New entry.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45280 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt
index aa3405ca33922cf2e99ccb734b675a6310130004..b4fc53ad0aac29c3c3fead2ce37f7655b5a8a530 100644 (file)
--- a/lib/Target/X86/README-SSE.txt
+++ b/lib/Target/X86/README-SSE.txt
@@ -741,3 +741,18 @@ save, as a really-signed value would be undefined for pslld.
 
 
 //===---------------------------------------------------------------------===//
+
+#include <math.h>
+int t1(double d) { return signbit(d); }
+
+This currently compiles to:
+       subl    $12, %esp
+       movsd   16(%esp), %xmm0
+       movsd   %xmm0, (%esp)
+       movl    4(%esp), %eax
+       shrl    $31, %eax
+       addl    $12, %esp
+       ret
+
+We should use movmskp{s|d} instead.
+