Effects

[freesig]

Idea

Functions indicate which effects they need access to in a bitmap. This allows the VM to run them in the correct context and combine the multiple VMs into one. If an op is hit that the effect isn't enabled for then the predicate will panic.

Effects

Some potential effects

• State
• Looping
• Jump Forward
• Jump Anywhere
• Mutable memory
• Read access to previous functions memory
• Mutable access to previous functions memory
• Panic
• Expensive functions like crypto

Implementation

Use a byte at the start of any function and have bit flags for each effect. Max 8 effects

[mitchmindtree]

Just noting that effects analysis has since been implemented in #196, but we don't yet make use of this in essential-check.