Add test

compiler/vm.nim

@@ -489,16 +489,20 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       decodeB(rkFloat)
       regs[ra].floatVal = regs[rb].floatVal
     of opcAsgnIntFromFloat32:
-      decodeB(rkFloat)
+      let rb = instr.regB
+      ensureKind(rkInt)
       regs[ra].intVal = cast[int32](float32(regs[rb].floatVal))
     of opcAsgnIntFromFloat64:
-      decodeB(rkFloat)
+      let rb = instr.regB
+      ensureKind(rkInt)
       regs[ra].intVal = cast[int64](regs[rb].floatVal)
     of opcAsgnFloat32FromInt:
-      decodeB(rkInt)
+      let rb = instr.regB
+      ensureKind(rkFloat)
       regs[ra].floatVal = cast[float32](int32(regs[rb].intVal))
     of opcAsgnFloat64FromInt:
-      decodeB(rkInt)
+      let rb = instr.regB
+      ensureKind(rkFloat)
       regs[ra].floatVal = cast[float64](int64(regs[rb].intVal))      
     of opcAsgnComplex:
       asgnComplex(regs[ra], regs[instr.regB])

compiler/vmgen.nim

@@ -811,8 +811,7 @@ proc genCastIntFloat(c: PCtx; n: PNode; dest: var TDest) =
     c.freeTemp(tmp3)
   elif src_size == dst_size and src.kind in allowedIntegers and
                            dst.kind in {tyFloat, tyFloat32, tyFloat64}:
-
+    let tmp = c.genx(n[1])
-    let tmp = c.getTemp(n.sons[1].typ)
     if dest < 0: dest = c.getTemp(n[0].typ)
     if dst.kind == tyFloat32:
       c.gABC(n, opcAsgnFloat32FromInt, dest, tmp)
@@ -822,14 +821,14 @@ proc genCastIntFloat(c: PCtx; n: PNode; dest: var TDest) =
 
   elif src_size == dst_size and src.kind in {tyFloat, tyFloat32, tyFloat64} and
                            dst.kind in allowedIntegers:         
-              
+    let tmp = c.genx(n[1])
-    let tmp = c.getTemp(n.sons[1].typ)
     if dest < 0: dest = c.getTemp(n[0].typ)
     if src.kind == tyFloat32:
       c.gABC(n, opcAsgnIntFromFloat32, dest, tmp)
     else:
       c.gABC(n, opcAsgnIntFromFloat64, dest, tmp)
     c.freeTemp(tmp)
+
   else:
     globalError(c.config, n.info, "VM is only allowed to 'cast' between integers and/or floats of same size")
 

tests/vm/tcastint.nim

@@ -113,8 +113,55 @@ proc test() =
     doAssert(not compiles(cast[uint32](I8)))
     doAssert(not compiles(cast[uint64](I8)))
 
+
+proc test_float_cast =
+
+  const
+    exp_bias = 1023'i64
+    exp_shift = 52
+    exp_mask = 0x7ff'i64 shl exp_shift
+    mantissa_mask = 0xfffffffffffff'i64
+
+  let f = 8.0
+  let fx = cast[int64](f)
+  let exponent = ((fx and exp_mask) shr exp_shift) - exp_bias
+  let mantissa = fx and mantissa_mask
+  doAssert(exponent == 3, $exponent)
+  doAssert(mantissa == 0, $mantissa)
+
+  # construct 2^N float, where N is integer
+  let x = -2'i64 
+  let xx = (x + exp_bias) shl exp_shift
+  let xf = cast[float](xx)
+  doAssert(xf == 0.25, $xf)
+
+proc test_float32_cast =
+
+  const
+    exp_bias = 127'i32
+    exp_shift = 23
+    exp_mask = 0x7f800000'i32
+    mantissa_mask = 0x007ffff'i32
+
+  let f = -0.5'f32
+  let fx = cast[int32](f)
+  let exponent = ((fx and exp_mask) shr exp_shift) - exp_bias
+  let mantissa = fx and mantissa_mask
+  doAssert(exponent == -1, $exponent)
+  doAssert(mantissa == 0, $mantissa)
+
+  # construct 2^N float32 where N is integer
+  let x = 4'i32  
+  let xx = (x + exp_bias) shl exp_shift
+  let xf = cast[float32](xx)
+  doAssert(xf == 16.0'f32, $xf)
+
 test()
+test_float_cast()
+test_float32_cast()
 static:
   test()
+  test_float_cast()
+  test_float32_cast()
 
 echo "OK"