sepcomp: rewrote, fix and document `equal_test` in the c_primitive case

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/compiler/separate_compiler.nit b/src/compiler/separate_compiler.nit
index 532b844..00f3f00 100644 (file)
--- a/src/compiler/separate_compiler.nit
+++ b/src/compiler/separate_compiler.nit
@@ -1894,20 +1894,58 @@ class SeparateCompilerVisitor
                        value2 = tmp
                end
                if value1.mtype.is_c_primitive then
-                       if value2.mtype == value1.mtype then
+                       var t1 = value1.mtype
+                       assert t1 == value1.mcasttype
+
+                       # Fast case: same C type.
+                       if value2.mtype == t1 then
+                               # Same exact C primitive representation.
                                self.add("{res} = {value1} == {value2};")
-                       else if value2.mtype.is_c_primitive then
-                               self.add("{res} = 0; /* incompatible types {value1.mtype} vs. {value2.mtype}*/")
-                       else if value1.mtype.is_tagged then
-                               self.add("{res} = ({value2} != NULL) && ({self.autobox(value2, value1.mtype)} == {value1});")
+                               return res
+                       end
+
+                       # Complex case: value2 has a different representation
+                       # Thus, it should be checked if `value2` is type-compatible with `value1`
+                       # This compatibility is done statically if possible and dynamically else
+
+                       # Conjunction (ands) of dynamic tests according to the static knowledge
+                       var tests = new Array[String]
+
+                       var t2 = value2.mcasttype
+                       if t2 isa MNullableType then
+                               # The destination type cannot be null
+                               tests.add("({value2} != NULL)")
+                               t2 = t2.mtype
+                       else if t2 isa MNullType then
+                               # `value2` is known to be null, thus incompatible with a primitive
+                               self.add("{res} = 0; /* incompatible types {t1} vs. {t2}*/")
+                               return res
+                       end
+
+                       if t2 == t1 then
+                               # Same type but different representation.
+                       else if t2.is_c_primitive then
+                               # Type of `value2` is a different primitive type, thus incompatible
+                               self.add("{res} = 0; /* incompatible types {t1} vs. {t2}*/")
+                               return res
+                       else if t1.is_tagged then
+                               # To be equal, `value2` should also be correctly tagged
+                               tests.add("({extract_tag(value2)} == {t1.tag_value})")
                        else
-                               var mtype1 = value1.mtype.as(MClassType)
-                               self.require_declaration("class_{mtype1.c_name}")
-                               self.add("{res} = ({value2} != NULL) && ({value2}->class == &class_{mtype1.c_name});")
-                               self.add("if ({res}) \{")
-                               self.add("{res} = ({self.autobox(value2, value1.mtype)} == {value1});")
-                               self.add("\}")
+                               # To be equal, `value2` should also be boxed with the same class
+                               self.require_declaration("class_{t1.c_name}")
+                               tests.add "({class_info(value2)} == &class_{t1.c_name})"
+                       end
+
+                       # Compare the unboxed `value2` with `value1`
+                       if tests.not_empty then
+                               self.add "if ({tests.join(" && ")}) \{"
                        end
+                       self.add "{res} = {self.autobox(value2, t1)} == {value1};"
+                       if tests.not_empty then
+                               self.add "\} else {res} = 0;"
+                       end
+
                        return res
                end
                var maybe_null = true