diff options
Diffstat (limited to 'compiler/rustc_apfloat/src')
| -rw-r--r-- | compiler/rustc_apfloat/src/ieee.rs | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/compiler/rustc_apfloat/src/ieee.rs b/compiler/rustc_apfloat/src/ieee.rs index e3d941cad7a..aafd6dfb89a 100644 --- a/compiler/rustc_apfloat/src/ieee.rs +++ b/compiler/rustc_apfloat/src/ieee.rs @@ -1511,6 +1511,18 @@ impl<S: Semantics, T: Semantics> FloatConvert<IeeeFloat<T>> for IeeeFloat<S> { sig::set_bit(&mut r.sig, T::PRECISION - 1); } + // If we are truncating NaN, it is possible that we shifted out all of the + // set bits in a signalling NaN payload. But NaN must remain NaN, so some + // bit in the significand must be set (otherwise it is Inf). + // This can only happen with sNaN. Set the 1st bit after the quiet bit, + // so that we still have an sNaN. + if r.sig[0] == 0 { + assert!(shift < 0, "Should not lose NaN payload on extend"); + assert!(T::PRECISION >= 3, "Unexpectedly narrow significand"); + assert!(*loses_info, "Missing payload should have set lost info"); + sig::set_bit(&mut r.sig, T::PRECISION - 3); + } + // gcc forces the Quiet bit on, which means (float)(double)(float_sNan) // does not give you back the same bits. This is dubious, and we // don't currently do it. You're really supposed to get |