cmd/asm: add MRC and MCR to end-to-end test for arm

The old, per-architecture operand printers didn't lock down the
format of the constant in the MRC and MCR instructions (a value
that could be presented more helpfully - maybe how the
input looks? - but that is an issue for another day). But there is
a portable standard printer now so we can enable tests for these
instructions.

Change-Id: I437a3b112ce63f4d6e1fe3450fc21d8c3372602f
Reviewed-on: https://go-review.googlesource.com/7420Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/asm/internal/asm/endtoend_test.go

@@ -56,7 +56,7 @@ func testEndToEnd(t *testing.T, goarch string) {
 		r := strings.Split(result, "\n")
 		e := strings.Split(string(expect), "\n")
 		if len(r) != len(e) {
-			t.Errorf("%s: expected %d lines, got %d", len(e), len(r))
+			t.Errorf("%s: expected %d lines, got %d", goarch, len(e), len(r))
 		}
 		n := len(e)
 		if n > len(r) {

src/cmd/asm/internal/asm/testdata/arm.out

@@ -45,9 +45,11 @@
 201 00045 (testdata/arm.s:201)	ADDD.S	F1, F2, F3
 202 00046 (testdata/arm.s:202)	ADDD.S	$(0.5), F2, F3
 208 00047 (testdata/arm.s:208)	CMPD.S	F1, F2
-242 00048 (testdata/arm.s:242)	MULL	R1, R2, (R3, R4)
-254 00049 (testdata/arm.s:254)	MULAWT	R1, R2, R3, R4
-262 00050 (testdata/arm.s:262)	PLD	(R1)
-263 00051 (testdata/arm.s:263)	PLD	4(R1)
-272 00052 (testdata/arm.s:272)	RET
-281 00053 (testdata/arm.s:281)	END
+232 00048 (testdata/arm.s:232)	MRC	$8301712627
+233 00049 (testdata/arm.s:233)	MRC	$8300664051
+242 00050 (testdata/arm.s:242)	MULL	R1, R2, (R3, R4)
+254 00051 (testdata/arm.s:254)	MULAWT	R1, R2, R3, R4
+262 00052 (testdata/arm.s:262)	PLD	(R1)
+263 00053 (testdata/arm.s:263)	PLD	4(R1)
+272 00054 (testdata/arm.s:272)	RET
+281 00055 (testdata/arm.s:281)	END

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

@@ -229,8 +229,8 @@ TEXT	foo(SB), 0, $0
 //			(1<<4));			/* must be set */
 //		outcode(AMRC, Always, &nullgen, 0, &g);
 //	}
-// TODO: Disabled until printout for this instruction is the same for 32 and 64 bits.
-//	MRC.S	4, 6, R1, C2, C3, 7
+	MRC.S	4, 6, R1, C2, C3, 7
+	MCR.S	4, 6, R1, C2, C3, 7
 
 //
 // MULL r1,r2,(hi,lo)