on: https://go-review.googlesource.com/c/164381
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

sha3/sha3_s390x.go

diff --git a/sha3/sha3_s390x.go b/sha3/sha3_s390x.go
index f1fb79c..b6cbc5c 100644
--- a/sha3/sha3_s390x.go
+++ b/sha3/sha3_s390x.go
@@ -12,6 +12,8 @@
 
 import (
 	"hash"
+
+	"golang.org/x/sys/cpu"
 )
 
 // codes represent 7-bit KIMD/KLMD function codes as defined in
@@ -29,13 +31,6 @@
 	nopad          = 0x100
 )
 
-// hasMSA6 reports whether the machine supports the SHA-3 and SHAKE function
-// codes, as defined in message-security-assist extension 6.
-func hasMSA6() bool
-
-// hasAsm caches the result of hasMSA6 (which might be expensive to call).
-var hasAsm = hasMSA6()
-
 // kimd is a wrapper for the 'compute intermediate message digest' instruction.
 // src must be a multiple of the rate for the given function code.
 //go:noescape
@@ -237,7 +232,7 @@
 // new224Asm returns an assembly implementation of SHA3-224 if available,
 // otherwise it returns nil.
 func new224Asm() hash.Hash {
-	if hasAsm {
+	if cpu.S390X.HasSHA3 {
 		return newAsmState(sha3_224)
 	}
 	return nil
@@ -246,7 +241,7 @@
 // new256Asm returns an assembly implementation of SHA3-256 if available,
 // otherwise it returns nil.
 func new256Asm() hash.Hash {
-	if hasAsm {
+	if cpu.S390X.HasSHA3 {
 		return newAsmState(sha3_256)
 	}
 	return nil
@@ -255,7 +250,7 @@
 // new384Asm returns an assembly implementation of SHA3-384 if available,
 // otherwise it returns nil.
 func new384Asm() hash.Hash {
-	if hasAsm {
+	if cpu.S390X.HasSHA3 {
 		return newAsmState(sha3_384)
 	}
 	return nil
@@ -264,7 +259,7 @@
 // new512Asm returns an assembly implementation of SHA3-512 if available,
 // otherwise it returns nil.
 func new512Asm() hash.Hash {
-	if hasAsm {
+	if cpu.S390X.HasSHA3 {
 		return newAsmState(sha3_512)
 	}
 	return nil
@@ -273,7 +268,7 @@
 // newShake128Asm returns an assembly implementation of SHAKE-128 if available,
 // otherwise it returns nil.
 func newShake128Asm() ShakeHash {
-	if hasAsm {
+	if cpu.S390X.HasSHA3 {
 		return newAsmState(shake_128)
 	}
 	return nil
@@ -282,7 +277,7 @@
 // newShake256Asm returns an assembly implementation of SHAKE-256 if available,
 // otherwise it returns nil.
 func newShake256Asm() ShakeHash {
-	if hasAsm {
+	if cpu.S390X.HasSHA3 {
 		return newAsmState(shake_256)
 	}
 	return nil

sha3/sha3_s390x.s

diff --git a/sha3/sha3_s390x.s b/sha3/sha3_s390x.s
index 20978fc..b2ef69f 100644
--- a/sha3/sha3_s390x.s
+++ b/sha3/sha3_s390x.s
@@ -6,26 +6,10 @@
 
 #include "textflag.h"
 
-TEXT ·hasMSA6(SB), NOSPLIT, $16-1
-	MOVD $0, R0          // KIMD-Query function code
-	MOVD $tmp-16(SP), R1 // parameter block
-	XC   $16, (R1), (R1) // clear the parameter block
-	WORD $0xB93E0002     // KIMD --, --
-	WORD $0x91FC1004     // TM 4(R1), 0xFC (test bits [32-37])
-	BVS  yes
-
-no:
-	MOVB $0, ret+0(FP)
-	RET
-
-yes:
-	MOVB $1, ret+0(FP)
-	RET
-
-// func kimd(function code, params *[200]byte, src []byte)
+// func kimd(function code, chain *[200]byte, src []byte)
 TEXT ·kimd(SB), NOFRAME|NOSPLIT, $0-40
 	MOVD function+0(FP), R0
-	MOVD params+8(FP), R1
+	MOVD chain+8(FP), R1
 	LMG  src+16(FP), R2, R3 // R2=base, R3=len
 
 continue:
@@ -34,11 +18,11 @@
 	MOVD $0, R0      // reset R0 for pre-go1.8 compilers
 	RET
 
-// func klmd(function code, params *[200]byte, dst, src []byte)
+// func klmd(function code, chain *[200]byte, dst, src []byte)
 TEXT ·klmd(SB), NOFRAME|NOSPLIT, $0-64
 	// TODO: SHAKE support
 	MOVD function+0(FP), R0
-	MOVD params+8(FP), R1
+	MOVD chain+8(FP), R1
 	LMG  dst+16(FP), R2, R3 // R2=base, R3=len
 	LMG  src+40(FP), R4, R5 // R4=base, R5=len