From 02f896ed7d1a088def0d12c7a55a6f67c034ab21 Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Mon, 28 Dec 2020 18:01:13 -0700
Subject: implement while loops

---
 crowbar_reference_compiler/ast.py    |  7 +++++++
 crowbar_reference_compiler/ssagen.py | 23 ++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/crowbar_reference_compiler/ast.py b/crowbar_reference_compiler/ast.py
index 142fa8e..7ae7ff9 100644
--- a/crowbar_reference_compiler/ast.py
+++ b/crowbar_reference_compiler/ast.py
@@ -531,6 +531,13 @@ class ASTBuilder(NodeVisitor):
             assert kwd.type == 'else'
         return IfStatement(condition, then, els)
 
+    def visit_WhileStatement(self, node, visited_children):
+        kwd, lparen, condition, rparen, body = visited_children
+        assert kwd.type == 'while'
+        assert lparen.type == '('
+        assert rparen.type == ')'
+        return WhileStatement(condition, body)
+
     def visit_ReturnStatement(self, node, visited_children):
         ret, body, semi = visited_children
         assert ret.type == 'return'
diff --git a/crowbar_reference_compiler/ssagen.py b/crowbar_reference_compiler/ssagen.py
index 5212440..c71ddc4 100644
--- a/crowbar_reference_compiler/ssagen.py
+++ b/crowbar_reference_compiler/ssagen.py
@@ -7,7 +7,8 @@ from .ast import ImplementationFile, FunctionDefinition, ExpressionStatement, Fu
     VariableExpression, ConstantExpression, ReturnStatement, BasicType, IfStatement, ComparisonExpression, \
     AddExpression, StructPointerElementExpression, Declaration, PointerType, StructDeclaration, VariableDefinition, \
     MultiplyExpression, LogicalNotExpression, DirectAssignment, UpdateAssignment, SizeofExpression, Expression, \
-    ConstType, ArrayIndexExpression, ArrayType, NegativeExpression, SubtractExpression, AddressOfExpression
+    ConstType, ArrayIndexExpression, ArrayType, NegativeExpression, SubtractExpression, AddressOfExpression, \
+    WhileStatement
 
 
 @dataclass
@@ -181,6 +182,26 @@ def _(target: IfStatement, context: CompileContext) -> SsaResult:
     return result
 
 
+@compile_to_ssa.register
+def _(target: WhileStatement, context: CompileContext) -> SsaResult:
+    start_label = context.next_label
+    context.next_label += 1
+    result = SsaResult([], [f"@l{start_label}"])
+    body_label = context.next_label
+    context.next_label += 1
+    end_label = context.next_label
+    context.next_label += 1
+    result += compile_to_ssa(target.condition, context)
+    condition_dest = context.next_temp - 1
+    result.code.append(f"jnz %t{condition_dest}, @l{body_label}, @l{end_label}")
+    result.code.append(f"@l{body_label}")
+    for statement in target.body:
+        result += compile_to_ssa(statement, context)
+    result.code.append(f"jmp @l{start_label}")
+    result.code.append(f"@l{end_label}")
+    return result
+
+
 @compile_to_ssa.register
 def _(target: ComparisonExpression, context: CompileContext) -> SsaResult:
     result = compile_to_ssa(target.value1, context)
-- 
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