[llvm] [ARM] Fix failure to register-allocate CMP_SWAP_64 pseudo-inst (PR #106721)

[Simon Tatham via llvm-commits]

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@@ -78,15 +78,14 @@ define { i32, i1 } @test_cmpxchg_32(ptr %addr, i32 %desired, i32 %new) nounwind
 
 define { i64, i1 } @test_cmpxchg_64(ptr %addr, i64 %desired, i64 %new) nounwind {
 ; CHECK-LABEL: test_cmpxchg_64:
-; CHECK:     mov [[ADDR:r[0-9]+]], r0
 ; CHECK:     dmb ish
 ; CHECK-NOT: uxt
 ; CHECK: [[RETRY:.LBB[0-9]+_[0-9]+]]:
-; CHECK:     ldrexd [[OLDLO:r[0-9]+]], [[OLDHI:r[0-9]+]], [[[ADDR]]]
+; CHECK:     ldrexd [[OLDLO:r[0-9]+]], [[OLDHI:r[0-9]+]], [r0]
 ; CHECK:     cmp [[OLDLO]], r6
 ; CHECK:     cmpeq [[OLDHI]], r7
 ; CHECK:     bne [[DONE:.LBB[0-9]+_[0-9]+]]
-; CHECK:     strexd [[STATUS:[lr0-9]+]], r8, r9, [r1]
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statham-arm wrote:

This made me scratch my head when I was trying to work out how the new version matched up to it! I think the `[r1]` here should have been another `[[[ADDR]]]`, because in the real output, ADDR is r1 anyway. I suppose in the new version you do just expect the address to stay in r0, because there was no reason to move it.

https://github.com/llvm/llvm-project/pull/106721