chore(ssa refactor): Remove extra 'enable_side_effects' instructions (#…

…1828) Remove extra 'enable_side_effects' instructions
noir-lang · Jun 26, 2023 · 22be6be · 22be6be
1 parent e068fd4
commit 22be6be
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git a/crates/noirc_evaluator/src/ssa_refactor/ir/dfg.rs b/crates/noirc_evaluator/src/ssa_refactor/ir/dfg.rs
@@ -139,7 +139,7 @@ impl DataFlowGraph {
         ctrl_typevars: Option<Vec<Type>>,
     ) -> InsertInstructionResult {
         use InsertInstructionResult::*;
-        match instruction.simplify(self) {
+        match instruction.simplify(self, block) {
             SimplifyResult::SimplifiedTo(simplification) => SimplifiedTo(simplification),
             SimplifyResult::Remove => InstructionRemoved,
             SimplifyResult::None => {
@@ -371,6 +371,12 @@ impl std::ops::Index<InstructionId> for DataFlowGraph {
     }
 }
 
+impl std::ops::IndexMut<InstructionId> for DataFlowGraph {
+    fn index_mut(&mut self, id: InstructionId) -> &mut Self::Output {
+        &mut self.instructions[id]
+    }
+}
+
 impl std::ops::Index<ValueId> for DataFlowGraph {
     type Output = Value;
     fn index(&self, id: ValueId) -> &Self::Output {
@@ -387,7 +393,7 @@ impl std::ops::Index<BasicBlockId> for DataFlowGraph {
 
 impl std::ops::IndexMut<BasicBlockId> for DataFlowGraph {
     /// Get a mutable reference to a function's basic block for the given id.
-    fn index_mut(&mut self, id: BasicBlockId) -> &mut BasicBlock {
+    fn index_mut(&mut self, id: BasicBlockId) -> &mut Self::Output {
         &mut self.blocks[id]
     }
 }

diff --git a/crates/noirc_evaluator/src/ssa_refactor/ir/instruction.rs b/crates/noirc_evaluator/src/ssa_refactor/ir/instruction.rs
@@ -237,7 +237,10 @@ impl Instruction {
 
     /// Try to simplify this instruction. If the instruction can be simplified to a known value,
     /// that value is returned. Otherwise None is returned.
-    pub(crate) fn simplify(&self, dfg: &mut DataFlowGraph) -> SimplifyResult {
+    ///
+    /// The `block` parameter indicates the block this new instruction will be inserted into
+    /// after this call.
+    pub(crate) fn simplify(&self, dfg: &mut DataFlowGraph, block: BasicBlockId) -> SimplifyResult {
         use SimplifyResult::*;
         match self {
             Instruction::Binary(binary) => binary.simplify(dfg),
@@ -309,10 +312,19 @@ impl Instruction {
                 }
             }
             Instruction::Call { func, arguments } => simplify_call(*func, arguments, dfg),
+            Instruction::EnableSideEffects { condition } => {
+                if let Some(last) = dfg[block].instructions().last().copied() {
+                    let last = &mut dfg[last];
+                    if matches!(last, Instruction::EnableSideEffects { .. }) {
+                        *last = Instruction::EnableSideEffects { condition: *condition };
+                        return Remove;
+                    }
+                }
+                None
+            }
             Instruction::Allocate { .. } => None,
             Instruction::Load { .. } => None,
             Instruction::Store { .. } => None,
-            Instruction::EnableSideEffects { .. } => None,
         }
     }
 }