[llvm-commits] [llvm] r93372 - /llvm/trunk/lib/Target/X86/README.txt
Chris Lattner
sabre at nondot.org
Wed Jan 13 15:28:40 PST 2010
Author: lattner
Date: Wed Jan 13 17:28:40 2010
New Revision: 93372
URL: http://llvm.org/viewvc/llvm-project?rev=93372&view=rev
Log:
X86 if conversion + tail merging issues from PR6032.
Modified:
llvm/trunk/lib/Target/X86/README.txt
Modified: llvm/trunk/lib/Target/X86/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README.txt?rev=93372&r1=93371&r2=93372&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Wed Jan 13 17:28:40 2010
@@ -1868,3 +1868,23 @@
information to add the "lock" prefix.
//===---------------------------------------------------------------------===//
+
+The X86 backend should be able to if-convert SSE comparisons like "ucomisd" to
+"cmpsd". For example, this code:
+
+double d1(double x) { return x == x ? x : x + x; }
+
+Compiles into:
+
+_d1:
+ ucomisd %xmm0, %xmm0
+ jnp LBB1_2
+ addsd %xmm0, %xmm0
+ ret
+LBB1_2:
+ ret
+
+Also, the 'ret's should be shared. This is PR6032.
+
+//===---------------------------------------------------------------------===//
+
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