From ba12cba6e5c8d31a5d5610f9f0768a6b89db7c73 Mon Sep 17 00:00:00 2001
From: Ary Borenszweig <asterite@gmail.com>
Date: Sat, 12 Apr 2025 08:15:23 -0300
Subject: [PATCH] chore: parse IfElse in SSA parser

---
 .../noirc_evaluator/src/ssa/parser/ast.rs     |  7 +++++++
 .../src/ssa/parser/into_ssa.rs                | 16 ++++++++++++++++
 .../noirc_evaluator/src/ssa/parser/mod.rs     | 19 +++++++++++++++++++
 .../noirc_evaluator/src/ssa/parser/tests.rs   | 12 ++++++++++++
 .../noirc_evaluator/src/ssa/parser/token.rs   |  3 +++
 5 files changed, 57 insertions(+)

diff --git a/compiler/noirc_evaluator/src/ssa/parser/ast.rs b/compiler/noirc_evaluator/src/ssa/parser/ast.rs
index 10ffe8a6be3..504ab0ff107 100644
--- a/compiler/noirc_evaluator/src/ssa/parser/ast.rs
+++ b/compiler/noirc_evaluator/src/ssa/parser/ast.rs
@@ -121,6 +121,13 @@ pub(crate) enum ParsedInstruction {
     EnableSideEffectsIf {
         condition: ParsedValue,
     },
+    IfElse {
+        target: Identifier,
+        then_condition: ParsedValue,
+        then_value: ParsedValue,
+        else_condition: ParsedValue,
+        else_value: ParsedValue,
+    },
     IncrementRc {
         value: ParsedValue,
     },
diff --git a/compiler/noirc_evaluator/src/ssa/parser/into_ssa.rs b/compiler/noirc_evaluator/src/ssa/parser/into_ssa.rs
index 8420cd272ad..d794aa235d1 100644
--- a/compiler/noirc_evaluator/src/ssa/parser/into_ssa.rs
+++ b/compiler/noirc_evaluator/src/ssa/parser/into_ssa.rs
@@ -297,6 +297,22 @@ impl Translator {
                 let condition = self.translate_value(condition)?;
                 self.builder.insert_enable_side_effects_if(condition);
             }
+            ParsedInstruction::IfElse {
+                target,
+                then_condition,
+                then_value,
+                else_condition,
+                else_value,
+            } => {
+                let then_condition = self.translate_value(then_condition)?;
+                let then_value = self.translate_value(then_value)?;
+                let else_condition = self.translate_value(else_condition)?;
+                let else_value = self.translate_value(else_value)?;
+                let instruction =
+                    Instruction::IfElse { then_condition, then_value, else_condition, else_value };
+                let value_id = self.builder.insert_instruction(instruction, None).first();
+                self.define_variable(target, value_id)?;
+            }
             ParsedInstruction::IncrementRc { value } => {
                 let value = self.translate_value(value)?;
                 self.builder.increment_array_reference_count(value);
diff --git a/compiler/noirc_evaluator/src/ssa/parser/mod.rs b/compiler/noirc_evaluator/src/ssa/parser/mod.rs
index 89cbb99313f..ad3d72d24eb 100644
--- a/compiler/noirc_evaluator/src/ssa/parser/mod.rs
+++ b/compiler/noirc_evaluator/src/ssa/parser/mod.rs
@@ -551,6 +551,25 @@ impl<'a> Parser<'a> {
             return Ok(ParsedInstruction::Truncate { target, value, bit_size, max_bit_size });
         }
 
+        if self.eat_keyword(Keyword::If)? {
+            let then_condition = self.parse_value_or_error()?;
+            self.eat_or_error(Token::Keyword(Keyword::Then))?;
+            let then_value = self.parse_value_or_error()?;
+            self.eat_or_error(Token::Keyword(Keyword::Else))?;
+            self.eat_or_error(Token::LeftParen)?;
+            self.eat_or_error(Token::Keyword(Keyword::If))?;
+            let else_condition = self.parse_value_or_error()?;
+            self.eat_or_error(Token::RightParen)?;
+            let else_value = self.parse_value_or_error()?;
+            return Ok(ParsedInstruction::IfElse {
+                target,
+                then_condition,
+                then_value,
+                else_condition,
+                else_value,
+            });
+        }
+
         if let Some(op) = self.eat_binary_op()? {
             let lhs = self.parse_value_or_error()?;
             self.eat_or_error(Token::Comma)?;
diff --git a/compiler/noirc_evaluator/src/ssa/parser/tests.rs b/compiler/noirc_evaluator/src/ssa/parser/tests.rs
index 864f2ab77e5..ff83b150f73 100644
--- a/compiler/noirc_evaluator/src/ssa/parser/tests.rs
+++ b/compiler/noirc_evaluator/src/ssa/parser/tests.rs
@@ -610,3 +610,15 @@ fn parses_purity() {
     ";
     assert_ssa_roundtrip(src);
 }
+
+#[test]
+fn test_parses_if_else() {
+    let src = "
+        acir(inline) fn main f0 {
+          b0(v0: u1, v1: u1):
+            v4 = if v0 then Field 1 else (if v1) Field 2
+            return v4
+        }
+        ";
+    assert_ssa_roundtrip(src);
+}
diff --git a/compiler/noirc_evaluator/src/ssa/parser/token.rs b/compiler/noirc_evaluator/src/ssa/parser/token.rs
index abd834c8cc3..0c4b60cc3ea 100644
--- a/compiler/noirc_evaluator/src/ssa/parser/token.rs
+++ b/compiler/noirc_evaluator/src/ssa/parser/token.rs
@@ -139,6 +139,7 @@ pub(crate) enum Keyword {
     Fold,
     Fn,
     Function,
+    If,
     Impure,
     IncRc,
     Index,
@@ -196,6 +197,7 @@ impl Keyword {
             "else" => Keyword::Else,
             "enable_side_effects" => Keyword::EnableSideEffects,
             "eq" => Keyword::Eq,
+            "if" => Keyword::If,
             "impure" => Keyword::Impure,
             "inline" => Keyword::Inline,
             "inline_always" => Keyword::InlineAlways,
@@ -267,6 +269,7 @@ impl Display for Keyword {
             Keyword::Fold => write!(f, "fold"),
             Keyword::Fn => write!(f, "fn"),
             Keyword::Function => write!(f, "function"),
+            Keyword::If => write!(f, "if"),
             Keyword::Impure => write!(f, "impure"),
             Keyword::IncRc => write!(f, "inc_rc"),
             Keyword::Index => write!(f, "index"),