[llvm-commits] [llvm] r41359 - /llvm/trunk/lib/Target/X86/README-SSE.txt

[Chris Lattner]

Author: lattner
Date: Fri Aug 24 10:17:59 2007
New Revision: 41359

URL: http://llvm.org/viewvc/llvm-project?rev=41359&view=rev
Log:
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Modified:
    llvm/trunk/lib/Target/X86/README-SSE.txt

Modified: llvm/trunk/lib/Target/X86/README-SSE.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README-SSE.txt?rev=41359&r1=41358&r2=41359&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README-SSE.txt (original)
+++ llvm/trunk/lib/Target/X86/README-SSE.txt Fri Aug 24 10:17:59 2007
@@ -630,3 +630,17 @@
         ret
 
 //===---------------------------------------------------------------------===//
+
+We should materialize vecetor constants like "all ones" and "signbit" with 
+code like:
+
+     cmpeqps xmm1, xmm1   ; xmm1 = all-ones
+
+and:
+     cmpeqps xmm1, xmm1   ; xmm1 = all-ones
+     psrlq   xmm1, 31     ; xmm1 = all 100000000000...
+
+instead of using a load from the constant pool.  The later is important for
+ABS/NEG/copysign etc.
+
+//===---------------------------------------------------------------------===//