Author: lattner
Date: Sun Aug 19 21:14:33 2007
New Revision: 41178
URL: http://llvm.org/viewvc/llvm-project?rev=41178&view=rev
Log:
add a note
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=41178&r1=41177&r2=41178&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Sun Aug 19 21:14:33 2007
@@ -1116,3 +1116,21 @@
addps %xmm1, %xmm0
ret
+//===---------------------------------------------------------------------===//
+
+Leaf functions that require one 4-byte spill slot have a prolog like this:
+
+_foo:
+ pushl %esi
+ subl $4, %esp
+...
+and an epilog like this:
+ addl $4, %esp
+ popl %esi
+ ret
+
+It would be smaller, and potentially faster, to push eax on entry and to
+pop into a dummy register instead of using addl/subl of esp. Just don't pop
+into any return registers :)
+
+//===---------------------------------------------------------------------===//
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