WASM: Support visit_StringLen()

src/libasr/codegen/asr_to_wasm.cpp

@@ -77,7 +77,8 @@ enum RT_FUNCS {
     abs_c64 = 10,
     equal_c32 = 11,
     equal_c64 = 12,
-    NO_OF_RT_FUNCS = 13,
+    str_len = 13,
+    NO_OF_RT_FUNCS = 14,
 };
 
 enum GLOBAL_VAR {
@@ -552,6 +553,14 @@ class ASRToWASMVisitor : public ASR::BaseVisitor<ASRToWASMVisitor> {
         });
     }
 
+    void emit_str_len() {
+        using namespace wasm;
+        m_wa.define_func({i32}, {i32}, {}, "str_len", [&](){
+            m_wa.emit_local_get(0);
+            m_wa.emit_i32_load(wasm::mem_align::b8, 4);
+        });
+    }
+
     void declare_global_var(ASR::Variable_t* v) {
         if (v->m_type->type == ASR::ttypeType::TypeParameter) {
             // Ignore type variables
@@ -688,6 +697,7 @@ class ASRToWASMVisitor : public ASR::BaseVisitor<ASRToWASMVisitor> {
         m_rt_funcs_map[abs_c64] = &ASRToWASMVisitor::emit_complex_abs_64;
         m_rt_funcs_map[equal_c32] = &ASRToWASMVisitor::emit_complex_equal_32;
         m_rt_funcs_map[equal_c64] = &ASRToWASMVisitor::emit_complex_equal_64;
+        m_rt_funcs_map[str_len] = &ASRToWASMVisitor::emit_str_len;
 
         {
             // Pre-declare all functions first, then generate code
@@ -1935,6 +1945,16 @@ class ASRToWASMVisitor : public ASR::BaseVisitor<ASRToWASMVisitor> {
         throw CodeGenError("String Types not yet supported");
     }
 
+    void visit_StringLen(const ASR::StringLen_t & x) {
+        if (x.m_value) {
+            visit_expr(*x.m_value);
+            return;
+        }
+        INCLUDE_RUNTIME_FUNC(str_len);
+        this->visit_expr(*x.m_arg);
+        m_wa.emit_call(m_rt_func_used_idx[str_len]);
+    }
+
     void visit_LogicalBinOp(const ASR::LogicalBinOp_t &x) {
         if (x.m_value) {
             visit_expr(*x.m_value);