emmintrin.h documentation fixes and updates

[dyung]

Summary

This is the result of several patches we made internally to update the documentation that we would like to have reviewed for possible submission.

The changes include:

1. Fixed innaccurate instruction mappings for various intrinsics.
2. Fixed description of NaN handling in comparison intrinsics.
3. Unify description of _mm_store_pd1 to match _mm_store1_pd.
4. Fix incorrect wording in various intrinsic descriptions. Previously the descriptions used "low-order" and "high-order" when the intended meaning was "even-indexed" and "odd-indexed".
5. Fix typos.
6. Add missing italics command (\a) for params and fixed some parameter spellings.

These patches were made by Craig Flores

[craig.topper]

LGTM

[kromanova]

cfe/trunk/lib/Headers/emmintrin.h

1143 ↗

(On Diff #128447)

Formatting is inconsistent with the rest of the changes above or below. One sentence here separated by the empty lines, where everywhere else it's 2 sentences.

4683 ↗

(On Diff #128447)

I'm not sure about this change.

Intel documentation says they generate MOVDQ2Q (don't have icc handy to try).
However, I've tried on Linux/X86_64 with clang and gcc, - and we just return.

[kromanova]

cfe/trunk/lib/Headers/emmintrin.h

3865 ↗

(On Diff #128447)

It's better if you use the same language as for many intrinsics "before" and "after". Just for consistency purpose.

/// This intrinsic is a utility function and does not correspond to a specific
///    instruction.

4683 ↗

(On Diff #128447)

Though I suspect it's possible to generate movdq2q, I couldn't come up with an test to trigger this instruction generation.
Should we revert this change?

__m64 fooepi64_pi64 (__m128i a, __m128 c)
{
  __m64 x;

  x = _mm_movepi64_pi64 (a);
  return x;
}

on Linux we generate return instruction.
I would expect (v)movq %xmm0,%rax to be generated instead of retq.
Am I missing something? Why do we return 64 bit integer in xmm register rather than in %rax?

4700 ↗

(On Diff #128447)

For Linux x86_64 I can only generate VMOVQ (or MOVQ) instructions respectively for AVX/non-AVX case.
Can we even generate MOVD+VMOVQ?
How we want to document this intrinsic?

I have a similar question as above.

__m128i foopi64_epi64 (__m64 a)
{
  __m128i x;

  x = _mm_movpi64_epi64 (a);
  return x;
}

Why we generate this code

        vmovq   %xmm0, %rax
        vmovq   %rax, %xmm0
        retq
}

instead of something simple like vmovq %rdi, %xmm0?

[efriedma]

cfe/trunk/lib/Headers/emmintrin.h

4683 ↗

(On Diff #128447)

The x86-64 calling convention rules say that __m64 is passed/returned in SSE registers.

Try the following, which generates movdq2q:

__m64 foo(__m128i a, __m128 c)
{
  return _mm_add_pi8(_mm_movepi64_pi64(a), _mm_set1_pi8(5));
}

[kromanova]

cfe/trunk/lib/Headers/emmintrin.h

4683 ↗

(On Diff #128447)

Thanks! That explains it :)
I can see that MOVDQ2Q gets generated.

What about intrinsic below, _mm_movpi64_epi64? Can we ever generate MOVD+VMOVQ as stated in the review?
Or should we write VMOVQ / MOVQ?

[efriedma]

cfe/trunk/lib/Headers/emmintrin.h

4683 ↗

(On Diff #128447)

Testcase:

#include <immintrin.h>
__m128 foo(__m128i a, __m128 c)
{
  return _mm_movpi64_epi64(_mm_add_pi8(_mm_movepi64_pi64(a), _mm_set1_pi8(5)));
}

In this case, we should generate movq2dq, but currently don't (I assume due to a missing DAGCombine). I don't see how you could ever get MOVD... but see https://reviews.llvm.org/rL321898, which could be the source of some confusion.

lib/Headers/emmintrin.h

 static __inline__ __m128d __DEFAULT_FN_ATTRS
 _mm_div_pd(__m128d __a, __m128d __b)
 {
   return (__m128d)((__v2df)__a / (__v2df)__b);
 }
 
 /// \brief Calculates the square root of the lower double-precision value of
 ///    the second operand and returns it in the lower 64 bits of the result.
-///    The upper 64 bits of the result are copied from the upper double-
-///    precision value of the first operand.
+///    The upper 64 bits of the result are copied from the upper
+///    double-precision value of the first operand.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VSQRTSD / SQRTSD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double] containing one of the operands. The
 ///    upper 64 bits of this operand are copied to the upper 64 bits of the

 static __inline__ __m128d __DEFAULT_FN_ATTRS
 _mm_sqrt_pd(__m128d __a)
 {
   return __builtin_ia32_sqrtpd((__v2df)__a);
 }
 
 /// \brief Compares lower 64-bit double-precision values of both operands, and
 ///    returns the lesser of the pair of values in the lower 64-bits of the
-///    result. The upper 64 bits of the result are copied from the upper double-
-///    precision value of the first operand.
+///    result. The upper 64 bits of the result are copied from the upper
+///    double-precision value of the first operand.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VMINSD / MINSD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double] containing one of the operands. The
 ///    lower 64 bits of this operand are used in the comparison.

 static __inline__ __m128d __DEFAULT_FN_ATTRS
 _mm_min_pd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_minpd((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares lower 64-bit double-precision values of both operands, and
 ///    returns the greater of the pair of values in the lower 64-bits of the
-///    result. The upper 64 bits of the result are copied from the upper double-
-///    precision value of the first operand.
+///    result. The upper 64 bits of the result are copied from the upper
+///    double-precision value of the first operand.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VMAXSD / MAXSD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double] containing one of the operands. The
 ///    lower 64 bits of this operand are used in the comparison.

 static __inline__ __m128d __DEFAULT_FN_ATTRS
 _mm_cmpnge_sd(__m128d __a, __m128d __b)
 {
   __m128d __c = __builtin_ia32_cmpnlesd((__v2df)__b, (__v2df)__a);
   return (__m128d) { __c[0], __a[1] };
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
-///    the two 128-bit floating-point vectors of [2 x double] for equality. The
-///    comparison yields 0 for false, 1 for true.
+///    the two 128-bit floating-point vectors of [2 x double] for equality.
+///
+///    The comparison yields 0 for false, 1 for true. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VCOMISD / COMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
-/// \returns An integer containing the comparison results.
+/// \returns An integer containing the comparison results. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_comieq_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_comisdeq((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is less than the corresponding value in
 ///    the second parameter.
 ///
-///    The comparison yields 0 for false, 1 for true.
+///    The comparison yields 0 for false, 1 for true. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VCOMISD / COMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
-/// \returns An integer containing the comparison results.
+/// \returns An integer containing the comparison results. If either of the two
+///     lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_comilt_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_comisdlt((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is less than or equal to the
 ///    corresponding value in the second parameter.
 ///
-///    The comparison yields 0 for false, 1 for true.
+///    The comparison yields 0 for false, 1 for true. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VCOMISD / COMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///     A 128-bit vector of [2 x double]. The lower double-precision value is
 ///     compared to the lower double-precision value of \a __a.
-/// \returns An integer containing the comparison results.
+/// \returns An integer containing the comparison results. If either of the two
+///     lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_comile_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_comisdle((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is greater than the corresponding value
 ///    in the second parameter.
 ///
-///    The comparison yields 0 for false, 1 for true.
+///    The comparison yields 0 for false, 1 for true. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VCOMISD / COMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
-/// \returns An integer containing the comparison results.
+/// \returns An integer containing the comparison results. If either of the two
+///     lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_comigt_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_comisdgt((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is greater than or equal to the
 ///    corresponding value in the second parameter.
 ///
-///    The comparison yields 0 for false, 1 for true.
+///    The comparison yields 0 for false, 1 for true. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VCOMISD / COMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
-/// \returns An integer containing the comparison results.
+/// \returns An integer containing the comparison results. If either of the two
+///    lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_comige_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_comisdge((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is unequal to the corresponding value in
 ///    the second parameter.
 ///
-///    The comparison yields 0 for false, 1 for true.
+///    The comparison yields 0 for false, 1 for true. If either of the two
+///    lower double-precision values is NaN, 1 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VCOMISD / COMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
-/// \returns An integer containing the comparison results.
+/// \returns An integer containing the comparison results. If either of the two
+///     lower double-precision values is NaN, 1 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_comineq_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_comisdneq((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] for equality. The
 ///    comparison yields 0 for false, 1 for true.
 ///
-///    If either of the two lower double-precision values is NaN, 1 is returned.
+///    If either of the two lower double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VUCOMISD / UCOMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
 /// \returns An integer containing the comparison results. If either of the two
-///    lower double-precision values is NaN, 1 is returned.
+///    lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_ucomieq_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_ucomisdeq((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is less than the corresponding value in
 ///    the second parameter.
 ///
 ///    The comparison yields 0 for false, 1 for true. If either of the two lower
-///    double-precision values is NaN, 1 is returned.
+///    double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VUCOMISD / UCOMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
 /// \returns An integer containing the comparison results. If either of the two
-///    lower double-precision values is NaN, 1 is returned.
+///    lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_ucomilt_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_ucomisdlt((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is less than or equal to the
 ///    corresponding value in the second parameter.
 ///
 ///    The comparison yields 0 for false, 1 for true. If either of the two lower
-///    double-precision values is NaN, 1 is returned.
+///    double-precision values is NaN, 0 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VUCOMISD / UCOMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///     A 128-bit vector of [2 x double]. The lower double-precision value is
 ///     compared to the lower double-precision value of \a __a.
 /// \returns An integer containing the comparison results. If either of the two
-///     lower double-precision values is NaN, 1 is returned.
+///     lower double-precision values is NaN, 0 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_ucomile_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_ucomisdle((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if

 }
 
 /// \brief Compares the lower double-precision floating-point values in each of
 ///    the two 128-bit floating-point vectors of [2 x double] to determine if
 ///    the value in the first parameter is unequal to the corresponding value in
 ///    the second parameter.
 ///
 ///    The comparison yields 0 for false, 1 for true. If either of the two lower
-///    double-precision values is NaN, 0 is returned.
+///    double-precision values is NaN, 1 is returned.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VUCOMISD / UCOMISD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __b.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. The lower double-precision value is
 ///    compared to the lower double-precision value of \a __a.
 /// \returns An integer containing the comparison result. If either of the two
-///    lower double-precision values is NaN, 0 is returned.
+///    lower double-precision values is NaN, 1 is returned.
 static __inline__ int __DEFAULT_FN_ATTRS
 _mm_ucomineq_sd(__m128d __a, __m128d __b)
 {
   return __builtin_ia32_ucomisdneq((__v2df)__a, (__v2df)__b);
 }
 
 /// \brief Converts the two double-precision floating-point elements of a
 ///    128-bit vector of [2 x double] into two single-precision floating-point
_mm_store_pd(double *__dp, __m128d __a)
   *(__m128d*)__dp = __a;
 }
 
 /// \brief Moves the lower 64 bits of a 128-bit vector of [2 x double] twice to
 ///    the upper and lower 64 bits of a memory location.
 ///
 /// \headerfile <x86intrin.h>
 ///
-/// This intrinsic corresponds to the <c>VMOVDDUP + VMOVAPD / MOVLHPS + MOVAPS </c> instruction.
+/// This intrinsic corresponds to the
+///   <c> VMOVDDUP + VMOVAPD / MOVLHPS + MOVAPS </c> instruction.
 ///
 /// \param __dp
 ///    A pointer to a memory location that can store two double-precision
 ///    values.
 /// \param __a
 ///    A 128-bit vector of [2 x double] whose lower 64 bits are copied to each
-///    of the values in \a dp.
+///    of the values in \a __dp.
 static __inline__ void __DEFAULT_FN_ATTRS
 _mm_store1_pd(double *__dp, __m128d __a)
 {
   __a = __builtin_shufflevector((__v2df)__a, (__v2df)__a, 0, 0);
   _mm_store_pd(__dp, __a);
 }
 
-/// \brief Stores a 128-bit vector of [2 x double] into an aligned memory
-///    location.
+/// \brief Moves the lower 64 bits of a 128-bit vector of [2 x double] twice to
+///    the upper and lower 64 bits of a memory location.
 ///
 /// \headerfile <x86intrin.h>
 ///
-/// This intrinsic corresponds to the <c> VMOVAPD / MOVAPD </c> instruction.
+/// This intrinsic corresponds to the
+///   <c> VMOVDDUP + VMOVAPD / MOVLHPS + MOVAPS </c> instruction.
 ///
 /// \param __dp
-///    A pointer to a 128-bit memory location. The address of the memory
-///    location has to be 16-byte aligned.
+///    A pointer to a memory location that can store two double-precision
+///    values.
 /// \param __a
-///    A 128-bit vector of [2 x double] containing the values to be stored.
+///    A 128-bit vector of [2 x double] whose lower 64 bits are copied to each
+///    of the values in \a __dp.
 static __inline__ void __DEFAULT_FN_ATTRS
 _mm_store_pd1(double *__dp, __m128d __a)
 {
   return _mm_store1_pd(__dp, __a);
 }
 
 /// \brief Stores a 128-bit vector of [2 x double] into an unaligned memory
 ///    location.
_mm_set1_epi8(char __b)
   return (__m128i)(__v16qi){ __b, __b, __b, __b, __b, __b, __b, __b, __b, __b, __b, __b, __b, __b, __b, __b };
 }
 
 /// \brief Constructs a 128-bit integer vector, initialized in reverse order
 ///     with the specified 64-bit integral values.
 ///
 /// \headerfile <x86intrin.h>
 ///
-/// This intrinsic corresponds to the <c> VPUNPCKLQDQ / PUNPCKLQDQ </c>
-///   instruction.
+/// This intrinsic does not correspond to a specific instruction.
 ///
 /// \param __q0
 ///    A 64-bit integral value used to initialize the lower 64 bits of the
 ///    result.
 /// \param __q1
 ///    A 64-bit integral value used to initialize the upper 64 bits of the
 ///    result.
 /// \returns An initialized 128-bit integer vector.
_mm_storeu_si128(__m128i *__p, __m128i __b)
   } __attribute__((__packed__, __may_alias__));
   ((struct __storeu_si128*)__p)->__v = __b;
 }
 
 /// \brief Moves bytes selected by the mask from the first operand to the
 ///    specified unaligned memory location. When a mask bit is 1, the
 ///    corresponding byte is written, otherwise it is not written.
 ///
-///    To minimize caching, the date is flagged as non-temporal (unlikely to be
+///    To minimize caching, the data is flagged as non-temporal (unlikely to be
 ///    used again soon). Exception and trap behavior for elements not selected
 ///    for storage to memory are implementation dependent.
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VMASKMOVDQU / MASKMOVDQU </c>
 ///   instruction.
 ///

 ///    Bits [127:96] are written to bits [127:96] of the destination.
 /// \returns A 128-bit vector of [4 x i32] containing the interleaved values.
 static __inline__ __m128i __DEFAULT_FN_ATTRS
 _mm_unpackhi_epi32(__m128i __a, __m128i __b)
 {
   return (__m128i)__builtin_shufflevector((__v4si)__a, (__v4si)__b, 2, 4+2, 3, 4+3);
 }
 
-/// \brief Unpacks the high-order (odd-indexed) values from two 128-bit vectors
-///    of [2 x i64] and interleaves them into a 128-bit vector of [2 x i64].
+/// \brief Unpacks the high-order 64-bit elements from two 128-bit vectors of
+///    [2 x i64] and interleaves them into a 128-bit vector of [2 x i64].
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VPUNPCKHQDQ / PUNPCKHQDQ </c>
 ///   instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x i64]. \n
_mm_unpacklo_epi64(__m128i __a, __m128i __b)
   return (__m128i)__builtin_shufflevector((__v2di)__a, (__v2di)__b, 0, 2+0);
 }
 
 /// \brief Returns the lower 64 bits of a 128-bit integer vector as a 64-bit
 ///    integer.
 ///
 /// \headerfile <x86intrin.h>
 ///
-/// This intrinsic has no corresponding instruction.
+/// This intrinsic corresponds to the <c> MOVDQ2Q </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit integer vector operand. The lower 64 bits are moved to the
 ///    destination.
 /// \returns A 64-bit integer containing the lower 64 bits of the parameter.
 static __inline__ __m64 __DEFAULT_FN_ATTRS
 _mm_movepi64_pi64(__m128i __a)
 {
   return (__m64)__a[0];
 }
 
 /// \brief Moves the 64-bit operand to a 128-bit integer vector, zeroing the
 ///    upper bits.
 ///
 /// \headerfile <x86intrin.h>
 ///
-/// This intrinsic corresponds to the <c> VMOVQ / MOVQ / MOVD </c> instruction.
+/// This intrinsic corresponds to the <c> MOVD+VMOVQ </c> instruction.
 ///
 /// \param __a
 ///    A 64-bit value.
 /// \returns A 128-bit integer vector. The lower 64 bits contain the value from
 ///    the operand. The upper 64 bits are assigned zeros.
 static __inline__ __m128i __DEFAULT_FN_ATTRS
 _mm_movpi64_epi64(__m64 __a)
 {

 /// \returns A 128-bit integer vector. The lower 64 bits contain the value from
 ///    the operand. The upper 64 bits are assigned zeros.
 static __inline__ __m128i __DEFAULT_FN_ATTRS
 _mm_move_epi64(__m128i __a)
 {
   return __builtin_shufflevector((__v2di)__a, (__m128i){ 0 }, 0, 2);
 }
 
-/// \brief Unpacks the high-order (odd-indexed) values from two 128-bit vectors
-///    of [2 x double] and interleaves them into a 128-bit vector of [2 x
+/// \brief Unpacks the high-order 64-bit elements from two 128-bit vectors of
+///    [2 x double] and interleaves them into a 128-bit vector of [2 x
 ///    double].
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VUNPCKHPD / UNPCKHPD </c> instruction.
 ///
 /// \param __a
 ///    A 128-bit vector of [2 x double]. \n
 ///    Bits [127:64] are written to bits [63:0] of the destination.
 /// \param __b
 ///    A 128-bit vector of [2 x double]. \n
 ///    Bits [127:64] are written to bits [127:64] of the destination.
 /// \returns A 128-bit vector of [2 x double] containing the interleaved values.
 static __inline__ __m128d __DEFAULT_FN_ATTRS
 _mm_unpackhi_pd(__m128d __a, __m128d __b)
 {
   return __builtin_shufflevector((__v2df)__a, (__v2df)__b, 1, 2+1);
 }
 
-/// \brief Unpacks the low-order (even-indexed) values from two 128-bit vectors
+/// \brief Unpacks the low-order 64-bit elements from two 128-bit vectors
 ///    of [2 x double] and interleaves them into a 128-bit vector of [2 x
 ///    double].
 ///
 /// \headerfile <x86intrin.h>
 ///
 /// This intrinsic corresponds to the <c> VUNPCKLPD / UNPCKLPD </c> instruction.
 ///
 /// \param __a

 /// This intrinsic corresponds to the <c> VSHUFPD / SHUFPD </c> instruction.
 ///
 /// \param a
 ///    A 128-bit vector of [2 x double].
 /// \param b
 ///    A 128-bit vector of [2 x double].
 /// \param i
 ///    An 8-bit immediate value. The least significant two bits specify which
-///    elements to copy from a and b: \n
-///    Bit[0] = 0: lower element of a copied to lower element of result. \n
-///    Bit[0] = 1: upper element of a copied to lower element of result. \n
+///    elements to copy from \a a and \a b: \n
+///    Bit[0] = 0: lower element of \a a copied to lower element of result. \n
+///    Bit[0] = 1: upper element of \a a copied to lower element of result. \n
 ///    Bit[1] = 0: lower element of \a b copied to upper element of result. \n
 ///    Bit[1] = 1: upper element of \a b copied to upper element of result. \n
 /// \returns A 128-bit vector of [2 x double] containing the shuffled values.
 #define _mm_shuffle_pd(a, b, i) __extension__ ({ \
   (__m128d)__builtin_shufflevector((__v2df)(__m128d)(a), (__v2df)(__m128d)(b), \
                                    0 + (((i) >> 0) & 0x1), \
                                    2 + (((i) >> 1) & 0x1)); })