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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62661 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 73aa15a81d79fa951aec2cf217c0649a22670574..fbe03299e07a8ab4ddf3e4afef9d3acf2df7c40a 100644 (file)
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -1235,12 +1235,15 @@ let isTwoAddress = 0 in {
 }
 } // 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)]>;

diff --git a/test/CodeGen/X86/xor_not.ll b/test/CodeGen/X86/xor_not.ll
index 1e89ca8e0530e183dcc5594808a18c373ef72922..0b1abdf4152a4e2248054eeda14ca809f682979d 100644 (file)
--- a/test/CodeGen/X86/xor_not.ll
+++ b/test/CodeGen/X86/xor_not.ll
@@ -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: