Remove branch isolation (#1353)

* remove branch isolation

* update book, add changelog

* clippy

* revert clippy suggestion

* move clippy allow rule to root lib.rs

* derive default

changelogs/unreleased/1353-dark64

@@ -0,0 +1 @@
+Remove expensive and buggy branch isolation

zokrates_analysis/src/lib.rs

@@ -6,7 +6,6 @@
 
 mod assembly_transformer;
 mod boolean_array_comparator;
-mod branch_isolator;
 mod condition_redefiner;
 mod constant_argument_checker;
 mod constant_resolver;
@@ -25,7 +24,6 @@ mod variable_write_remover;
 mod zir_propagation;
 
 use self::boolean_array_comparator::BooleanArrayComparator;
-use self::branch_isolator::Isolator;
 use self::condition_redefiner::ConditionRedefiner;
 use self::constant_argument_checker::ConstantArgumentChecker;
 use self::flatten_complex_types::Flattener;
@@ -132,17 +130,6 @@ pub fn analyse<'ast, T: Field>(
  let r = ConstantResolver::inline(p);
  log::trace!("\n{}", r);
 
- // isolate branches
- let r = if config.isolate_branches {
- log::debug!("Static analyser: Isolate branches");
- let r = Isolator::isolate(r);
- log::trace!("\n{}", r);
- r
- } else {
- log::debug!("Static analyser: Branch isolation skipped");
- r
- };
-
  // include logs
  let r = if config.debug {
  log::debug!("Static analyser: Include logs");

zokrates_ast/src/ir/mod.rs

@@ -74,7 +74,7 @@ impl<T: Field> fmt::Display for ConstraintStatement<T> {
  self.error
  .as_ref()
  .map(|e| format!(" // {}", e))
- .unwrap_or_else(|| "".to_string())
+ .unwrap_or_default()
  )
  }
 }

zokrates_ast/src/lib.rs

@@ -1,3 +1,6 @@
+// see https://github.com/mcarton/rust-derivative/issues/115
+#![allow(clippy::incorrect_partial_ord_impl_on_ord_type)]
+
 pub mod common;
 pub mod flat;
 pub mod ir;

zokrates_ast/src/untyped/mod.rs

@@ -543,11 +543,8 @@ impl<'ast> fmt::Display for Range<'ast> {
  self.from
  .as_ref()
  .map(|e| e.to_string())
- .unwrap_or_else(|| "".to_string()),
- self.to
- .as_ref()
- .map(|e| e.to_string())
- .unwrap_or_else(|| "".to_string())
+ .unwrap_or_default(),
+ self.to.as_ref().map(|e| e.to_string()).unwrap_or_default()
  )
  }
 }

zokrates_book/src/language/control_flow.md

@@ -47,9 +47,8 @@ Now the two caveats:
 ```zokrates
 {{#include ../../../zokrates_cli/examples/book/conditional_panic.zok}}
 ```
-The experimental flag `--branch-isolation` can be activated in the CLI in order to restrict any unsatisfied constraint to make the execution fail only if it is in a logically executed branch. This way, the execution of the program above will always succeed.
 
->The reason for these caveats is that the program is compiled down to an arithmetic circuit. This construct does not support jumping to a branch depending on a condition as you could do on traditional architectures. Instead, all branches are inlined as if they were printed on a circuit board. The `branch-isolation` feature comes with overhead for each assertion in each branch, and this overhead compounds when deeply nesting conditionals.
+>The reason for these caveats is that the program is compiled down to an arithmetic circuit. This construct does not support jumping to a branch depending on a condition as you could do on traditional architectures. Instead, all branches are inlined as if they were printed on a circuit board.
 
 ### For loops
 

zokrates_cli/src/ops/check.rs

@@ -44,11 +44,6 @@ pub fn subcommand() -> App<'static, 'static> {
  .possible_values(cli_constants::CURVES)
  .default_value(BN128),
  )
- .arg(Arg::with_name("isolate-branches")
- .long("isolate-branches")
- .help("Isolate the execution of branches: a panic in a branch only makes the program panic if this branch is being logically executed")
- .required(false)
- )
 }
 
 pub fn exec(sub_matches: &ArgMatches) -> Result<(), String> {
@@ -94,17 +89,13 @@ fn cli_check<T: Field>(sub_matches: &ArgMatches) -> Result<(), String> {
  )),
  }?;
 
- let config =
- CompileConfig::default().isolate_branches(sub_matches.is_present("isolate-branches"));
-
+ let config = CompileConfig::default();
  let resolver = FileSystemResolver::with_stdlib_root(stdlib_path);
+
  check::<T, _>(source, path, Some(&resolver), &config).map_err(|e| {
  format!(
  "Check failed:\n\n{}",
- e.0.iter()
- .map(|e| fmt_error(e))
- .collect::<Vec<_>>()
- .join("\n\n")
+ e.0.iter().map(fmt_error).collect::<Vec<_>>().join("\n\n")
  )
  })?;
 

zokrates_cli/src/ops/compile.rs

@@ -18,62 +18,71 @@ use zokrates_fs_resolver::FileSystemResolver;
 pub fn subcommand() -> App<'static, 'static> {
  SubCommand::with_name("compile")
  .about("Compiles into a runnable constraint system")
- .arg(Arg::with_name("input")
- .short("i")
- .long("input")
- .help("Path of the source code")
- .value_name("FILE")
- .takes_value(true)
- .required(true)
- ).arg(Arg::with_name("stdlib-path")
- .long("stdlib-path")
- .help("Path to the standard library")
- .value_name("PATH")
- .takes_value(true)
- .required(false)
- .env("ZOKRATES_STDLIB")
- .default_value(cli_constants::DEFAULT_STDLIB_PATH.as_str())
- ).arg(Arg::with_name("abi-spec")
- .short("s")
- .long("abi-spec")
- .help("Path of the ABI specification")
- .value_name("FILE")
- .takes_value(true)
- .required(false)
- .default_value(cli_constants::ABI_SPEC_DEFAULT_PATH)
- ).arg(Arg::with_name("output")
- .short("o")
- .long("output")
- .help("Path of the output binary")
- .value_name("FILE")
- .takes_value(true)
- .required(false)
- .default_value(cli_constants::FLATTENED_CODE_DEFAULT_PATH)
- ).arg(Arg::with_name("r1cs")
- .short("r1cs")
- .long("r1cs")
- .help("Path of the output r1cs file")
- .value_name("FILE")
- .takes_value(true)
- .required(false)
- .default_value(cli_constants::CIRCOM_R1CS_DEFAULT_PATH)
-).arg(Arg::with_name("curve")
- .short("c")
- .long("curve")
- .help("Curve to be used in the compilation")
- .takes_value(true)
- .required(false)
- .possible_values(cli_constants::CURVES)
- .default_value(BN128)
- ).arg(Arg::with_name("isolate-branches")
- .long("isolate-branches")
- .help("Isolate the execution of branches: a panic in a branch only makes the program panic if this branch is being logically executed")
- .required(false)
- ).arg(Arg::with_name("debug")
- .long("debug")
- .help("Include logs")
- .required(false)
-)
+ .arg(
+ Arg::with_name("input")
+ .short("i")
+ .long("input")
+ .help("Path of the source code")
+ .value_name("FILE")
+ .takes_value(true)
+ .required(true),
+ )
+ .arg(
+ Arg::with_name("stdlib-path")
+ .long("stdlib-path")
+ .help("Path to the standard library")
+ .value_name("PATH")
+ .takes_value(true)
+ .required(false)
+ .env("ZOKRATES_STDLIB")
+ .default_value(cli_constants::DEFAULT_STDLIB_PATH.as_str()),
+ )
+ .arg(
+ Arg::with_name("abi-spec")
+ .short("s")
+ .long("abi-spec")
+ .help("Path of the ABI specification")
+ .value_name("FILE")
+ .takes_value(true)
+ .required(false)
+ .default_value(cli_constants::ABI_SPEC_DEFAULT_PATH),
+ )
+ .arg(
+ Arg::with_name("output")
+ .short("o")
+ .long("output")
+ .help("Path of the output binary")
+ .value_name("FILE")
+ .takes_value(true)
+ .required(false)
+ .default_value(cli_constants::FLATTENED_CODE_DEFAULT_PATH),
+ )
+ .arg(
+ Arg::with_name("r1cs")
+ .short("r1cs")
+ .long("r1cs")
+ .help("Path of the output r1cs file")
+ .value_name("FILE")
+ .takes_value(true)
+ .required(false)
+ .default_value(cli_constants::CIRCOM_R1CS_DEFAULT_PATH),
+ )
+ .arg(
+ Arg::with_name("curve")
+ .short("c")
+ .long("curve")
+ .help("Curve to be used in the compilation")
+ .takes_value(true)
+ .required(false)
+ .possible_values(cli_constants::CURVES)
+ .default_value(BN128),
+ )
+ .arg(
+ Arg::with_name("debug")
+ .long("debug")
+ .help("Include logs")
+ .required(false),
+ )
 }
 
 pub fn exec(sub_matches: &ArgMatches) -> Result<(), String> {
@@ -124,10 +133,7 @@ fn cli_compile<T: Field>(sub_matches: &ArgMatches) -> Result<(), String> {
  )),
  }?;
 
- let config = CompileConfig::default()
- .isolate_branches(sub_matches.is_present("isolate-branches"))
- .debug(sub_matches.is_present("debug"));
-
+ let config = CompileConfig::default().debug(sub_matches.is_present("debug"));
  let resolver = FileSystemResolver::with_stdlib_root(stdlib_path);
 
  log::debug!("Compile");
@@ -138,10 +144,7 @@ fn cli_compile<T: Field>(sub_matches: &ArgMatches) -> Result<(), String> {
  .map_err(|e| {
  format!(
  "Compilation failed:\n\n{}",
- e.0.iter()
- .map(|e| fmt_error(e))
- .collect::<Vec<_>>()
- .join("\n\n")
+ e.0.iter().map(fmt_error).collect::<Vec<_>>().join("\n\n")
  )
  })?;