cmd/asm,cmd/internal/obj/x86: add RDPID instruction to x86 assembler

Add support for the Read Processor ID (RDPID) instruction to the x86
assembler. This returns the current logical processor's ID in the
specified register, as a faster alternative to RDTSCP.

Fixes #56525

Change-Id: I43482e42431dfc385ce2e7f6d44b9746b0cc4548
Reviewed-on: https://go-review.googlesource.com/c/go/+/482955
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

src/cmd/asm/internal/asm/testdata/386enc.s

@@ -33,5 +33,8 @@ TEXT asmtest(SB),DUPOK|NOSPLIT,$0
 	PUSHL FS // 0fa0
 	POPL FS  // 0fa1
 	POPL SS  // 17
+
+	RDPID AX                                // f30fc7f8
+
 	// End of tests.
 	RET

src/cmd/asm/internal/asm/testdata/amd64enc_extra.s

@@ -1055,5 +1055,9 @@ TEXT asmtest(SB),DUPOK|NOSPLIT,$0
 	TPAUSE BX // 660faef3
 	UMONITOR BX // f30faef3
 	UMWAIT BX // f20faef3
+
+	RDPID DX                                // f30fc7fa
+	RDPID R11                               // f3410fc7fb
+
 	// End of tests.
 	RET

src/cmd/asm/internal/asm/testdata/amd64error.s

@@ -144,4 +144,7 @@ TEXT errors(SB),$0
 	VMOVDQA32.Z Z0, Z1               // ERROR "mask register must be specified for .Z instructions"
 	VMOVDQA32.Z Z0, K0, Z1           // ERROR "invalid instruction"
 	VMOVDQA32.Z Z0, K1, Z1           // ok
+
+	RDPID (BX)			 // ERROR "invalid instruction"
+
 	RET

src/cmd/internal/obj/x86/aenum.go

@@ -747,6 +747,7 @@ const (
 	ARDGSBASEL
 	ARDGSBASEQ
 	ARDMSR
+	ARDPID
 	ARDPKRU
 	ARDPMC
 	ARDRANDL

src/cmd/internal/obj/x86/anames.go

@@ -745,6 +745,7 @@ var Anames = []string{
 	"RDGSBASEL",
 	"RDGSBASEQ",
 	"RDMSR",
+	"RDPID",
 	"RDPKRU",
 	"RDPMC",
 	"RDRANDL",

src/cmd/internal/obj/x86/asm6.go

@@ -775,7 +775,7 @@ var ymshufb = []ytab{
 }
 
 // It should never have more than 1 entry,
-// because some optab entries you opcode secuences that
+// because some optab entries have opcode sequences that
 // are longer than 2 bytes (zoffset=2 here),
 // ROUNDPD and ROUNDPS and recently added BLENDPD,
 // to name a few.
@@ -1774,6 +1774,7 @@ var optab =
 	{ALSSW, ym_rl, Pe, opBytes{0x0f, 0xb2}},
 	{ALSSL, ym_rl, Px, opBytes{0x0f, 0xb2}},
 	{ALSSQ, ym_rl, Pw, opBytes{0x0f, 0xb2}},
+	{ARDPID, yrdrand, Pf3, opBytes{0xc7, 07}},
 
 	{ABLENDPD, yxshuf, Pq, opBytes{0x3a, 0x0d, 0}},
 	{ABLENDPS, yxshuf, Pq, opBytes{0x3a, 0x0c, 0}},

src/cmd/internal/obj/x86/obj6.go

@@ -1476,6 +1476,7 @@ var unaryDst = map[obj.As]bool{
 	ARDFSBASEQ:  true,
 	ARDGSBASEL:  true,
 	ARDGSBASEQ:  true,
+	ARDPID:      true,
 	ARDRANDL:    true,
 	ARDRANDQ:    true,
 	ARDRANDW:    true,