Update EIP-7480: implicit zero-padding on out-of-bounds access

Merged by EIP-Bot.

EIPS/eip-7480.md

@@ -39,8 +39,8 @@ If the code is valid EOF1, the following execution rules apply:
 ### `DATALOAD`
 
 1. Pops one value, `offset`, from the stack.
-2. If `offset + 32` is greater than the data section size of the active container, execution results in exceptional halt.
-3. Reads `[offset:offset+32]` segment from the data section and pushes it as 32-byte value to the stack.
+2. Reads `[offset:offset+32]` segment from the data section and pushes it as 32-byte value to the stack.
+3. If `offset + 32` is greater than the data section size, bytes after the end of data section are set to 0.
 4. Deducts 4 gas.
 
 ### `DATALOADN`
@@ -63,8 +63,8 @@ If the code is valid EOF1, the following execution rules apply:
 1. Pops three values from the stack: `mem_offset`, `offset`, `size`.
 2. Performs memory expansion to `mem_offset + size` and deducts memory expansion cost.
 3. Deducts `3 * ((size + 31) // 32)` gas for copying.
-3. If `offset + size` is greater than data section size of the active container, execution results in exceptional halt.
 4. Reads `[offset:offset+size]` segment from the data section and writes it to memory starting at offset `mem_offset`.
+5. If `offset + size` is greater than data section size, 0 bytes will be copied for bytes after the end of the data section.
 
 
 ### Code Validation
@@ -77,7 +77,11 @@ We extend code section validation rules (as defined in [EIP-3670](./eip-3670.md)
 
 ## Rationale
 
-TBA
+### Zero-padding on out of bounds access
+
+Existing instructions for reading other kinds of data implicitly pad with zeroes on out of bounds access, with the only exception of return data copying.
+
+It is benefitial to avoid exceptional failures, because compilers can employ optimizations like removing a code that copies data, but never accesses this copy afterwards, but such optimization is possible only if instruction never has other side effects like exceptional abort.
 
 ## Backwards Compatibility