[clang] [Headers][X86] Add rounding and exception notes to conversions (PR #83447)

[Paul T Robinson via cfe-commits]

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@@ -1405,11 +1413,12 @@ static __inline__ __m128d __DEFAULT_FN_ATTRS _mm_cvtss_sd(__m128d __a,
 
 /// Converts the two double-precision floating-point elements of a
 ///    128-bit vector of [2 x double] into two signed 32-bit integer values,
-///    returned in the lower 64 bits of a 128-bit vector of [4 x i32].
+///    returned in the lower 64 bits of a 128-bit vector of [4 x i32],
+///    truncating inexact results.
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pogo59 wrote:

Truncation is what distinguishes this from `_mm_cvtpd_epi32` so I think it is necessary? That information used to be in the second paragraph, I shortened it and moved it up to the first paragraph, to make that difference more obvious.
Behavior on overflow was added to the second paragraph.

Do you have a different suggestion for how to organize this information?

https://github.com/llvm/llvm-project/pull/83447