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!fixup Address review comments.

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This commit is contained in:
Jim Posen 2019-07-11 16:45:46 +02:00
parent b3f8f62105
commit b5472bcd8f
1 changed files with 17 additions and 23 deletions
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40
src/gas.rs
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@ -128,8 +128,6 @@ impl Counter {
// If there may have been a branch to a lower index, then also finalize the active metered
// block for the previous control block. Otherwise, finalize it and begin a new one.
//
// TODO: handle diverging function calls.
let may_br_out = closing_control_block.lowest_forward_br < closing_control_index;
if may_br_out {
self.finalize_metered_block(cursor)?;
@ -153,9 +151,9 @@ impl Counter {
)
};
// If the block was opened with a `begin`, then its start position will be set to that of
// If the block was opened with a `block`, then its start position will be set to that of
// the active metered block in the control block one higher on the stack. This is because
// any instructions between a `begin` and the first branch are part of the same basic block
// any instructions between a `block` and the first branch are part of the same basic block
// as the preceding instruction. In this case, instead of finalizing the block, merge its
// cost into the other active metered block to avoid injecting unnecessary instructions.
let last_index = self.stack.len() - 1;
@ -183,7 +181,7 @@ impl Counter {
self.finalize_metered_block(cursor)?;
// Update the lowest_forward_br of the current control block.
for index in indices.iter().cloned() {
for &index in indices {
let target_is_loop = {
let target_block = self.stack.get(index).ok_or_else(|| ())?;
target_block.is_loop
@ -199,20 +197,20 @@ impl Counter {
Ok(())
}
/// Returns the height of the control stack.
fn stack_height(&self) -> usize {
self.stack.len()
/// Returns the stack index of the active control block. Returns None if stack is empty.
fn active_control_block_index(&self) -> Option<usize> {
self.stack.len().checked_sub(1)
}
/// Get a reference to the currently active metered block.
fn active_block(&mut self) -> Result<&mut MeteredBlock, ()> {
fn active_metered_block(&mut self) -> Result<&mut MeteredBlock, ()> {
let top_block = self.stack.last_mut().ok_or_else(|| ())?;
Ok(&mut top_block.active_metered_block)
}
/// Increment the cost of the current block by the specified value.
fn increment(&mut self, val: u32) -> Result<(), ()> {
let top_block = self.active_block()?;
let top_block = self.active_metered_block()?;
top_block.cost = top_block.cost.checked_add(val).ok_or_else(|| ())?;
Ok(())
}
@ -278,9 +276,7 @@ pub fn inject_counter(
// be included into this block. The start position is set to that of the previous
// active metered block to signal that they should be merged in order to reduce
// unnecessary metering instructions.
let top_block_start_pos = counter.active_block()
.expect("stack is not empty; qed")
.start_pos;
let top_block_start_pos = counter.active_metered_block()?.start_pos;
counter.begin_control_block(top_block_start_pos, false);
}
If(_) => {
@ -301,19 +297,19 @@ pub fn inject_counter(
counter.increment(instruction_cost)?;
// Label is a relative index into the control stack.
let index = counter.stack_height().checked_sub(1 + label as usize)
.ok_or_else(|| ())?;
counter.branch(cursor, &[index])?;
let active_index = counter.active_control_block_index().ok_or_else(|| ())?;
let target_index = active_index.checked_sub(label as usize).ok_or_else(|| ())?;
counter.branch(cursor, &[target_index])?;
}
BrTable(ref label_vec, label_default) => {
counter.increment(instruction_cost)?;
let stack_height = counter.stack_height();
let indices = [label_default].iter().chain(label_vec.iter())
.map(|label| stack_height.checked_sub(1 + *label as usize))
let active_index = counter.active_control_block_index().ok_or_else(|| ())?;
let target_indices = [label_default].iter().chain(label_vec.iter())
.map(|label| active_index.checked_sub(*label as usize))
.collect::<Option<Vec<_>>>()
.ok_or_else(|| ())?;
counter.branch(cursor, &indices)?;
counter.branch(cursor, &target_indices)?;
}
Return => {
counter.increment(instruction_cost)?;
@ -350,8 +346,7 @@ fn insert_metering_calls(
blocks.sort_unstable_by_key(|block| block.start_pos);
let mut block_iter = blocks.into_iter().peekable();
let mut original_pos = 0;
for instr in original_instrs.into_iter() {
for (original_pos, instr) in original_instrs.into_iter().enumerate() {
// If there the next block starts at this position, inject metering instructions.
let used_block = if let Some(ref block) = block_iter.peek() {
if block.start_pos == original_pos {
@ -367,7 +362,6 @@ fn insert_metering_calls(
// Copy over the original instruction.
new_instrs.push(instr);
original_pos += 1;
}
if block_iter.next().is_some() {