poly1305: use x/sys/cpu for s390x feature detection

Use the recently added CPU feature detection API rather than custom
assembly. This will need to be updated to use 'internal/cpu' when
the package is revendored into std.

Change-Id: Ia99c51c7409fe4fabcd88fdf5ff19772c1ca2257
Reviewed-on: https://go-review.googlesource.com/c/164382
Reviewed-by: Brad Fitzpatrick <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: mundaym

Diff for: poly1305/sum_s390x.go

@@ -6,16 +6,9 @@
 
 package poly1305
 
-// hasVectorFacility reports whether the machine supports
-// the vector facility (vx).
-func hasVectorFacility() bool
-
-// hasVMSLFacility reports whether the machine supports
-// Vector Multiply Sum Logical (VMSL).
-func hasVMSLFacility() bool
-
-var hasVX = hasVectorFacility()
-var hasVMSL = hasVMSLFacility()
+import (
+	"golang.org/x/sys/cpu"
+)
 
 // poly1305vx is an assembly implementation of Poly1305 that uses vector
 // instructions. It must only be called if the vector facility (vx) is
@@ -33,12 +26,12 @@ func poly1305vmsl(out *[16]byte, m *byte, mlen uint64, key *[32]byte)
 // 16-byte result into out. Authenticating two different messages with the same
 // key allows an attacker to forge messages at will.
 func Sum(out *[16]byte, m []byte, key *[32]byte) {
-	if hasVX {
+	if cpu.S390X.HasVX {
 		var mPtr *byte
 		if len(m) > 0 {
 			mPtr = &m[0]
 		}
-		if hasVMSL && len(m) > 256 {
+		if cpu.S390X.HasVXE && len(m) > 256 {
 			poly1305vmsl(out, mPtr, uint64(len(m)), key)
 		} else {
 			poly1305vx(out, mPtr, uint64(len(m)), key)

Diff for: poly1305/sum_s390x.s

@@ -376,25 +376,3 @@ b1:
 
 	MOVD $0, R3
 	BR   multiply
-
-TEXT ·hasVectorFacility(SB), NOSPLIT, $24-1
-	MOVD  $x-24(SP), R1
-	XC    $24, 0(R1), 0(R1) // clear the storage
-	MOVD  $2, R0            // R0 is the number of double words stored -1
-	WORD  $0xB2B01000       // STFLE 0(R1)
-	XOR   R0, R0            // reset the value of R0
-	MOVBZ z-8(SP), R1
-	AND   $0x40, R1
-	BEQ   novector
-
-vectorinstalled:
-	// check if the vector instruction has been enabled
-	VLEIB  $0, $0xF, V16
-	VLGVB  $0, V16, R1
-	CMPBNE R1, $0xF, novector
-	MOVB   $1, ret+0(FP)      // have vx
-	RET
-
-novector:
-	MOVB $0, ret+0(FP) // no vx
-	RET

Diff for: poly1305/sum_vmsl_s390x.s

@@ -907,25 +907,3 @@ square:
 	MULTIPLY(H0_0, H1_0, H2_0, H0_1, H1_1, H2_1, R_0, R_1, R_2, R5_1, R5_2, M0, M1, M2, M3, M4, M5, T_0, T_1, T_2, T_3, T_4, T_5, T_6, T_7, T_8, T_9)
 	REDUCE2(H0_0, H1_0, H2_0, M0, M1, M2, M3, M4, T_9, T_10, H0_1, M5)
 	BR next
-
-TEXT ·hasVMSLFacility(SB), NOSPLIT, $24-1
-	MOVD  $x-24(SP), R1
-	XC    $24, 0(R1), 0(R1) // clear the storage
-	MOVD  $2, R0            // R0 is the number of double words stored -1
-	WORD  $0xB2B01000       // STFLE 0(R1)
-	XOR   R0, R0            // reset the value of R0
-	MOVBZ z-8(SP), R1
-	AND   $0x01, R1
-	BEQ   novmsl
-
-vectorinstalled:
-	// check if the vector instruction has been enabled
-	VLEIB  $0, $0xF, V16
-	VLGVB  $0, V16, R1
-	CMPBNE R1, $0xF, novmsl
-	MOVB   $1, ret+0(FP)    // have vx
-	RET
-
-novmsl:
-	MOVB $0, ret+0(FP) // no vx
-	RET