[llvm-commits] [llvm] r52663 - /llvm/trunk/lib/Target/X86/README.txt

Dan Gohman gohman at apple.com
Mon Jun 23 17:53:07 PDT 2008


Author: djg
Date: Mon Jun 23 19:53:07 2008
New Revision: 52663

URL: http://llvm.org/viewvc/llvm-project?rev=52663&view=rev
Log:
Add a note about a potential PIC optimization.

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=52663&r1=52662&r2=52663&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Mon Jun 23 19:53:07 2008
@@ -1709,3 +1709,10 @@
 it would be better to codegen as: x+~y  (notl+addl)
 
 //===---------------------------------------------------------------------===//
+
+We should consider using __i686.get_pc_thunk.bx for MOVPC32r (used for PIC)
+on targets that support it, such as Linux and similar targets, in place of
+the call-a-label trick. It's said to be friendlier to branch-prediction
+hardware because it pairs a ret with the call.
+
+//===---------------------------------------------------------------------===//





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