memcpy test inexplicably failing

I have started seeing failures in the memcpy test:

diff -uw "codeGen/should_gen_asm/memcpy.run/memcpy.asm.normalised" "codeGen/should_gen_asm/memcpy.run/memcpy.s.normalised"
--- codeGen/should_gen_asm/memcpy.run/memcpy.asm.normalised	2018-12-11 23:13:18.763730758 -0500
+++ codeGen/should_gen_asm/memcpy.run/memcpy.s.normalised	2018-12-11 23:13:18.763730758 -0500
@@ -1,9 +1,9 @@
 callMemcpy:
+subq
 movq
 movq
 movl
-subq
-movl
+xorl
 call memcpy
 addq
 jmp

The failures aren't themselves concerning; the new assembler is perfectly valid:

.section .text
.align 8
.globl callMemcpy
.type callMemcpy, @function
callMemcpy:
.Lc6:
        movl $1024,%eax
        subq $8,%rsp
        movq %rax,%rdx
        movq %rbx,%rdi
        movq %r14,%rsi
        xorl %eax,%eax
        call memcpy
        addq $8,%rsp
        jmp *(%rbp)
        .size callMemcpy, .-callMemcpy
.section .note.GNU-stack,"",@progbits
.ident "GHC 8.7.20181211"

However, I have no explanation for why this suddenly started happening.

Trac metadata

Trac field	Value
Version	8.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed milestone to %8.8.1

changed weight to 7

added Tbug Trac import labels

mentioned in commit 251db979

I have accepted the new output but would really like to understand why this changed. I believe the change arose somewhere between 856dd66f and 65fb69b7.

changed milestone to %8.10.1

added Phigh label

Given that both the new and old code are correct, I'm going to close this.

closed