Comment after JMP at indentation level 0

[mmcloughlin]

I have the following:

// Code generated by command: go run asm.go -out sum.s -stubs stub.go. DO NOT EDIT.

#include "textflag.h"

// func Sum(xs []uint64) uint64
TEXT ·Sum(SB), NOSPLIT, $0-32
	MOVQ xs_base(FP), AX
	MOVQ xs_len+8(FP), CX

	// Initialize sum register to zero.
	XORQ DX, DX

	// Loop until zero bytes remain.
loop:
	CMPQ CX, $0x00
	JE   done

	// Load from pointer and add to running sum.
	ADDQ (AX), DX

	// Advance pointer, decrement byte count.
	ADDQ $0x08, AX
	DECQ CX
	JMP  loop

	// Store sum to return value.
done:
	MOVQ DX, ret+24(FP)
	RET

I am not sure I agree with the asmfmt result here:

$ asmfmt -d ./examples/sum/sum.s
diff ./examples/sum/sum.s asmfmt/./examples/sum/sum.s
--- /var/folders/p5/84p384bs42v7pbgfx0db9gq80000gn/T/asmfmt374566857	2019-01-11 12:30:24.000000000 -0800
+++ /var/folders/p5/84p384bs42v7pbgfx0db9gq80000gn/T/asmfmt487530132	2019-01-11 12:30:24.000000000 -0800
@@ -23,7 +23,7 @@
 	DECQ CX
 	JMP  loop

-	// Store sum to return value.
+// Store sum to return value.
 done:
 	MOVQ DX, ret+24(FP)
 	RET

Is this intended behavior?

[klauspost]

The comment is intended to document what is below. The label is considered "global" and is therefore not indented, and the comment above keeps that indentation. So yes, it is intended.

If you want it indented, it can be moved to after the label

[mmcloughlin]

Why does it move the comment before "done" but not the comment before "loop"?

[mmcloughlin]

I think this is a minimal example of what I'm asking:

$ cat labelcomments.s
#include "textflag.h"

TEXT ·LabelComments(SB), NOSPLIT, $0-32
	XORQ AX, AX
	// A
a:
	JMP b
	// B
b:
	XORQ AX, AX
$ asmfmt labelcomments.s
#include "textflag.h"

TEXT ·LabelComments(SB), NOSPLIT, $0-32
	XORQ AX, AX

	// A
a:
	JMP b

// B
b:
	XORQ AX, AX

[klauspost]

JMP and RET are considered terminators meaning they terminate the block they are in.

Comments are seen as belonging to whatever is following them. Therefore the B is considered as belonging to the b label.

[mmcloughlin]

I know what terminator instructions are. It does not seem right to me that they should affect formatting in this way.

Comments are seen as belonging to whatever is following them.

This seems reasonable. Therefore A should belong to the a label also.

Anyway, seems clear that you intended it to work this way, and we just happen to disagree.