rep

Makefile

@@ -6,7 +6,7 @@ all: kas
 kpc:
 	@cd vm && make --no-print-directory verbose=no
 
-kas: kpc as/k-as.py as/regs.lst as/
+kas: kpc as/regs.lst as/k-as.py
 	@cp vm/in/instrs.lst as
 
 DOSK = $(shell find ka -name '*.k')

as/k-as.py

@@ -394,26 +394,25 @@ def parse_instr(line):
     # Word 2 (rep|cond|ft1|ft2)
     w2 = 0
 
-    if '.' in instr:
-        w2 |= get_cond_mask(instr.split('.', 1)[1], line)
-        instr = instr.split('.', 1)[0]
+    if len(instr) > 2 and '.' in instr:
+        instr, suf = instr.split('.', 1)
+        
+        if len(instr) == 0:
+            print("Missing instruction name before suffixes: {}".format(line))
 
-    else:
-        instr = instr
+        if len(suf) > 2 and suf[:3] == "rep":
+            if len(suf) > 3:
+                suf = suf[3:]
 
-    if instr == "rep":
-        if params == None:
-            print("Missing instruction after rep prefix: {}".format(line))
-            leave()
-            sys.exit(1)
+                if len(suf) > 0 and suf[0] == '.':
+                    suf = suf[1:]
+            else:
+                suf = ''
 
-        w2 |= 0x8000    # 16th bit
-
-        if len(params.split(' ', 1)) == 2:
-            instr, params = params.split(' ', 1)
-        else:
-            instr = params.split(' ', 1)[0]
-            params = None
+            w2 |= 0x8000 # REP
+        
+        if len(suf) > 0:
+            w2 |= get_cond_mask(suf, line)
 
     instr_name = instr
     instr_args = ''

ka/crt/str/strcmp.k

@@ -21,7 +21,7 @@ strncmp:
     mov.cxz rax, 0
     ret.cxz
 
-    rep.e cmpzsb ax0, ax1
+    cmpzsb.rep.e ax0, ax1
 
     mov rax, b[ax0]
     sub rax, b[ax1]

ka/crt/str/strcpy.k

@@ -15,7 +15,7 @@ strncpy:
     mov rcx, ax2
     ret.cxz
 
-    rep.nz movsb ax0, ax1
+    movsb.rep.nz ax0, ax1
 
     ret
 
@@ -29,7 +29,7 @@ strnzcpy:
     dec rcx
     jmp.cxz .1
 
-    rep.nz movsb ax0, ax1
+    movsb.rep.nz ax0, ax1
 
 .1:
     mov b[ax0], 0

ka/crt/str/strlen.k

@@ -6,7 +6,7 @@
 ;
 strnlen:
     mov rcx, ax1
-    rep.nz scasb ax0, 0
+    scasb.rep.nz ax0, 0
     
     mov rax, ax1
     sub rax, rcx

ka/crt/str/strrev.k

@@ -16,10 +16,9 @@ strrev:
 
     ; go to str's end, just before
     ; the null terminator
-.1:
-    test b[ax1+1], b[ax1+1]
-    inc.nz ax1
-    jmp.nz .1
+    mov rcx, STRLEN_MAX
+    scazsb.rep.nz ax1
+    dec ax1
 
 .2:
     ; copy, going backward though str
@@ -48,10 +47,9 @@ strrev2:
 
     ; go to str's end, just before
     ; the null terminator
-.1:
-    test b[ax1+1], b[ax1+1]
-    inc.nz ax1
-    jmp.nz .1
+    mov rcx, STRLEN_MAX
+    scazsb.rep.nz ax1
+    dec ax1
 
     ; increase ax0 while decreasing ax1, performing exchanges
 .2:

ka/main.k

@@ -5,7 +5,7 @@
 ; Main function
 ;
 main:
-    call showoff
+    call itoa_test
     ret
 
 showoff:
@@ -35,12 +35,11 @@ ramdev_test:
     ret
 
 stosb_test:
-    cld
     mov rcx, 11
     mov rax, 33
     mov rdi, .buf
     mov rsi, .buf
-    rep stosb
+    stosb.rep
 
     mov rbx, rdi
     sub rbx, rsi

vm/in/INSTRS

@@ -412,10 +412,43 @@ lodsb r r
 # When one parameter is given, %str = RDI and $val = $1
 # When two parameters are given, %str = $1 and $val = $2
 #
+# Note that SCASx moves in the string no matter whether the value
+# was found or not; therefore when the value *is* found, it will
+# be sizeof(x) bytes below the current value of %str
+#
 scasb
 scasb rim
 scasb r rim
 
+#
+# Scan string for null terminator (SCAZSx)
+#
+#       CMP([%str], 0)
+#
+#       IF (ZF == 0)
+#           IF (DF == 0) THEN
+#               %str = %str + sizeof(x)
+#           ELSE
+#               %str = %str - sizeof(x)
+#           FI
+#       FI
+#
+# Sets CF, OF, ZF and SF according to the result of the comparison
+#
+# When no parameters are given, %str = RDI and $val = RAX
+# When one parameter is given, %str = RDI and $val = $1
+# When two parameters are given, %str = $1 and $val = $2
+#
+# Unlike SCASx, this instruction does NOT move forward after
+# finding what it was looking for. The instruction:
+#       REP.NZ SCAZSx %str
+# serves as a much faster shorthand for
+#       REP.NZ SCASx %str
+#       DEC %str
+#
+scazsb
+scazsb r
+
 #
 # Compare bytes in strings (CMPSx)
 #
@@ -445,7 +478,7 @@ cmpsb r r
 # Behaves precisely like CMPSx, except in the following case:
 #   - If both [%str1] and [%str2] are zero, clears ZF (indicating NOT EQUAL)
 #
-# This prevents 'rep.e cmpsb' from looping infinitely when both strings
+# This prevents 'REP.Z CMPZSx' from looping infinitely when both strings
 # have the exact same content; this allows for short strcmp's
 #
 cmpzsb

vm/in/string.c

@@ -170,6 +170,49 @@ IMPL_END;
 
 //----------------------------------------------------------------------------//
 
+static void scazs_impl(ctx_t *ctx, acc_t *p1, uint len)
+{
+    ulong reg;
+
+    if (p1)
+        reg = p1->reg;
+    else
+        reg = RDI;
+
+    ulong x = readmem(ctx, R(reg), len);
+    COMPARE(x, 0);
+
+    if (!(flg&ZF)) {
+        STR_MOVE(reg, len);
+    }
+}
+
+IMPL_START_0(scazsb)
+{
+    scazs_impl(ctx, p1, 1);
+}
+IMPL_END;
+
+IMPL_START_0(scazsw)
+{
+    scazs_impl(ctx, p1, 2);
+}
+IMPL_END;
+
+IMPL_START_0(scazsl)
+{
+    scazs_impl(ctx, p1, 4);
+}
+IMPL_END;
+
+IMPL_START_0(scazsq)
+{
+    scazs_impl(ctx, p1, 8);
+}
+IMPL_END;
+
+//----------------------------------------------------------------------------//
+
 static void cmps_impl(ctx_t *ctx, acc_t *p1, acc_t *p2, uint len)
 {
     ulong reg1, reg2;