Memory estimates for account calls

gas.md

@@ -493,7 +493,9 @@ not include the code loading cost.
 
 Also, it may seem counterintuitive to pay for the code loading cost, one may
 expect to pay a flat fee as in the EVM model. A flat fee is usually less
-efficient, so we're using a size-based fee.
+efficient, so we're using a size-based fee. There is a similar memory
+consumption associated with loading the code which, arguably, might be included
+in a flat-fee cost.
 
   ```hs
   -- CALLOP in [CALL, CALLCODE, DELEGATECALL, STATICCALL]
@@ -528,8 +530,37 @@ efficient, so we're using a size-based fee.
 
   newAccountSetupCost(CALL) = accountCreationCost + accountTransferCost
   newAccountSetupCost(CALLCODE|DELEGATECALL|STATICCALL) = 0
+
+  -- Memory increase/decrease follows a similar pattern
+
+  memoryDelta(early-failling, CALLOP) =
+      registerSize 0 - registerSize REG
+  memoryDelta(inexistent-account-late-failure) =
+      registerSize 0 - registerSize REG
+  memoryDelta(inexistent-account-success) = 0
+      registerSize 0 - registerSize REG
+
+  -- Temporary memory increase, i.e. the memory increases until the error is
+  -- detected, then it goes back to its initial value. I.e. it might be a good
+  -- idea to just update the max memory usage (if needed) and not the currently
+  -- used memory.
+  memorySpikeSize(existent-account-late-failure) = codeSize
+  -- The spike is followed by a normal memory delta.
+  memoryDelta(existent-account-late-failure) =
+      registerSize 0 - registerSize REG
+
+  memoryDeltaCaller(existent-account-success) = codeSize + constantMemorySize
+  memorySizeCallee(existent-account-success) = callDataSize
   ```
 
+  The calee starts with a memory usage of memorySizeCallee (absolute, not a
+  delta). There is a free memory allowance for each new contract call, equal to
+  the maximum EVM stack size, that will be taken into account separately.
+
+  `constantMemorySize` is the size of whatever is part of the saved state
+  except for the code and callData (calldepth, callValue, id, gas, caller,
+  static)
+
 TODO: I (virgil) think that these costs are more reasonable than some costs
       which follow the semantics in detail. However, we should be able to use
       them inside the semantics, so we should make sure that this is possible.