Instruction.previous_instruction()

Returns a list of immediate previous instructions in the control flow graph.

previous_instruction() → APISet[Instruction]

The difference between the previous_instruction() function and previous_instructions() is that this function will return a list of immediate previous instructions of the current instruction in the CFG (control-flow-graph).

The function operates non-recursively, meaning it works intra-procedurally.

For example, in the function:

function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

for the instruction:

uint256 c = a - b;

the function will return the instruction:

require(b <= a, errorMessage);

Query Example

from glider import *
def query():
  instructions = Functions().with_name("sub").exec(1,1).instructions().exec(1,2)

  return instructions + list(instructions[0].previous_instruction())

Output Example

The function returns APISet, instead of APIList, in case the result of the function is used as the return value of the query it must be casted to list()