duskos

commit 4f34b25848b88e984439686565192e97a2df27f6
parent 98d5bc808b5d06458d18877a613559cc0fac84fc
Author: Virgil Dupras <hsoft@hardcoded.net>
Date:   Sun,  3 Jul 2022 15:57:12 -0400

asm: add the ability to call/jmp to a modrm

Diffstat:
M
fs/asm.fs
 | 
12
++++++++++--
M
fs/cc/vm.fs
 | 
2
+-
M
fs/tests/asm.fs
 | 
18
++++++++++++++----

3 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/fs/asm.fs b/fs/asm.fs
@@ -82,9 +82,17 @@
 : op ( opcode -- ) doer c, does> ( a -- ) c@ inh, ;
 $c3 op ret,
 
-\ Relative jumps
+\ Conditional jumps
 : op ( opcode -- ) doer , does> ( rel32 a -- ) @ op, , ;
-$00e9 op jmp,      $0f84 op jz,        $0f85 op jnz,
+$0f84 op jz,        $0f85 op jnz,
+
+\ JMP and CALL
+\ These are special. They can either be called with a modrm tgt, or with *no
+\ argument at all*. In the latter case, an absolute addr to call is waiting on
+\ PS.
+: op ( opcode -- ) doer c, c, does> ( rel32? a -- )
+  prefix, tgt 0< if 1+ c@ op, here - 4 - , else c@ $ff ( reg op ) modrm1, then ;
+$e9 4 op jmp,        $e8 2 op call,
 
 \ Single operand
 : op ( reg opcode -- ) doer , c, does> ( a -- )
diff --git a/fs/cc/vm.fs b/fs/cc/vm.fs
@@ -208,7 +208,7 @@ operands value 'curop
 \ TODO: call function with no return value.
 : vmcall>op1, ( -- )
   VM_*CONSTANT optype = _assert
-  oparg execute, VM_NONE optype!
+  oparg call, VM_NONE optype!
   selop1 noop#
   VM_REGISTER optype! regallot dup oparg! r! [ebp] mov,
   ebp 4 i32 add, 0 to callsz ;
diff --git a/fs/tests/asm.fs b/fs/tests/asm.fs
@@ -2,20 +2,30 @@
 ?f<< asm.fs
 testbegin
 \ Tests for asm.fs
-code foo
+code foo1
   eax 42 i32 mov,
   ebp 4 i32 sub,
   [ebp] eax mov,
   ret,
 
-foo 42 #eq
+foo1 42 #eq
 
 here 1234 , ( a )
-code foo
+code foo2
   ebx [i32] mov,
   ebp 4 i32 sub,
   [ebp] ebx mov,
   ret,
 
-foo 1234 #eq
+foo2 1234 #eq
+
+\ test call in its different forms
+code foo3
+  ' foo1 call,
+  eax ' foo1 i32 mov,
+  eax call,
+  ret,
+
+foo3 42 #eq 42 #eq
+
 testend