fix ternary if (#250)

Use store and load to handle if expression as the blocks might be changed when generating sub-expressions.

Reviewed-on: M-Labs/nac3#250
Co-authored-by: ychenfo <yc@m-labs.hk>
Co-committed-by: ychenfo <yc@m-labs.hk>

nac3core/src/codegen/expr.rs

@@ -1226,21 +1226,44 @@ pub fn gen_expr<'ctx, 'a, G: CodeGenerator>(
                 .unwrap()
                 .to_basic_value_enum(ctx, generator)?
                 .into_int_value();
+            let body_ty = body.custom.unwrap();
+            let is_none = ctx.unifier.get_representative(body_ty) == ctx.primitives.none;
+            let result = if !is_none {
+                let llvm_ty = ctx.get_llvm_type(generator, body_ty);
+                Some(ctx.builder.build_alloca(llvm_ty, "if_exp_result"))
+            } else {
+                None
+            };
             let current = ctx.builder.get_insert_block().unwrap().get_parent().unwrap();
             let then_bb = ctx.ctx.append_basic_block(current, "then");
             let else_bb = ctx.ctx.append_basic_block(current, "else");
             let cont_bb = ctx.ctx.append_basic_block(current, "cont");
             ctx.builder.build_conditional_branch(test, then_bb, else_bb);
             ctx.builder.position_at_end(then_bb);
-            let a = generator.gen_expr(ctx, body)?.unwrap().to_basic_value_enum(ctx, generator)?;
+            let a = generator.gen_expr(ctx, body)?;
+            match result {
+                None => None,
+                Some(v) => {
+                    let a = a.unwrap().to_basic_value_enum(ctx, generator)?;
+                    Some(ctx.builder.build_store(v, a))
+                }
+            };
             ctx.builder.build_unconditional_branch(cont_bb);
             ctx.builder.position_at_end(else_bb);
-            let b = generator.gen_expr(ctx, orelse)?.unwrap().to_basic_value_enum(ctx, generator)?;
+            let b = generator.gen_expr(ctx, orelse)?;
+            match result {
+                None => None,
+                Some(v) => {
+                    let b = b.unwrap().to_basic_value_enum(ctx, generator)?;
+                    Some(ctx.builder.build_store(v, b))
+                }
+            };
             ctx.builder.build_unconditional_branch(cont_bb);
             ctx.builder.position_at_end(cont_bb);
-            let phi = ctx.builder.build_phi(a.get_type(), "ifexpr");
+            match result {
-            phi.add_incoming(&[(&a, then_bb), (&b, else_bb)]);
+                None => return Ok(None),
-            phi.as_basic_value().into()
+                Some(v) => return Ok(Some(ctx.builder.build_load(v, "if_exp_val_load").into()))
+            }
         }
         ExprKind::Call { func, args, keywords } => {
             let mut params = args

nac3core/src/codegen/test.rs

@@ -185,8 +185,17 @@ fn test_primitives() {
             init:
               %add = add i32 %0, %1
               %cmp = icmp eq i32 %add, 1
-              %ifexpr = select i1 %cmp, i32 %0, i32 0
+              br i1 %cmp, label %then, label %else
-              ret i32 %ifexpr
+            
+            then:                                             ; preds = %init
+              br label %cont
+            
+            else:                                             ; preds = %init
+              br label %cont
+            
+            cont:                                             ; preds = %else, %then
+              %if_exp_result.0 = phi i32 [ %0, %then ], [ 0, %else ]
+              ret i32 %if_exp_result.0
             }
        "}
         .trim();