[clang] [llvm] Clang: convert `__m64` intrinsics to unconditionally use SSE2 instead of MMX. (PR #96540)

[James Y Knight via cfe-commits]

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@@ -32,12 +32,13 @@ typedef unsigned int __v4su __attribute__((__vector_size__(16)));
 #endif
 
 /* Define the default attributes for the functions in this file. */
-#define __DEFAULT_FN_ATTRS                                                     \
-  __attribute__((__always_inline__, __nodebug__, __target__("sse,no-evex512"), \
-                 __min_vector_width__(128)))
-#define __DEFAULT_FN_ATTRS_MMX                                                 \
-  __attribute__((__always_inline__, __nodebug__,                               \
-                 __target__("mmx,sse,no-evex512"), __min_vector_width__(64)))
+#define __DEFAULT_FN_ATTRS __attribute__((__always_inline__, __nodebug__, __target__("sse,no-evex512"), __min_vector_width__(128)))
+#define __DEFAULT_FN_ATTRS_SSE2 __attribute__((__always_inline__, __nodebug__, __target__("sse2,no-evex512"), __min_vector_width__(64)))
+
+#define __trunc64(x) (__m64)__builtin_shufflevector((__v2di)(x), __extension__ (__v2di){}, 0)
+#define __zext128(x) (__m128i)__builtin_shufflevector((__v2si)(x), __extension__ (__v2si){}, 0, 1, 2, 3)
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jyknight wrote:

Vectors follow the same init-list rules as array/aggregate, where unmentioned elements are zeroed.

https://github.com/llvm/llvm-project/pull/96540