[clang] [Headers][X86] Allow pmuludq/pmuldq to be used in constexpr (PR #153293)

[Phoebe Wang via cfe-commits]

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@@ -389,6 +389,7 @@ __m64 test_mm_mul_su32(__m64 a, __m64 b) {
   // CHECK: mul <2 x i64> %{{.*}}, %{{.*}}
   return _mm_mul_su32(a, b);
 }
+TEST_CONSTEXPR(match_m64(_mm_mul_su32((__m64)(__v4hi){+1, -2, +3, -4}, (__m64)(__v4hi){-10, +8, +6, -4}), 2533154533212150));
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phoebewang wrote:

Yeah, but here we initialize it with v4Ni16.

https://github.com/llvm/llvm-project/pull/153293