implement rsub

libsrc/c64/extra/fp754kernal.s

@@ -13,6 +13,7 @@
     .import ___cbmkernal_fnegeax
     .import ___cbmkernal_ftosaddeax
     .import ___cbmkernal_ftossubeax
+    .import ___cbmkernal_ftosrsubeax
     .import ___cbmkernal_ftosdiveax
     .import ___cbmkernal_ftosmuleax
     .import ___cbmkernal_ftoseqeax
@@ -34,6 +35,7 @@
     .export fnegeax     := ___cbmkernal_fnegeax
     .export ftosaddeax  := ___cbmkernal_ftosaddeax
     .export ftossubeax  := ___cbmkernal_ftossubeax
+    .export ftosrsubeax  := ___cbmkernal_ftosrsubeax
     .export ftosdiveax  := ___cbmkernal_ftosdiveax
     .export ftosmuleax  := ___cbmkernal_ftosmuleax
     .export ftoseqeax   := ___cbmkernal_ftoseqeax

libsrc/float/cbmkernal/cbmfp-wrapper.s

@@ -224,6 +224,12 @@ ___cbmkernal_ftosdiveax:
 ___cbmkernal_ftosmuleax:
     jmp     __fmul
 
+    .import __frsub
+; Primary = Primary - TOS
+    .export ___cbmkernal_ftosrsubeax
+___cbmkernal_ftosrsubeax:
+    jmp     __frsub
+
 ;--------------------------------------------------------------
 
     .import __fcmp

libsrc/float/cbmkernal/cbmfp.s

@@ -659,6 +659,15 @@ __float_ret2:
         jmp __float_ret2
 .endmacro
 
+.macro __ffunc2c addr
+        jsr ___float_float_to_fac_arg
+        jsr __float_swap_fac_arg
+        __enable_basic_if_needed
+        lda FAC_EXPONENT
+        jsr addr
+        jmp __float_ret2
+.endmacro
+
         .export __fadd, __fsub, __fmul, __fdiv, __fpow
 
 ; float __fastcall__ _fadd(float f, float a);
@@ -674,6 +683,9 @@ __fpow:   __ffunc2a BASIC_ARG_FAC_Pow
 __fand:   __ffunc2b BASIC_ARG_FAC_And
 __for:    __ffunc2b BASIC_ARG_FAC_Or
 
+        .export __frsub
+__frsub:  __ffunc2c BASIC_ARG_FAC_Sub
+
 __float_ret3:
         ;jsr __basicoff
 .if .defined(__C64__)

libsrc/float/softfloat/softfloat-wrapper.s

@@ -126,6 +126,12 @@ ftosdiveax:
     ; arg1:     (sp),y (y=0..3)
      jmp _float32_div
 
+    .import _float32_rsub
+    .export ftosrsubeax
+ftosrsubeax:
+    ; arg0:     a/x/sreg/sreg+1
+    ; arg1:     (sp),y (y=0..3)
+     jmp _float32_rsub
 
      .import _float32_eq
      .import _float32_le

libsrc/float/softfloat/softfloat.c

@@ -899,6 +899,25 @@ float32 __fastcall__ float32_sub( float32 a, float32 b ) // original
 #endif
 }
 
+float32 __fastcall__ float32_rsub( float32 b, float32 a ) // swapped
+{
+#if 1
+    flag aSign, bSign;
+
+    aSign = extractFloat32Sign( a );
+    bSign = extractFloat32Sign( b );
+    if ( aSign == bSign ) {
+        return subFloat32Sigs( a, b, aSign );
+    }
+    else {
+        return addFloat32Sigs( a, b, aSign );
+    }
+#else
+    b = b;
+    return a;
+#endif
+}
+
 /*----------------------------------------------------------------------------
 | Returns the result of multiplying the single-precision floating-point values
 | `a' and `b'.  The operation is performed according to the IEEE Standard for

libsrc/float/softfloat/softfloat.h

@@ -91,6 +91,7 @@ float64 float32_to_float64( float32 );
 float32 __fastcall__ float32_round_to_int( float32 );
 float32 __fastcall__ float32_add( float32, float32 );
 float32 __fastcall__ float32_sub( float32, float32 );
+float32 __fastcall__ float32_rsub( float32, float32 );
 float32 __fastcall__ float32_mul( float32, float32 );
 float32 __fastcall__ float32_div( float32, float32 );
 float32 __fastcall__ float32_rem( float32, float32 );