Add floating-point conditionalization so that the microcode will run

on machines with and without floating-point instructions.

The test depends on the host OS correctly setting the processor's CR0
(status word) bits.

diff --git a/v7/src/microcode/cmpauxmd/i386.m4 b/v7/src/microcode/cmpauxmd/i386.m4
index a1ec91ebecdd7bc5186559567cf8a3d6b5ab1099..61cb3af063afe0bd6aaf644e14847567cccb8583 100644 (file)
--- a/v7/src/microcode/cmpauxmd/i386.m4
+++ b/v7/src/microcode/cmpauxmd/i386.m4
@@ -1,6 +1,6 @@
 ### -*-Midas-*-
 ###
-###    $Header: /Users/cph/tmp/foo/mit-scheme/mit-scheme/v7/src/microcode/cmpauxmd/i386.m4,v 1.22 1992/03/30 21:10:50 jinx Exp $
+###    $Header: /Users/cph/tmp/foo/mit-scheme/mit-scheme/v7/src/microcode/cmpauxmd/i386.m4,v 1.23 1992/04/14 18:41:28 jinx Exp $
 ###
 ###    Copyright (c) 1992 Massachusetts Institute of Technology
 ###
@@ -292,6 +292,9 @@ allocate_longword(C_Stack_Pointer)
 define_data(C_Frame_Pointer)
 allocate_longword(C_Frame_Pointer)
 
+define_data(i387_presence)
+allocate_longword(i387_presence)
+
 define_data(Regstart)
 allocate_space(Regstart,128)
 define_data(Registers)
@@ -300,17 +303,33 @@ allocate_space(Registers,eval(REGBLOCK_SIZE_IN_OBJECTS*4))
 DECLARE_CODE_SEGMENT()
 declare_alignment(2)
 
-define_c_label(interface_initialize)
+define_c_label(i386_interface_initialize)
        OP(push,l)      REG(ebp)
        OP(mov,l)       TW(REG(esp),REG(ebp))
-IF387(`        OP(sub,l)       TW(IMM(4),REG(esp))
-       fstcw   WOF(-2,REG(ebp))
+       OP(xor,l)       TW(REG(eax),REG(eax))           # No 387 available
+
+# Unfortunately, the `movl cr0,ecx' instruction is privileged.
+# Use the deprecated `smsw cx' instruction instead.
+
+IF387(`        
+#      OP(mov,l)       TW(REG(cr0),REG(ecx))           # Test for 387 presence
+       smsw            REG(cx)
+       OP(mov,l)       TW(IMM(HEX(12)),REG(edx))
+       OP(and,l)       TW(REG(edx),REG(ecx))
+       OP(cmp,l)       TW(REG(edx),REG(ecx))
+       jne     i386_initialize_no_fp
+       OP(inc,l)       REG(eax)                        # 387 available
+       OP(sub,l)       TW(IMM(4),REG(esp))
+       fclex
+       fnstcw  WOF(-2,REG(ebp))
        # Set rounding mode to round-to-even, precision control to double,
        # mask the inexact result exception, and unmask the other exceptions.
-       OP(and,l)       TW(IMM(HEX(0000f0e0)),LOF(-4,REG(ebp)))
-       OP(or,l)        TW(IMM(HEX(00000220)),LOF(-4,REG(ebp)))
-       fldcw   WOF(-2,REG(ebp))')
-       OP(mov,w)       TW(REG(cs),REG(ax))             # Obtain code segment
+       OP(and,w)       TW(IMM(HEX(f0e0)),WOF(-2,REG(ebp)))
+       OP(or,w)        TW(IMM(HEX(0220)),WOF(-2,REG(ebp)))
+       fldcw   WOF(-2,REG(ebp))
+
+i386_initialize_no_fp:')
+       OP(mov,l)       TW(REG(eax),EDR(i387_presence))
        leave
        ret
 
@@ -331,7 +350,6 @@ ifdef(`DOS',
        OP(mov,l)       TW(REG(eax),EDR(C_Stack_Segment))
                                                        # and preserve it
 ')
-#      OP(mov,l)       TW(IMM(EDR(Registers)),regs)
        OP(lea,l)       TW(ABS(EDR(Registers)),regs)
        jmp     external_code_reference(interface_to_scheme)
 
@@ -345,7 +363,7 @@ define_debugging_label(scheme_to_interface_call)
        OP(pop,l)       REG(ecx)                        # arg1 = ret. add
        OP(add,l)       TW(IMM(4),REG(ecx))             # Skip format info
 #      jmp     scheme_to_interface
-
+\f
 define_c_label(asm_scheme_to_interface)
 define_debugging_label(scheme_to_interface)
        OP(mov,l)       TW(REG(esp),EDR(Ext_Stack_Pointer))
@@ -390,13 +408,18 @@ ifdef(`DOS',
        jmp     IJMP(REG(edx))
 
 define_c_label(interface_to_C)
-IF387(`        ffree   ST(0)                                   # Free floating "regs"
+IF387(`
+       OP(cmp,l)       TW(IMM(0),EDR(i387_presence))
+       je      interface_to_C_proceed
+       ffree   ST(0)                                   # Free floating "regs"
        ffree   ST(1)
        ffree   ST(2)
        ffree   ST(3)
        ffree   ST(4)
        ffree   ST(5)
-       ffree   ST(6)')
+       ffree   ST(6)
+interface_to_C_proceed:')
+
        OP(mov,l)       TW(REG(edx),REG(eax))           # Set up result
        OP(pop,l)       REG(ebx)                        # Restore callee-saves
        OP(pop,l)       REG(esi)                        #  registers
@@ -831,4 +854,20 @@ define_jump_indirection(generic_quotient,37)
 define_jump_indirection(generic_remainder,38)
 define_jump_indirection(generic_modulo,39)
 
+define_jump_indirection(nofp_decrement,22)
+define_jump_indirection(nofp_divide,23)
+define_jump_indirection(nofp_equal,24)
+define_jump_indirection(nofp_greater,25)
+define_jump_indirection(nofp_increment,26)
+define_jump_indirection(nofp_less,27)
+define_jump_indirection(nofp_subtract,28)
+define_jump_indirection(nofp_multiply,29)
+define_jump_indirection(nofp_negative,2a)
+define_jump_indirection(nofp_add,2b)
+define_jump_indirection(nofp_positive,2c)
+define_jump_indirection(nofp_zero,2d)
+define_jump_indirection(nofp_quotient,37)
+define_jump_indirection(nofp_remainder,38)
+define_jump_indirection(nofp_modulo,39)
+
 ifdef(`DOS',`end')