================
@@ -124,10 +143,11 @@ _mm_cvtm64_si64(__m64 __m)
/// written to the upper 32 bits of the result.
/// \returns A 64-bit integer vector of [8 x i8] containing the converted
/// values.
-static __inline__ __m64 __DEFAULT_FN_ATTRS
+static __inline__ __m64 __DEFAULT_FN_ATTRS_SSE2
_mm_packs_pi16(__m64 __m1, __m64 __m2)
{
- return (__m64)__builtin_ia32_packsswb((__v4hi)__m1, (__v4hi)__m2);
+ return __extract2_32(__builtin_ia32_packsswb128((__v8hi)__anyext128(__m1),
----------------
jyknight wrote:
So, the current version assembles to:
```
0: 66 0f 63 c1 packsswb %xmm1, %xmm0
4: 66 0f 70 c0 e8 pshufd $0xe8, %xmm0, %xmm0 # xmm0
= xmm0[0,2,2,3]
9: c3 retq
```
You're suggesting to instead shuffle the inputs, like:
```
return __trunc64(__builtin_ia32_packsswb128(
__builtin_shufflevector(__m1, __m2, 0, 1), (__v8hi){}));
```
I agree, that's better. Saves 1 byte of code, and also less register pressure.
```
0: 66 0f 6c c1 punpcklqdq %xmm1, %xmm0 # xmm0
= xmm0[0],xmm1[0]
4: 66 0f 63 c0 packsswb %xmm0, %xmm0
8: c3 retq
```
Done -- eliminated all uses of `__extract2_32`.
https://github.com/llvm/llvm-project/pull/96540
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