Wasm backend C-Call correctness issue

Reported in a test-primops run:

C-Call correctness:     FAIL (4.81s)
    *** Failed! Falsified (after 4 tests):
    CCallDesc {callRet = SomeNumber @W64 0xe2b35a3ebf953893, callRetSignedness = Signed, callArgs = [(Unsigned,SomeNumber @W32 0x198523b),(Unsigned,SomeNumber @W64 0xd9de2003c9cf4ce5),(Signed,SomeNumber @W64 0xa4724e1472e1a8fc),(Unsigned,SomeNumber @W64 0xfdbab4c631bb6a14)]}
    [26759739,15699020551702924517,-6597124654410651396,18283124400594840084,3214227603] /= [26759739,15699020551702924517,-6597124654410651396,18283124400594840084,16335499498951620755]
    Use --quickcheck-replay=934040 to reproduce.
    Use -p '/C-Call correctness/' to rerun this test only.