duskos

commit 08e09ae899f75ca75e4fd0da59fddb1a1ddc336f
parent e8db2623c4f71c55abadfcfe69eaaef09b226201
Author: Virgil Dupras <hsoft@hardcoded.net>
Date:   Tue,  8 Nov 2022 12:10:40 -0500

cc: improve pointer arithmetics

Diffstat:
M
fs/cc/ast.fs
 | 
26
+++++++++++++++++---------
M
fs/tests/cc/cc.fs
 | 
1
+
M
fs/tests/cc/test.c
 | 
4
++++

3 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/fs/cc/ast.fs b/fs/cc/ast.fs
@@ -144,12 +144,16 @@ extends ASTNode struct[ Arrow
 ]struct
 
 struct+[ ASTNode
-  \ Multiply the value of "node" by a factor of "n"
-  : :*=n ( n self -- ) >r ( n )
-    Constant :new ( cnode )
-    2 ( * ) AST_BINARYOP Op :new dup r@ Node :replace ( cnode bnode )
+  : _ ( opid n self -- ) >r ( opid n )
+    Constant :new ( opid cnode )
+    swap AST_BINARYOP Op :new dup r@ Node :replace ( cnode bnode )
     r> over Node :add ( cnode bnode ) Node :add ;
 
+  \ Multiply the value of "node" by a factor of "n"
+  : :*=n ( n self -- ) 2 ( * ) rot> _ ;
+  \ Divide the value of "node" by a factor of "n"
+  : :/=n ( n self -- ) 3 ( / ) rot> _ ;
+
   : :type dup id case ( self )
     AST_IDENT of =
       Ident :finddecl ?dup _assert CType :type endof
@@ -167,6 +171,7 @@ struct+[ ASTNode
 
   \ Return the "pointer arithmetic size" of "node".
   : :*arisz ( self -- n ) :type *ariunitsz ;
+  : :ptr? :type type*lvl bool ;
 ]struct
 
 extends Op struct[ UnaryOp
@@ -189,11 +194,14 @@ extends Op struct[ BinaryOp
   \ multiply the "not a pointer" one by the pointer's "arithmetic size".
   : :*ari ( self -- )
     dup opid ptrbop? not if drop exit then
-    firstchild ?dup _assert dup nextsibling ?dup _assert ( n1 n2 )
-    2dup :*arisz swap :*arisz 2dup = if \ same *arisz, nothing to do
-      2drop 2drop else \ different *arisz, adjust
-      ( n1 n2 sz2 sz1 ) < if swap then ( node-to-adjust pointer-node )
-      :*arisz swap :*=n then ;
+    dup firstchild ?dup _assert dup nextsibling ?dup _assert ( self n1 n2 )
+    over :ptr? if \ n1 is a pointer
+      swap :*arisz over :ptr? if ( self n2 sz ) \ both are pointers
+        nip swap :/=n else ( self n2 sz ) \ only n1 is a pointer
+        swap :*=n drop then ( )
+    else ( self n1 n2 ) \ n1 is not a pointer
+      dup :ptr? if ( self n1 n2 ) \ only n2 is a pointer
+        :*arisz swap :*=n else 2drop then ( self ) drop then ;
 ]struct
 
 extends ASTNode struct[ StrLit
diff --git a/fs/tests/cc/cc.fs b/fs/tests/cc/cc.fs
@@ -31,6 +31,7 @@ ptrset 54 #eq
 exprparens 9 #eq
 cnoop ( no result! ) scnt 0 #eq
 42 ptrari 46 #eq
+42 50 ptrari2 2 #eq
 array 52 #eq
 global 1234 #eq
 globalinc 1236 #eq
diff --git a/fs/tests/cc/test.c b/fs/tests/cc/test.c
@@ -122,6 +122,10 @@ int* ptrari(int *x) {
     cnoop(); // this doesn't mess up PS
     return x + 1;
 }
+// subtracting two pointers yield a number divided by the type size.
+int ptrari2(int *lo, int *hi) {
+    return hi-lo;
+}
 int array() {
     int a[3] = {42, 12, 2};
     return *a + a[1] - *(a+2);