Merge pull request #1290 from Thirumalai-Shaktivel/loop_stmt

Implement Loop statement

Author: certik

integration_tests/CMakeLists.txt

@@ -210,6 +210,9 @@ RUN(NAME expr_13             LABELS llvm c
         EXTRAFILES expr_13b.c)
 RUN(NAME expr_14             LABELS cpython llvm c)
 RUN(NAME loop_01             LABELS cpython llvm c)
+RUN(NAME loop_02             LABELS cpython llvm wasm wasm_x86)
+RUN(NAME if_01               LABELS cpython llvm wasm wasm_x86)
+RUN(NAME if_02               LABELS cpython llvm wasm wasm_x86)
 RUN(NAME print_02            LABELS cpython llvm)
 RUN(NAME test_types_01       LABELS cpython llvm c)
 RUN(NAME test_str_01         LABELS cpython llvm c)

integration_tests/if_01.py

@@ -1,45 +1,46 @@
 def Test_if_01():
+    z: i32 = 0
     if True:
-        print(1)
+        assert True
 
     if False:
-        print(0)
+        assert False
 
     if 1 < 0:
-        print(0)
+        assert False
     else:
-        print(1)
+        assert True
 
     if 1 > 0:
-        print(1)
+        assert True
     else:
-        print(0)
+        assert False
 
     if 1 < 0:
-        print(1)
+        assert False
     elif 1 > 0:
-        print(1)
+        assert True
     else:
-        print(0)
+        assert False
 
 def Test_if_02():
     if True:
         print(1)
         if True:
             print(2)
             if False:
-                print(3)
+                assert False
             elif True:
                 print(4)
             else:
-                print(5)
+                assert False
         else:
-            print(6)
+            assert False
 
     if True:
         print(7)
         if False:
-            print(8)
+            assert False
             if False:
                 print(9)
             else:
@@ -48,7 +49,7 @@ def Test_if_02():
             if True:
                 print(11)
             else:
-                print(12)
+                assert False
             print(13)
     print(14)
 

integration_tests/if_02.py

@@ -1,4 +1,4 @@
-from ltypes import bool, i32
+from ltypes import i32
 
 def test_if_01():
     x: bool = True
@@ -33,8 +33,7 @@ def test_if_01():
     if y >= 2:
         z += 1
 
-    # TODO: replace this an assert statement
-    print(z)
+    assert z == 9
 
 def verify():
     test_if_01()

integration_tests/loop_02.py

@@ -0,0 +1,84 @@
+from ltypes import i32
+def test_loop_01():
+    i: i32 = 0
+    j: i32 = 0
+
+    while False:
+        assert False
+
+    while i < 0:
+        assert False
+
+    while i < 10:
+        i += 1
+    assert i == 10
+
+    while i < 20:
+        while i < 15:
+            i += 1
+        i += 1
+    assert i == 20
+
+    for i in range(5):
+        assert i == j
+        j += 1
+
+def test_loop_02():
+    i: i32 = 0
+    j: i32 = 0
+
+    j = 0
+    for i in range(10, 0, -1):
+        j = j + i
+    assert j == 55
+
+    for i in range(5):
+        if i == 3:
+            break
+    assert i == 3
+
+    j = 0
+    for i in range(5):
+        if i == 3:
+            continue
+        j += 1
+    assert j == 4
+
+def test_loop_03():
+    i: i32 = 0
+    j: i32 = 0
+    k: i32 = 0
+    while i < 10:
+        j = 0
+        while j < 10:
+            k += 1
+            if i == 0:
+                if j == 3:
+                    continue
+                else:
+                    j += 1
+            j += 1
+        i += 1
+    assert k == 95
+
+    i = 0; j = 0; k = 0
+    while i < 10:
+        j = 0
+        while j < 10:
+            k += i + j
+            if i == 5:
+                if j == 4:
+                    break
+                else:
+                    j += 1
+            j += 1
+        i += 1
+    assert k == 826
+
+
+def verify():
+    test_loop_01()
+    test_loop_02()
+    test_loop_03()
+
+verify()

src/libasr/codegen/asr_to_wasm.cpp

@@ -2032,6 +2032,7 @@ class ASRToWASMVisitor : public ASR::BaseVisitor<ASRToWASMVisitor> {
             m_code_section, m_al,
             nesting_level -
                 cur_loop_nesting_level);  // emit_branch and label the loop
+        wasm::emit_b8(m_code_section, m_al, 0x05);  // starting of else
         wasm::emit_expr_end(m_code_section, m_al);  // end if
 
         nesting_level--;

src/libasr/codegen/wasm_to_x86.cpp

@@ -32,7 +32,8 @@ class X86Visitor : public WASMDecoder<X86Visitor>,
    public:
     X86Assembler &m_a;
     uint32_t cur_func_idx;
-    std::vector<std::string> unique_id;
+    std::vector<std::string> if_unique_id;
+    std::vector<std::string> loop_unique_id;
     int32_t last_vis_i32_const, last_last_vis_i32_const;
     std::unordered_map<int32_t, std::string> loc_to_str;
 
@@ -129,23 +130,59 @@ class X86Visitor : public WASMDecoder<X86Visitor>,
 
     void visit_EmtpyBlockType() {}
 
+    void visit_Br(uint32_t label_index) {
+        // Branch is used to jump to the `loop.head` or `loop.end`.
+        if (if_unique_id.size() - loop_unique_id.size() == label_index - 1) {
+            // cycle/continue or loop.end
+            m_a.asm_jmp_label(".loop.head_" + loop_unique_id.back());
+        } else {
+            // exit/break
+            m_a.asm_jmp_label(".loop.end_" + loop_unique_id.back());
+        }
+    }
+
+    void visit_Loop() {
+        loop_unique_id.push_back(std::to_string(offset));
+        /*
+        The loop statement starts with `loop.head`. The `loop.body` and
+        `loop.branch` are enclosed within the `if.block`. If the condition
+        fails, the loop is exited through `else.block`.
+        .head
+            .If
+                # Statements
+                .Br
+            .Else
+            .endIf
+        .end
+        */
+        m_a.add_label(".loop.head_" + loop_unique_id.back());
+        {
+            decode_instructions();
+        }
+        // end
+        m_a.add_label(".loop.end_" + loop_unique_id.back());
+        loop_unique_id.pop_back();
+    }
+
     void visit_If() {
-        unique_id.push_back(std::to_string(offset));
+        if_unique_id.push_back(std::to_string(offset));
+        // `eax` contains the logical value (true = 1, false = 0)
+        // of the if condition
         m_a.asm_pop_r32(X86Reg::eax);
         m_a.asm_cmp_r32_imm8(LFortran::X86Reg::eax, 1);
-        m_a.asm_je_label(".then_" + unique_id.back());
-        m_a.asm_jmp_label(".else_" + unique_id.back());
-        m_a.add_label(".then_" + unique_id.back());
+        m_a.asm_je_label(".then_" + if_unique_id.back());
+        m_a.asm_jmp_label(".else_" + if_unique_id.back());
+        m_a.add_label(".then_" + if_unique_id.back());
         {
             decode_instructions();
         }
-        m_a.add_label(".endif_" + unique_id.back());
-        unique_id.pop_back();
+        m_a.add_label(".endif_" + if_unique_id.back());
+        if_unique_id.pop_back();
     }
 
     void visit_Else() {
-        m_a.asm_jmp_label(".endif_" + unique_id.back());
-        m_a.add_label(".else_" + unique_id.back());
+        m_a.asm_jmp_label(".endif_" + if_unique_id.back());
+        m_a.add_label(".else_" + if_unique_id.back());
     }
 
     void visit_LocalGet(uint32_t localidx) {
@@ -225,6 +262,7 @@ class X86Visitor : public WASMDecoder<X86Visitor>,
         std::string label = std::to_string(offset);
         m_a.asm_pop_r32(X86Reg::ebx);
         m_a.asm_pop_r32(X86Reg::eax);
+        // `eax` and `ebx` contain the left and right operands, respectively
         m_a.asm_cmp_r32_r32(X86Reg::eax, X86Reg::ebx);
         if (compare_op == "Eq") {
             m_a.asm_je_label(".compare_1" + label);
@@ -241,6 +279,8 @@ class X86Visitor : public WASMDecoder<X86Visitor>,
         } else {
             throw CodeGenError("Comparison operator not implemented");
         }
+        // if the `compare` condition in `true`, jump to compare_1
+        // and assign `1` else assign `0`
         m_a.asm_push_imm8(0);
         m_a.asm_jmp_label(".compare.end_" + label);
         m_a.add_label(".compare_1" + label);

tests/reference/wat-loop1-e0046d4.json

@@ -6,7 +6,7 @@
     "outfile": null,
     "outfile_hash": null,
     "stdout": "wat-loop1-e0046d4.stdout",
-    "stdout_hash": "72c18793b437f96f1f96c9f8fc8cc253601fb360929216a4de1cb2f1",
+    "stdout_hash": "f2518c3df21a94fba3afb27274ecfae56de7beaaaa8b54b4c1fd84fa",
     "stderr": null,
     "stderr_hash": null,
     "returncode": 0

tests/reference/wat-loop1-e0046d4.stdout

@@ -48,6 +48,7 @@
                 i32.sub
                 local.set 0
                 br 1
+            else
             end
         end
         local.get 2
@@ -83,6 +84,7 @@
                 i32.mul
                 local.set 3
                 br 1
+            else
             end
         end
         local.get 3
@@ -121,6 +123,7 @@
                 i32.sub
                 local.set 0
                 br 1
+            else
             end
         end
         local.get 2