Improve XFIXNUM cleanup a bit

Based on Pip Cet’s review (Bug#36370#13).
* src/ccl.c (Fccl_execute_on_string): Use clearer indexing.
* src/dosfns.c (Fint86, Fdos_memput):
Avoid runtime checks for negative fixnums when debugging.
This restores the earlier machine code.
* src/lisp.h (XFIXNUM, XUFIXNUM): Use eassert, not eassume.
(XFIXNAT): At the start, merely eassert FIXNUMP rather
than eassuming FIXNATP.  At the end, eassume that the
result is nonnegative.  This restores help to the compiler
that the previous patch mistakenly removed.

3 files changed, 19 insertions, 17 deletions

diff --git a/src/ccl.c b/src/ccl.c
index f1d4c28df1c..ff42c6f25fc 100644
--- a/src/ccl.c
+++ b/src/ccl.c
@@ -2062,9 +2062,9 @@ usage: (ccl-execute-on-string CCL-PROGRAM STATUS STRING &optional CONTINUE UNIBY
       if (TYPE_RANGED_FIXNUMP (int, AREF (status, i)))
         ccl.reg[i] = XFIXNUM (AREF (status, i));
     }
-  if (FIXNUMP (AREF (status, i)))
+  if (FIXNUMP (AREF (status, 8)))
     {
-      EMACS_INT ic = XFIXNUM (AREF (status, i));
+      EMACS_INT ic = XFIXNUM (AREF (status, 8));
       if (ccl.ic < ic && ic < ccl.size)
         ccl.ic = ic;
     }
diff --git a/src/dosfns.c b/src/dosfns.c
index fb5bcc9ad3f..635f29bd656 100644
--- a/src/dosfns.c
+++ b/src/dosfns.c
@@ -72,16 +72,16 @@ REGISTERS should be a vector produced by `make-register' and
   if (no < 0 || no > 0xff || ASIZE (registers) != 8)
     return Qnil;
   for (i = 0; i < 8; i++)
-    CHECK_FIXNAT (AREF (registers, i));
+    CHECK_FIXNUM (AREF (registers, i));
 
-  inregs.x.ax    = (unsigned long) XFIXNAT (AREF (registers, 0));
-  inregs.x.bx    = (unsigned long) XFIXNAT (AREF (registers, 1));
-  inregs.x.cx    = (unsigned long) XFIXNAT (AREF (registers, 2));
-  inregs.x.dx    = (unsigned long) XFIXNAT (AREF (registers, 3));
-  inregs.x.si    = (unsigned long) XFIXNAT (AREF (registers, 4));
-  inregs.x.di    = (unsigned long) XFIXNAT (AREF (registers, 5));
-  inregs.x.cflag = (unsigned long) XFIXNAT (AREF (registers, 6));
-  inregs.x.flags = (unsigned long) XFIXNAT (AREF (registers, 7));
+  inregs.x.ax    = (unsigned long) XFIXNUM (AREF (registers, 0));
+  inregs.x.bx    = (unsigned long) XFIXNUM (AREF (registers, 1));
+  inregs.x.cx    = (unsigned long) XFIXNUM (AREF (registers, 2));
+  inregs.x.dx    = (unsigned long) XFIXNUM (AREF (registers, 3));
+  inregs.x.si    = (unsigned long) XFIXNUM (AREF (registers, 4));
+  inregs.x.di    = (unsigned long) XFIXNUM (AREF (registers, 5));
+  inregs.x.cflag = (unsigned long) XFIXNUM (AREF (registers, 6));
+  inregs.x.flags = (unsigned long) XFIXNUM (AREF (registers, 7));
 
   int86 (no, &inregs, &outregs);
 
@@ -139,8 +139,8 @@ DEFUN ("msdos-memput", Fdos_memput, Sdos_memput, 2, 2, 0,
 
   for (i = 0; i < len; i++)
     {
-      CHECK_FIXNAT (AREF (vector, i));
-      buf[i] = (unsigned char) XFIXNAT (AREF (vector, i)) & 0xFF;
+      CHECK_FIXNUM (AREF (vector, i));
+      buf[i] = (unsigned char) XFIXNUM (AREF (vector, i)) & 0xFF;
     }
 
   dosmemput (buf, len, offs);
diff --git a/src/lisp.h b/src/lisp.h
index 077d2360654..a0619e64f20 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1195,7 +1195,7 @@ INLINE bool
 INLINE EMACS_INT
 XFIXNUM (Lisp_Object a)
 {
-  eassume (FIXNUMP (a));
+  eassert (FIXNUMP (a));
   return XFIXNUM_RAW (a);
 }
 
@@ -1209,7 +1209,7 @@ XUFIXNUM_RAW (Lisp_Object a)
 INLINE EMACS_UINT
 XUFIXNUM (Lisp_Object a)
 {
-  eassume (FIXNUMP (a));
+  eassert (FIXNUMP (a));
   return XUFIXNUM_RAW (a);
 }
 
@@ -2828,9 +2828,11 @@ FIXNATP (Lisp_Object x)
 INLINE EMACS_INT
 XFIXNAT (Lisp_Object a)
 {
-  eassume (FIXNATP (a));
+  eassert (FIXNUMP (a));
   EMACS_INT int0 = Lisp_Int0;
-  return USE_LSB_TAG ? XFIXNUM (a) : XLI (a) - (int0 << VALBITS);
+  EMACS_INT result = USE_LSB_TAG ? XFIXNUM (a) : XLI (a) - (int0 << VALBITS);
+  eassume (0 <= result);
+  return result;
 }
 
 INLINE bool