From 3d721812f0a4948a54b1c98528a55b618e92ee6c Mon Sep 17 00:00:00 2001 From: Jakub Doka Date: Sat, 26 Oct 2024 20:29:31 +0200 Subject: [PATCH] adding better dead code elimination --- lang/README.md | 16 +++ lang/src/codegen.rs | 2 +- lang/src/son.rs | 108 ++++++++++++++++----- lang/src/vc.rs | 9 -- lang/tests/son_tests_dead_code_in_loop.txt | 6 ++ 5 files changed, 107 insertions(+), 34 deletions(-) create mode 100644 lang/tests/son_tests_dead_code_in_loop.txt diff --git a/lang/README.md b/lang/README.md index 1e114e6..e451902 100644 --- a/lang/README.md +++ b/lang/README.md @@ -1100,3 +1100,19 @@ main := fn(): uint { return *mem } ``` + +#### dead_code_in_loop +```hb +main := fn(): uint { + n := 0 + + loop if n < 10 { + if n < 10 break + n += 1 + } else break + + loop if n == 0 return n + + return 1 +} +``` diff --git a/lang/src/codegen.rs b/lang/src/codegen.rs index 61bf40f..01581a0 100644 --- a/lang/src/codegen.rs +++ b/lang/src/codegen.rs @@ -12,7 +12,7 @@ use { TypeParser, TypedReloc, Types, }, alloc::{string::String, vec::Vec}, - core::{assert_matches::debug_assert_matches, fmt::Display, usize}, + core::{assert_matches::debug_assert_matches, fmt::Display}, }; type Offset = u32; diff --git a/lang/src/son.rs b/lang/src/son.rs index 25f6a12..cb174f1 100644 --- a/lang/src/son.rs +++ b/lang/src/son.rs @@ -316,13 +316,10 @@ impl Nodes { fn iter_peeps(&mut self, mut fuel: usize) { self.lock(NEVER); - for n in self[VOID].outputs.clone() { - if self[n].kind == Kind::Arg { - self.lock(n); - } - } - - let mut stack = self.iter().map(|(id, ..)| id).collect::>(); + let mut stack = self + .iter() + .filter_map(|(id, node)| node.kind.is_peeped().then_some(id)) + .collect::>(); stack.iter().for_each(|&s| self.lock(s)); while fuel != 0 @@ -336,20 +333,14 @@ impl Nodes { if let Some(new) = new { let prev_len = stack.len(); for &i in self[new].outputs.iter().chain(self[new].inputs.iter()) { - if self[i].lock_rc == 0 { - stack.push(i) + if self[i].kind.is_peeped() && self[i].lock_rc == 0 { + stack.push(i); } } stack.iter().skip(prev_len).for_each(|&n| self.lock(n)); } } - for n in self[VOID].outputs.clone() { - if self[n].kind == Kind::Arg { - self.unlock(n); - } - } - self.unlock(NEVER); } @@ -464,16 +455,75 @@ impl Nodes { } } K::If => { - let cond = self[target].inputs[1]; - if let K::CInt { value } = self[cond].kind { - let ty = if value == 0 { - ty::Id::LEFT_UNREACHABLE - } else { - ty::Id::RIGHT_UNREACHABLE - }; - return Some(self.new_node_nop(ty, K::If, [self[target].inputs[0], cond])); + if self[target].ty == ty::Id::VOID { + let &[ctrl, cond] = self[target].inputs.as_slice() else { unreachable!() }; + if let K::CInt { value } = self[cond].kind { + let ty = if value == 0 { + ty::Id::LEFT_UNREACHABLE + } else { + ty::Id::RIGHT_UNREACHABLE + }; + return Some(self.new_node_nop(ty, K::If, [ctrl, cond])); + } + + 'b: { + let mut cursor = ctrl; + let ty = loop { + if cursor == ENTRY { + break 'b; + } + + // TODO: do more inteligent checks on the condition + if self[cursor].kind == Kind::Then + && self[self[cursor].inputs[0]].inputs[1] == cond + { + break ty::Id::RIGHT_UNREACHABLE; + } + if self[cursor].kind == Kind::Else + && self[self[cursor].inputs[0]].inputs[1] == cond + { + break ty::Id::LEFT_UNREACHABLE; + } + + cursor = idom(self, cursor); + }; + + return Some(self.new_node_nop(ty, K::If, [ctrl, cond])); + } } } + K::Then => { + if self[self[target].inputs[0]].ty == ty::Id::LEFT_UNREACHABLE { + return Some(NEVER); + } else if self[self[target].inputs[0]].ty == ty::Id::RIGHT_UNREACHABLE { + return Some(self[self[target].inputs[0]].inputs[0]); + } + } + K::Else => { + if self[self[target].inputs[0]].ty == ty::Id::RIGHT_UNREACHABLE { + return Some(NEVER); + } else if self[self[target].inputs[0]].ty == ty::Id::LEFT_UNREACHABLE { + return Some(self[self[target].inputs[0]].inputs[0]); + } + } + K::Region => { + let (ctrl, side) = match self[target].inputs.as_slice() { + [NEVER, NEVER] => return Some(NEVER), + &[NEVER, ctrl] => (ctrl, 2), + &[ctrl, NEVER] => (ctrl, 1), + _ => return None, + }; + + self.lock(target); + for i in self[target].outputs.clone() { + if self[i].kind == Kind::Phi { + self.replace(i, self[i].inputs[side]); + } + } + self.unlock(target); + + return Some(ctrl); + } K::Phi => { let &[ctrl, lhs, rhs] = self[target].inputs.as_slice() else { unreachable!() }; @@ -532,6 +582,10 @@ impl Nodes { } } K::Loop => { + if self[target].inputs[0] == NEVER { + return Some(NEVER); + } + if self[target].inputs[1] == NEVER { self.lock(target); for o in self[target].outputs.clone() { @@ -554,6 +608,7 @@ impl Nodes { } fn replace(&mut self, target: Nid, with: Nid) { + debug_assert_ne!(target, with, "{:?}", self[target]); let mut back_press = 0; for i in 0..self[target].outputs.len() { let out = self[target].outputs[i - back_press]; @@ -570,7 +625,7 @@ impl Nodes { fn modify_input(&mut self, target: Nid, inp_index: usize, with: Nid) -> Nid { self.remove_node_lookup(target); - debug_assert_ne!(self[target].inputs[inp_index], with); + debug_assert_ne!(self[target].inputs[inp_index], with, "{:?}", self[target]); let prev = self[target].inputs[inp_index]; self[target].inputs[inp_index] = with; @@ -1040,6 +1095,10 @@ impl Kind { fn ends_basic_block(&self) -> bool { matches!(self, Self::Return | Self::If | Self::End) } + + fn is_peeped(&self) -> bool { + !matches!(self, Self::End | Self::Arg) + } } impl fmt::Display for Kind { @@ -4735,5 +4794,6 @@ mod tests { pointer_opts; conditional_stores; loop_stores; + dead_code_in_loop; } } diff --git a/lang/src/vc.rs b/lang/src/vc.rs index 0f7cfeb..cacf136 100644 --- a/lang/src/vc.rs +++ b/lang/src/vc.rs @@ -287,15 +287,6 @@ impl BitSet { self.data.resize(new_len, 0); } - pub fn unset(&mut self, idx: Nid) -> bool { - let idx = idx as usize; - let data_idx = idx / Self::ELEM_SIZE; - let sub_idx = idx % Self::ELEM_SIZE; - let prev = self.data[data_idx] & (1 << sub_idx); - self.data[data_idx] &= !(1 << sub_idx); - prev != 0 - } - pub fn set(&mut self, idx: Nid) -> bool { let idx = idx as usize; let data_idx = idx / Self::ELEM_SIZE; diff --git a/lang/tests/son_tests_dead_code_in_loop.txt b/lang/tests/son_tests_dead_code_in_loop.txt new file mode 100644 index 0000000..e10b421 --- /dev/null +++ b/lang/tests/son_tests_dead_code_in_loop.txt @@ -0,0 +1,6 @@ +main: + LI64 r1, 0d + JALA r0, r31, 0a +code size: 29 +ret: 0 +status: Ok(())