Remove unused locals (FuelLabs#4458)

sway-ir/src/function.rs

@@ -398,6 +398,15 @@ impl Function {
         context.functions[self.0].local_storage.iter()
     }
 
+    /// Remove given list of locals
+    pub fn remove_locals(&self, context: &mut Context, removals: &Vec<String>) {
+        for remove in removals {
+            if let Some(local) = context.functions[self.0].local_storage.remove(remove) {
+                context.local_vars.remove(local.0);
+            }
+        }
+    }
+
     /// Merge values from another [`Function`] into this one.
     ///
     /// The names of the merged values are guaranteed to be unique via the use of

sway-ir/src/optimize/dce.rs

@@ -6,8 +6,8 @@
 //! This pass does not do CFG transformations. That is handled by simplify_cfg.
 
 use crate::{
-    AnalysisResults, Block, Context, Function, Instruction, IrError, Module, Pass, PassMutability,
-    ScopedPass, Value, ValueDatum,
+    AnalysisResults, Block, Context, Function, Instruction, IrError, LocalVar, Module, Pass,
+    PassMutability, ScopedPass, Value, ValueDatum,
 };
 
 use std::collections::{HashMap, HashSet};
@@ -47,10 +47,18 @@ pub fn dce(
 ) -> Result<bool, IrError> {
     // Number of uses that an instruction has.
     let mut num_uses: HashMap<Value, (Block, u32)> = HashMap::new();
+    let mut num_local_uses: HashMap<LocalVar, u32> = HashMap::new();
 
     // Go through each instruction and update use_count.
     for (block, inst) in function.instruction_iter(context) {
-        let opds = inst.get_instruction(context).unwrap().get_operands();
+        let inst = inst.get_instruction(context).unwrap();
+        if let Instruction::GetLocal(local) = inst {
+            num_local_uses
+                .entry(*local)
+                .and_modify(|count| *count += 1)
+                .or_insert(1);
+        }
+        let opds = inst.get_operands();
         for v in opds {
             match context.values[v.0].value {
                 ValueDatum::Instruction(_) => {
@@ -94,7 +102,24 @@ pub fn dce(
         }
 
         in_block.remove_instruction(context, dead);
+
+        if let ValueDatum::Instruction(Instruction::GetLocal(local)) = context.values[dead.0].value
+        {
+            let count = num_local_uses.get_mut(&local).unwrap();
+            *count -= 1;
+        }
+        modified = true;
+    }
+
+    let local_removals: Vec<_> = function
+        .locals_iter(context)
+        .filter_map(|(name, local)| {
+            (num_local_uses.get(local).cloned().unwrap_or(0) == 0).then_some(name.clone())
+        })
+        .collect();
+    if !local_removals.is_empty() {
         modified = true;
+        function.remove_locals(context, &local_removals);
     }
 
     Ok(modified)

sway-ir/tests/dce/dce2.ir

@@ -0,0 +1,12 @@
+// regex: ID=[[:alpha:]0-9]+
+
+script {
+    fn main() -> bool {
+// not: local u64 i    
+        local u64 i
+
+        entry():
+        v9 = const bool false
+        ret bool v9
+    }
+}

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/array_of_structs_caller/src/main.sw

@@ -4,7 +4,7 @@ use array_of_structs_abi::{Id, TestContract, Wrapper};
 use std::hash::sha256;
 
 fn main() -> u64 {
-    let addr = abi(TestContract, 0xa5d354e58efd316c2eb3f4b273a2143e7d534952fae5e191e057b27403ae829e);
+    let addr = abi(TestContract, 0xfd87acbc9cfdbae40894dc1be15c8f5f07a5775ca110df2584f053ac6ad10672);
 
     let input = [Wrapper {
         id: Id {

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/call_basic_storage/src/main.sw

@@ -2,7 +2,7 @@ script;
 use basic_storage_abi::{BasicStorage, Quad};
 
 fn main() -> u64 {
-    let addr = abi(BasicStorage, 0xc98246b75472af9196be66b65a979ebbe5cd5975d1331f18ce2cda66a9819379);
+    let addr = abi(BasicStorage, 0x6906bdbccb7ca8e66c11ce16518c2f946da094d3e2c8561ca38d5a6d9a13e996);
     let key = 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff;
     let value = 4242;
 

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/call_contract_with_type_aliases/src/main.sw

@@ -3,7 +3,7 @@ script;
 use contract_with_type_aliases_abi::*;
 
 fn main() {
-    let caller = abi(MyContract, 0xaa380eacd28dbfba42ee88a1df59544f5cbc3e862a5b12bc2af894923ec4f5e8);
+    let caller = abi(MyContract, 0xf5030df8b9336a88f24afa90afe33aea6affd5295821aeb4eade84cd1fee4345);
 
     let x = AssetId::from(0x0101010101010101010101010101010101010101010101010101010101010101);
 

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/call_increment_contract/src/main.sw

@@ -3,7 +3,7 @@ script;
 use increment_abi::Incrementor;
 
 fn main() -> bool {
-    let the_abi = abi(Incrementor, 0xc9baa3acb84a53e91b31b2ecc514d5ad8a715083282dc16d520b5d40a9fc94a7);
+    let the_abi = abi(Incrementor, 0x6b259c454583b3995b9e35effa476f8cb2155ff44d1d8d567a83108b4fe65444);
     the_abi.increment(5);
     the_abi.increment(5);
     let result = the_abi.get();

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/caller_context_test/src/main.sw

@@ -7,7 +7,7 @@ fn main() -> bool {
     let zero = b256::min();
     let gas: u64 = u64::max();
     let amount: u64 = 11;
-    let other_contract_id = ContractId::from(0xc29171776f4d174a9e338d12c3b84e1de1694ba8bd64fb725d9eaf2842c7c6f1);
+    let other_contract_id = ContractId::from(0x338000acdb5764cdaaf90a70b2fa73c68fed43ce2b7bdb329d361cb6b5393a43);
     let base_asset_id = BASE_ASSET_ID;
 
     let test_contract = abi(ContextTesting, other_contract_id.into());

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/get_storage_key_caller/src/main.sw

@@ -3,7 +3,7 @@ script;
 use get_storage_key_abi::TestContract;
 
 fn main() -> u64 {
-    let caller = abi(TestContract, 0x79fd3f7662e227f8ff7bef65b683fa4417b7e9f6d6bdbc0eb4d899ea2d73cad3);
+    let caller = abi(TestContract, 0xfd77b8770d4b9ad2402e8d6c838c8a837d2a56dd02ec4445c4c212bfce66b143);
 
     // Get the storage keys directly by calling the contract methods from_f1,
     // from_f2, from_f3, from_f4. The keys correspond to different entries in

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/nested_struct_args_caller/src/main.sw

@@ -3,7 +3,7 @@ script;
 use nested_struct_args_abi::*;
 
 fn main() -> bool {
-    let contract_id = 0xc07c133be5867020f483c34e045c9162867d6b40accc022525e50c048d17d679;
+    let contract_id = 0x1ce4c30fc1fe5d4639683ad1330de7739efd297671a540ffe9012e9cf3953fe7;
     let caller = abi(NestedStructArgs, contract_id);
 
     let param_one = StructOne {

test/src/e2e_vm_tests/test_programs/should_pass/require_contract_deployment/storage_access_caller/src/main.sw

@@ -4,7 +4,7 @@ use storage_access_abi::*;
 use std::hash::sha256;
 
 fn main() -> bool {
-    let contract_id = 0x9ec7ac3cce15b1b75adabd598a374e96b606471a56229486a2d0ca26c08ed994;
+    let contract_id = 0x8982d742b1f313818d24516f7410519ca4fd4bbab470012809ffde710c45c0a4;
     let caller = abi(StorageAccess, contract_id);
 
     // Test initializers

test/src/ir_generation/tests/simple_contract_call.sw

@@ -48,7 +48,6 @@ fn main() -> u64 {
 // check: local b256 $(asset_id_2_const=$ID) = const b256 0x0000000000000000000000000000000000000000000000000000000000000000
 
 // check: local u64 a
-// check: local b256 arg_for_get_b256
 // check: local { u64, b256 } args_struct_for_get_s
 // check: local b256 b
 // check: local { u64, b256 } s