a note

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34670 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt
index bab5373d6521a69a337849e85a328daa0379472d..2b7f9ae4392e362e37d3ff2e8e22ceed8204006c 100644 (file)
--- a/lib/Target/X86/README-SSE.txt
+++ b/lib/Target/X86/README-SSE.txt
@@ -530,3 +530,45 @@ to loads from constant pool.
 Floating point max / min are commutable when -enable-unsafe-fp-path is
 specified. We should turn int_x86_sse_max_ss and X86ISD::FMIN etc. into other
 nodes which are selected to max / min instructions that are marked commutable.
+
+//===---------------------------------------------------------------------===//
+
+We should compile this:
+#include <xmmintrin.h>
+typedef union {
+  int i[4];
+  float f[4];
+  __m128 v;
+} vector4_t;
+void swizzle (const void *a, vector4_t * b, vector4_t * c) {
+  b->v = _mm_loadl_pi (b->v, (__m64 *) a);
+  c->v = _mm_loadl_pi (c->v, ((__m64 *) a) + 1);
+}
+
+to:
+
+_swizzle:
+        movl    4(%esp), %eax
+        movl    8(%esp), %edx
+        movl    12(%esp), %ecx
+        movlps  (%eax), %xmm0
+        movlps  %xmm0, (%edx)
+        movlps  8(%eax), %xmm0
+        movlps  %xmm0, (%ecx)
+        ret
+
+not:
+
+swizzle:
+        movl 8(%esp), %eax
+        movaps (%eax), %xmm0
+        movl 4(%esp), %ecx
+        movlps (%ecx), %xmm0
+        movaps %xmm0, (%eax)
+        movl 12(%esp), %eax
+        movaps (%eax), %xmm0
+        movlps 8(%ecx), %xmm0
+        movaps %xmm0, (%eax)
+        ret
+
+