The allocation of register parameter spill space is weird.
Register Allocation and Spilling via Graph Coloring G. J. Chaitin IBM Research, ppt download
Bartosz Adamczewski on Twitter: "What is Stack Spill: (The more general name is Register Spill, where we say that the value spilled to memory) #dotnet #programming #compilers https://t.co/p80jpZsMb4" / Twitter