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Merge pull request #9496 from cooldome/vm_float_casts

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VM: add int <-> float casts of the same size
This commit is contained in:
Arne Döring
2018-10-28 11:56:30 +01:00
committed by GitHub
parent f2cd8ed99a 2f781781d0
commit 2fa13040b9
5 changed files with 94 additions and 5 deletions
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47
tests/vm/tcastint.nim
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@@ -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"