icode: discard unused pure ICode expressions

Up to now, only unused IMove expressions where discarded.
So we also distinguish pure ICode from non pure ICode.

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

diff --git a/src/compiling/compiling_icode.nit b/src/compiling/compiling_icode.nit
index 847280b..97514ac 100644 (file)
--- a/src/compiling/compiling_icode.nit
+++ b/src/compiling/compiling_icode.nit
@@ -358,7 +358,9 @@ redef class ICode
                if r != null and r.slot_index != null then
                        assert s != null
                        v.add_assignment(v.register(r), s)
-               else if s != null and not self isa IMove then
+               else if s != null and not is_pure then
+                       # ICode with side effects must be evaluated
+                       # even if the result is not wanted
                        v.add_instr(s + ";")
                end
        end

diff --git a/src/icode/icode_base.nit b/src/icode/icode_base.nit
index f46ff5b..6a822e3 100644 (file)
--- a/src/icode/icode_base.nit
+++ b/src/icode/icode_base.nit
@@ -88,6 +88,9 @@ abstract class ICode
 
        # The location of the icode (if any)
        readable writable var _location: nullable Location = null
+
+       # Is the icode side effect free?
+       fun is_pure: Bool do return false
 end
 
 # An icode that uses no registers (no args)
@@ -274,6 +277,8 @@ special ICodeN
                super(e)
                _code = c
        end
+
+       redef readable writable var _is_pure: Bool = false
 end
 
 # A register assigment
@@ -286,6 +291,8 @@ special ICode1
                super(e)
                _result = r
        end
+
+       redef fun is_pure do return true
 end
 
 # An attribute read access
@@ -300,6 +307,8 @@ special ICode1
                super(r)
                _property = p
        end
+
+       redef fun is_pure do return true
 end
 
 # An attribute assignment
@@ -329,6 +338,8 @@ special ICode1
                super(r)
                _property = p
        end
+
+       redef fun is_pure do return true
 end
 
 # A type check
@@ -343,6 +354,8 @@ special ICode1
                super(e)
                _stype = t
        end
+
+       redef fun is_pure do return true
 end
 
 # The 'is' operator
@@ -353,6 +366,8 @@ special ICode2
        do
                super
        end
+
+       redef fun is_pure do return true
 end
 
 # The unary 'not' operation
@@ -363,6 +378,8 @@ special ICode1
        do
                super
        end
+
+       redef fun is_pure do return true
 end
 
 # Evaluate body once them return the same value again and again
@@ -383,6 +400,8 @@ special ICode0
        do
                _closure_decl = c
        end
+
+       redef fun is_pure do return true
 end
 
 #################################################

diff --git a/src/icode/icode_builder.nit b/src/icode/icode_builder.nit
index dbb26bd..88c3796 100644 (file)
--- a/src/icode/icode_builder.nit
+++ b/src/icode/icode_builder.nit
@@ -169,6 +169,7 @@ class ICodeBuilder
        fun lit_true_reg: IRegister
        do
                var e = new INative("TAG_Bool(true)", null)
+               e.is_pure = true
                return expr(e, module.type_bool)
        end
 
@@ -176,6 +177,7 @@ class ICodeBuilder
        fun lit_false_reg: IRegister
        do
                var e = new INative("TAG_Bool(false)", null)
+               e.is_pure = true
                return expr(e, module.type_bool)
        end
 

diff --git a/src/icode/icode_tools.nit b/src/icode/icode_tools.nit
index efdc0b7..5186233 100644 (file)
--- a/src/icode/icode_tools.nit
+++ b/src/icode/icode_tools.nit
@@ -258,7 +258,9 @@ end
 redef class INative
        redef fun inner_dup_with(d)
        do
-               return new INative(code, d.dup_iregs(exprs))
+               var c2 = new INative(code, d.dup_iregs(exprs))
+               c2.is_pure = is_pure
+               return c2
        end
 end