Heap and Stack checks
Source files: rts/HeapStackCheck.cmm
When allocating a heap object, we bump Hp and compare to HpLim. If the test fails we branch to ???. Usually this code tests an interrupt flag (to see if execution should be brought tidily to a halt); grabs the next block of allocation space; makes Hp point to it and HpLim to its end; and returns. If there are no more allocation-space blocks, garbage collection is triggered.