chore(ssa): Remove dead code + modify visibility of modules to match …

…usage (#786)

* make all modules not needed outside of SSA private

* Remove dead code

* document `as_u32` and link to issue about its soundness

crates/noirc_evaluator/src/ssa/context.rs

@@ -664,7 +664,7 @@ impl SsaContext {
             None
         }
     }
-    //blocks/////////////////////////
+
     pub fn try_get_block_mut(&mut self, id: BlockId) -> Option<&mut block::BasicBlock> {
         self.blocks.get_mut(id.0)
     }

crates/noirc_evaluator/src/ssa/integer.rs

@@ -442,7 +442,6 @@ fn get_load_max(
     max_map: &mut HashMap<NodeId, BigUint>,
     value_map: &HashMap<NodeId, NodeId>,
     array: ArrayId,
-    // obj_type: ObjectType,
 ) -> BigUint {
     if let Some(&value) = ctx.get_indexed_value(array, address) {
         return get_obj_max_value(ctx, value, max_map, value_map);

crates/noirc_evaluator/src/ssa/mem.rs

@@ -93,7 +93,10 @@ impl Memory {
         self.last_adr += len;
         id
     }
-
+    /// Coerces a FieldElement into a u32
+    /// By taking its value modulo 2^32
+    ///
+    /// See issue #785 on whether this is safe
     pub fn as_u32(value: FieldElement) -> u32 {
         let big_v = BigUint::from_bytes_be(&value.to_be_bytes());
         let mut modulus = BigUint::from(2_u32);

crates/noirc_evaluator/src/ssa/mod.rs

@@ -1,15 +1,15 @@
 pub mod acir_gen;
-pub mod anchor;
-pub mod block;
-pub mod builtin;
+mod anchor;
+mod block;
+mod builtin;
 pub mod code_gen;
-pub mod conditional;
-pub mod context;
-pub mod flatten;
-pub mod function;
-pub mod inline;
-pub mod integer;
-pub mod mem;
+mod conditional;
+mod context;
+mod flatten;
+mod function;
+mod inline;
+mod integer;
+mod mem;
 pub mod node;
-pub mod optimizations;
-pub mod ssa_form;
+mod optimizations;
+mod ssa_form;

crates/noirc_evaluator/src/ssa/node.rs

@@ -173,17 +173,12 @@ impl Variable {
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum ObjectType {
-    //Numeric(NumericType),
     NativeField,
-    // custom_field(BigUint), //TODO requires copy trait for BigUint
     Boolean,
     Unsigned(u32), //bit size
     Signed(u32),   //bit size
     Pointer(ArrayId),
-
     Function,
-    //TODO big_int
-    //TODO floats
     NotAnObject, //not an object
 }
 
@@ -497,7 +492,6 @@ pub enum Operation {
         root: NodeId,
         block_args: Vec<(NodeId, BlockId)>,
     },
-    //Call(function::FunctionCall),
     Call {
         func: NodeId,
         arguments: Vec<NodeId>,

crates/noirc_evaluator/src/ssa/optimizations.rs

@@ -107,7 +107,10 @@ fn evaluate_intrinsic(
         _ => todo!(),
     }
 }
-////////////////////CSE////////////////////////////////////////
+
+//
+// The following code will be concerned with Common Subexpression Elimination (CSE)
+//
 
 pub fn propagate(ctx: &SsaContext, id: NodeId, modified: &mut bool) -> NodeId {
     if let Some(obj) = ctx.try_get_instruction(id) {
@@ -409,7 +412,7 @@ fn cse_block_with_anchor(
     Ok(last)
 }
 
-pub fn is_some(ctx: &SsaContext, id: NodeId) -> bool {
+fn is_some(ctx: &SsaContext, id: NodeId) -> bool {
     if id == NodeId::dummy() {
         return false;
     }

crates/noirc_evaluator/src/ssa/ssa_form.rs

@@ -7,7 +7,7 @@ use crate::ssa::{
 use std::collections::HashSet;
 
 // create phi arguments from the predecessors of the block (containing phi)
-pub fn write_phi(ctx: &mut SsaContext, predecessors: &[BlockId], var: NodeId, phi: NodeId) {
+fn write_phi(ctx: &mut SsaContext, predecessors: &[BlockId], var: NodeId, phi: NodeId) {
     let mut result = Vec::new();
     for b in predecessors {
         let v = get_current_value_in_block(ctx, var, *b);
@@ -54,7 +54,7 @@ pub fn seal_block(ctx: &mut SsaContext, block_id: BlockId, entry_block: BlockId)
 }
 
 // write dummy store for join block
-pub fn add_dummy_store(ctx: &mut SsaContext, entry: BlockId, join: BlockId) {
+fn add_dummy_store(ctx: &mut SsaContext, entry: BlockId, join: BlockId) {
     //retrieve modified arrays
     let mut modified = HashSet::new();
     if entry == join {
@@ -74,7 +74,7 @@ pub fn add_dummy_store(ctx: &mut SsaContext, entry: BlockId, join: BlockId) {
 }
 
 //look-up recursively into predecessors
-pub fn get_block_value(ctx: &mut SsaContext, root: NodeId, block_id: BlockId) -> NodeId {
+fn get_block_value(ctx: &mut SsaContext, root: NodeId, block_id: BlockId) -> NodeId {
     let result = if !ctx.sealed_blocks.contains(&block_id) {
         //incomplete CFG
         ctx.generate_empty_phi(block_id, root)