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-rw-r--r--libguile/vm-i-scheme.c38
1 files changed, 30 insertions, 8 deletions
diff --git a/libguile/vm-i-scheme.c b/libguile/vm-i-scheme.c
index 69ea8a544..3e80a0ef5 100644
--- a/libguile/vm-i-scheme.c
+++ b/libguile/vm-i-scheme.c
@@ -209,6 +209,10 @@ VM_DEFINE_FUNCTION (149, ge, "ge?", 2)
* Numeric functions
*/
+/* The maximum/minimum tagged integers. */
+#define INUM_MAX (INTPTR_MAX - 1)
+#define INUM_MIN (INTPTR_MIN + scm_tc2_int)
+
#undef FUNC2
#define FUNC2(CFUNC,SFUNC) \
{ \
@@ -231,12 +235,21 @@ VM_DEFINE_FUNCTION (150, add, "add", 2)
VM_DEFINE_FUNCTION (151, add1, "add1", 1)
{
ARGS1 (x);
- if (SCM_I_INUMP (x))
+
+ /* Check for overflow. */
+ if (SCM_LIKELY ((scm_t_intptr) x < INUM_MAX))
{
- scm_t_int64 n = SCM_I_INUM (x) + 1;
- if (SCM_FIXABLE (n))
- RETURN (SCM_I_MAKINUM (n));
+ SCM result;
+
+ /* Add the integers without untagging. */
+ result = SCM_PACK ((scm_t_intptr) x
+ + (scm_t_intptr) SCM_I_MAKINUM (1)
+ - scm_tc2_int);
+
+ if (SCM_LIKELY (SCM_I_INUMP (result)))
+ RETURN (result);
}
+
SYNC_REGISTER ();
RETURN (scm_sum (x, SCM_I_MAKINUM (1)));
}
@@ -249,12 +262,21 @@ VM_DEFINE_FUNCTION (152, sub, "sub", 2)
VM_DEFINE_FUNCTION (153, sub1, "sub1", 1)
{
ARGS1 (x);
- if (SCM_I_INUMP (x))
+
+ /* Check for underflow. */
+ if (SCM_LIKELY ((scm_t_intptr) x > INUM_MIN))
{
- scm_t_int64 n = SCM_I_INUM (x) - 1;
- if (SCM_FIXABLE (n))
- RETURN (SCM_I_MAKINUM (n));
+ SCM result;
+
+ /* Substract the integers without untagging. */
+ result = SCM_PACK ((scm_t_intptr) x
+ - (scm_t_intptr) SCM_I_MAKINUM (1)
+ + scm_tc2_int);
+
+ if (SCM_LIKELY (SCM_I_INUMP (result)))
+ RETURN (result);
}
+
SYNC_REGISTER ();
RETURN (scm_difference (x, SCM_I_MAKINUM (1)));
}