[llvm-commits] [llvm] r62661 - in /llvm/trunk: lib/Target/X86/X86InstrInfo.td test/CodeGen/X86/xor_not.ll

[Evan Cheng]

Author: evancheng
Date: Tue Jan 20 20:09:05 2009
New Revision: 62661

URL: http://llvm.org/viewvc/llvm-project?rev=62661&view=rev
Log:
Favors generating "not" over "xor -1". For example.
unsigned test(unsigned a) {
  return ~a;
}
llvm used to generate:
movl    $4294967295, %eax
xorl    4(%esp), %eax

Now it generates:
movl      4(%esp), %eax
notl      %eax

It's 3 bytes shorter.

Modified:
    llvm/trunk/lib/Target/X86/X86InstrInfo.td
    llvm/trunk/test/CodeGen/X86/xor_not.ll

Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.td?rev=62661&r1=62660&r2=62661&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.td (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.td Tue Jan 20 20:09:05 2009
@@ -1235,12 +1235,15 @@
 }
 } // Defs = [EFLAGS]
 
+// Match xor -1 to not. Favors these over a move imm + xor to save code size.
+let AddedComplexity = 15 in {
 def NOT8r  : I<0xF6, MRM2r, (outs GR8 :$dst), (ins GR8 :$src), "not{b}\t$dst",
                [(set GR8:$dst, (not GR8:$src))]>;
 def NOT16r : I<0xF7, MRM2r, (outs GR16:$dst), (ins GR16:$src), "not{w}\t$dst",
                [(set GR16:$dst, (not GR16:$src))]>, OpSize;
 def NOT32r : I<0xF7, MRM2r, (outs GR32:$dst), (ins GR32:$src), "not{l}\t$dst",
                [(set GR32:$dst, (not GR32:$src))]>;
+}
 let isTwoAddress = 0 in {
   def NOT8m  : I<0xF6, MRM2m, (outs), (ins i8mem :$dst), "not{b}\t$dst",
                  [(store (not (loadi8 addr:$dst)), addr:$dst)]>;

Modified: llvm/trunk/test/CodeGen/X86/xor_not.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/xor_not.ll?rev=62661&r1=62660&r2=62661&view=diff

==============================================================================
--- llvm/trunk/test/CodeGen/X86/xor_not.ll (original)
+++ llvm/trunk/test/CodeGen/X86/xor_not.ll Tue Jan 20 20:09:05 2009
@@ -1,4 +1,4 @@
-; RUN: llvm-as < %s | llc -march=x86 | grep {not\[lwb\]} | count 3
+; RUN: llvm-as < %s | llc -march=x86 | grep {not\[lwb\]} | count 4
 ; RUN: llvm-as < %s | llc -march=x86-64 | grep {not\[lwb\]}  | count 4
 define i32 @test(i32 %a, i32 %b) nounwind  {
 entry: