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authorChris Lattner <sabre@nondot.org>2008-05-13 18:48:54 +0000
committerChris Lattner <sabre@nondot.org>2008-05-13 18:48:54 +0000
commit7171c836a93024d523b457b5a98782fa7ad5c97b (patch)
tree1aa4ec3766ccb1a25c056d55c7225c383fc4dc38 /lib
parentc3dac5cbfe1f7ce35bc8129a4e0d5d58bfd130ea (diff)
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51060 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r--lib/Target/X86/README-SSE.txt24
1 files changed, 24 insertions, 0 deletions
diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt
index 5c681e0..5f114a8 100644
--- a/lib/Target/X86/README-SSE.txt
+++ b/lib/Target/X86/README-SSE.txt
@@ -764,4 +764,28 @@ madd:
//===---------------------------------------------------------------------===//
+Consider:
+#include <emmintrin.h>
+__m128 foo2 (float x) {
+ return _mm_set_ps (0, 0, x, 0);
+}
+
+In x86-32 mode, we generate this spiffy code:
+
+_foo2:
+ movss 4(%esp), %xmm0
+ pshufd $81, %xmm0, %xmm0
+ ret
+
+in x86-64 mode, we generate this code, which could be better:
+
+_foo2:
+ xorps %xmm1, %xmm1
+ movss %xmm0, %xmm1
+ pshufd $81, %xmm1, %xmm0
+ ret
+
+In sse4 mode, we could use insertps to make both better.
+
+//===---------------------------------------------------------------------===//