cmd/vendor/golang.org/x/arch/arm64/arm64asm: test zero register mismatch

[prattmic]

I got this when testing near HEAD:

--- FAIL: TestObjdumpARM64Testdata (2.20s)
	ext_test.go:195: decode(744bbf38) = "ldrsb x20, [x27,wzr,uxtw]", 4, want "ldrsb x20, [x27,w31,uxtw]", 4
		
	ext_test.go:195: decode(29493fbc) = "str s9, [x9,wzr,uxtw]", 4, want "str s9, [x9,w31,uxtw]", 4
		
	ext_test.go:195: decode(225bff38) = "ldrsb w2, [x25,wzr,uxtw #0]", 4, want "ldrsb w2, [x25,w31,uxtw #0]", 4
		
	ext_test.go:195: decode(cad8bf78) = "ldrsh x10, [x6,wzr,sxtw #1]", 4, want "ldrsh x10, [x6,w31,sxtw #1]", 4
		
	ext_test.go:195: decode(a278ff3c) = "ldr q2, [x5,xzr,lsl #4]", 4, want "ldr q2, [x5,x31,lsl #4]", 4
		
	ext_test.go:195: decode(a278ff3c) = "ldr q2, [x5,xzr,lsl #4]", 4, want "ldr q2, [x5,x31,lsl #4]", 4
		
	ext_test.go:201: 9203 test cases, 686 expected mismatches, 6 failures; 5781 cases/second
	ext_test.go:202: decoder coverage: 95.5%;
	ext_test.go:201: 9203 test cases, 0 expected mismatches, 0 failures; 17619 cases/second
	ext_test.go:202: decoder coverage: 95.5%;
FAIL
FAIL	cmd/vendor/golang.org/x/arch/arm64/arm64asm	10.074s

From ARMv8 ARM: "In instruction encodings, the value 0b11111 (31) is used to indicate the ZR (zero register)."

So this appears to be a disagreement with objdump about whether to call registers w/xzr or w/x31.

I'm not sure exactly which version of objdump was running on this machine. I can dig around to find it if it would help.

[andybons]

@prattmic what revision were you testing at? Were you running all.bash?

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)