chore: Remove resolve_is_unconstrained pass

compiler/noirc_evaluator/src/ssa.rs

@@ -153,7 +153,6 @@ fn optimize_all(builder: SsaBuilder, options: &SsaEvaluatorOptions) -> Result<Ss
         .run_pass(Ssa::remove_unreachable_functions, "Removing Unreachable Functions")
         .run_pass(Ssa::defunctionalize, "Defunctionalization")
         .run_pass(Ssa::remove_paired_rc, "Removing Paired rc_inc & rc_decs")
-        .run_pass(Ssa::resolve_is_unconstrained, "Resolving IsUnconstrained")
         .run_pass(|ssa| ssa.inline_functions(options.inliner_aggressiveness), "Inlining (1st)")
         // Run mem2reg with the CFG separated into blocks
         .run_pass(Ssa::mem2reg, "Mem2Reg (1st)")

compiler/noirc_evaluator/src/ssa/ir/dfg.rs

@@ -470,6 +470,7 @@ impl DataFlowGraph {
 
     /// Remove an instruction by replacing it with a `Noop` instruction.
     /// Doing this avoids shifting over each instruction after this one in its block's instructions vector.
+    #[allow(unused)]
     pub(crate) fn remove_instruction(&mut self, instruction: InstructionId) {
         self.instructions[instruction] = Instruction::Noop;
         self.results.insert(instruction, smallvec::SmallVec::new());

compiler/noirc_evaluator/src/ssa/ir/instruction/call.rs

@@ -331,7 +331,10 @@ pub(super) fn simplify_call(
             simplify_black_box_func(bb_func, arguments, dfg, block, call_stack)
         }
         Intrinsic::AsWitness => SimplifyResult::None,
-        Intrinsic::IsUnconstrained => SimplifyResult::None,
+        Intrinsic::IsUnconstrained => {
+            let result = dfg.runtime().is_brillig().into();
+            SimplifyResult::SimplifiedTo(dfg.make_constant(result, NumericType::bool()))
+        }
         Intrinsic::DerivePedersenGenerators => {
             if let Some(Type::Array(_, len)) = return_type.clone() {
                 simplify_derive_generators(dfg, arguments, len, block, call_stack)

compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs

@@ -1557,7 +1557,6 @@ mod test {
         // After EnableSideEffectsIf removal:
         brillig(inline) fn main f0 {
           b0(v0: Field, v1: Field, v2: u1):
-            v4 = call is_unconstrained() -> u1
             v7 = call to_be_radix(v0, u32 256) -> [u8; 1]    // `a.to_be_radix(256)`;
             inc_rc v7
             v8 = call to_be_radix(v0, u32 256) -> [u8; 1]    // duplicate load of `a`
@@ -1574,14 +1573,13 @@ mod test {
         let expected = "
         brillig(inline) fn main f0 {
           b0(v0: Field, v1: Field, v2: u1):
-            v4 = call is_unconstrained() -> u1
-            v7 = call to_be_radix(v0, u32 256) -> [u8; 1]
-            inc_rc v7
-            inc_rc v7
-            v8 = cast v2 as Field
-            v9 = mul v0, v8
-            v10 = call to_be_radix(v9, u32 256) -> [u8; 1]
-            inc_rc v10
+            v5 = call to_be_radix(v0, u32 256) -> [u8; 1]
+            inc_rc v5
+            inc_rc v5
+            v6 = cast v2 as Field
+            v7 = mul v0, v6
+            v8 = call to_be_radix(v7, u32 256) -> [u8; 1]
+            inc_rc v8
             enable_side_effects v2
             return
         }

compiler/noirc_evaluator/src/ssa/opt/mod.rs

@@ -21,7 +21,6 @@ mod remove_bit_shifts;
 mod remove_enable_side_effects;
 mod remove_if_else;
 mod remove_unreachable;
-mod resolve_is_unconstrained;
 mod simplify_cfg;
 mod unrolling;