[AVR] At least one of llc and llvm-mc's output is wrong

[gergoerdi]

I can take this LLVM IR file, and compile it into an object file in two possible ways:

1. Straight via llc -filetype=obj
2. Going via an assembly file with llc -filetype=asm, and then assembling that with llvm-mc

I would expect the two paths to yield the same object file; however, I get two object files that are different in very wild ways. In particular, there are lots of branches that are assembled differently:

colordiff -u worduino-avr.ll.o.dump worduino-avr.ll.s.o.dump
--- worduino-avr.ll.o.dump	2023-01-12 19:57:31.962629460 +0800
+++ worduino-avr.ll.s.o.dump	2023-01-12 19:57:32.022629930 +0800
@@ -83,7 +83,7 @@
       96:	45 91       	lpm	r20, Z+
       98:	4d 93       	st	X+, r20
       9a:	31 50       	subi	r19, 0x01	; 1
-      9c:	e1 f7       	brne	.-8      	; 0x96 <_ZN15worduino_engine4draw11draw_sprite17hc7657142962e61a4E+0x96>
+      9c:	01 f4       	brne	.+0      	; 0x9e <_ZN15worduino_engine4draw11draw_sprite17hc7657142962e61a4E+0x9e>
       9e:	38 2f       	mov	r19, r24
       a0:	32 0f       	add	r19, r18
       a2:	a3 2f       	mov	r26, r19

Surely at least one of these two outputs must be wrong; I suspect brne .+0 (i.e. the output of llvm-mc) can't be right, but that doesn't necessarily mean the other is correct either.

To reproduce, check out https://github.com/gergoerdi/llvm-issue-59962/tree/c942e79b663dcab1dee9d9a8c2d0079d321cd19d and run make.

[benshi001]

This is a bug duplicates to #47093

[gergoerdi]

As of 5fcdf76 (i.e. with 6dc85bd included) I am still seeing the same problem in llvm-mc's output.