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perf: truncate to i64 before jumping to dynamic jump table #317

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perf: truncate to i64 before jumping to dynamic jump table #317

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7b70741
perf: truncate to i64 before jumping to dynamic jump table
DaniPopes Apr 20, 2026
275c49d
fix: use saturating i256-to-i64 convert at jump site
DaniPopes Apr 20, 2026
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18 changes: 9 additions & 9 deletions crates/revmc/src/compiler/translate/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -366,16 +366,8 @@ impl<'a, B: Backend> FunctionCx<'a, B> {
let targets = jumpdests
.map(|(inst, data)| (data.pc as u64, fx.inst_entries[inst]))
.collect::<Vec<_>>();
let index = fx.bcx.phi(fx.word_type, &fx.incoming_dynamic_jumps);

// Saturating convert i256 to i64: if the value doesn't fit, select u64::MAX
// which won't match any valid jump target.
let i64_type = fx.bcx.type_int(64);
let reduced = fx.bcx.ireduce(i64_type, index);
let extended = fx.bcx.zext(fx.word_type, reduced);
let fits = fx.bcx.icmp(IntCC::Equal, index, extended);
let sentinel = fx.bcx.iconst(i64_type, u64::MAX as i64);
let index = fx.bcx.select(fits, reduced, sentinel);
let index = fx.bcx.phi(i64_type, &fx.incoming_dynamic_jumps);
fx.add_invalid_jump();
fx.bcx.switch(index, return_block, &targets, true);
} else {
Expand Down Expand Up @@ -1002,6 +994,14 @@ impl<'a, B: Backend> FunctionCx<'a, B> {
// Dynamic jump.
debug_assert!(self.bytecode.has_dynamic_jumps());
let target = self.pop();
// Saturating convert i256 to i64: if the value doesn't fit,
// select u64::MAX which won't match any valid jump target.
let i64_type = self.bcx.type_int(64);
let reduced = self.bcx.ireduce(i64_type, target);
let extended = self.bcx.zext(self.word_type, reduced);
let fits = self.bcx.icmp(IntCC::Equal, target, extended);
let sentinel = self.bcx.iconst(i64_type, u64::MAX as i64);
let target = self.bcx.select(fits, reduced, sentinel);
self.incoming_dynamic_jumps
.push((target, self.bcx.current_block().unwrap()));
self.dynamic_jump_table
Expand Down
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