Author: lattner
Date: Tue Oct 2 22:40:24 2007
New Revision: 42564
URL: http://llvm.org/viewvc/llvm-project?rev=42564&view=rev
Log:
Bill's example is still not enough to repro this, but it has other issues that
seem significant as well.
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=42564&r1=42563&r2=42564&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Tue Oct 2 22:40:24 2007
@@ -1277,6 +1277,14 @@
movl %eax, -96(%ebp)
movw $0, -98(%ebp)
+This appears to be bad because the RA is not folding the store to the stack
+slot into the movl. The above instructions could be:
+ movl $32, -80(%ebp)
+...
+ movl $32, -84(%ebp)
+...
+This seems like a cross between remat and spill folding.
+
This has redundant subtractions of %eax from a stack slot. However, %ecx
doesn't
change, so we could simply subtract %eax from %ecx first and then use %ecx (or
vice-versa).
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