[llvm-commits] [llvm] r155853 - in /llvm/trunk: lib/Target/X86/X86ISelLowering.cpp test/CodeGen/X86/select.ll

[Manman Ren]

Author: mren
Date: Mon Apr 30 17:51:25 2012
New Revision: 155853

URL: http://llvm.org/viewvc/llvm-project?rev=155853&view=rev
Log:
X86: optimization for -(x != 0)

This patch will optimize -(x != 0) on X86
FROM 
cmpl	$0x01,%edi
sbbl	%eax,%eax
notl	%eax
TO
negl %edi
sbbl %eax %eax

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
    llvm/trunk/test/CodeGen/X86/select.ll

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=155853&r1=155852&r2=155853&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Mon Apr 30 17:51:25 2012
@@ -8589,6 +8589,22 @@
       SDValue Y = isAllOnes(Op2) ? Op1 : Op2;
 
       SDValue CmpOp0 = Cmp.getOperand(0);
+      // further optimization for special cases
+      // (select (x != 0), -1, 0) -> neg & sbb
+      // (select (x == 0), 0, -1) -> neg & sbb
+      if (ConstantSDNode *YC = dyn_cast<ConstantSDNode>(Y))
+        if (YC->isNullValue() && 
+            (isAllOnes(Op1) == (CondCode == X86::COND_NE))) {
+          SDVTList VTs = DAG.getVTList(CmpOp0.getValueType(), MVT::i32);
+          SDValue Neg = DAG.getNode(ISD::SUB, DL, VTs, 
+                                    DAG.getConstant(0, CmpOp0.getValueType()), 
+                                    CmpOp0);
+          SDValue Res = DAG.getNode(X86ISD::SETCC_CARRY, DL, Op.getValueType(),
+                                    DAG.getConstant(X86::COND_B, MVT::i8),
+                                    SDValue(Neg.getNode(), 1));
+          return Res;
+        }
+
       Cmp = DAG.getNode(X86ISD::CMP, DL, MVT::i32,
                         CmpOp0, DAG.getConstant(1, CmpOp0.getValueType()));
       Cmp = ConvertCmpIfNecessary(Cmp, DAG);

Modified: llvm/trunk/test/CodeGen/X86/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/select.ll?rev=155853&r1=155852&r2=155853&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/select.ll (original)
+++ llvm/trunk/test/CodeGen/X86/select.ll Mon Apr 30 17:51:25 2012
@@ -218,3 +218,24 @@
 ; CHECK-NEXT: ret
 }
 
+; rdar://10961709
+define i32 @test15(i32 %x) nounwind {
+entry:
+  %cmp = icmp ne i32 %x, 0
+  %sub = sext i1 %cmp to i32
+  ret i32 %sub
+; CHECK: test15:
+; CHECK: negl
+; CHECK: sbbl
+}
+
+define i32 @test16(i32 %x) nounwind {
+entry:
+  %c = icmp eq i32 %x, 0
+  %d = select i1 %c, i32 0, i32 -1
+  ret i32 %d
+; CHECK: test16:
+; CHECK: negl
+; CHECK: sbbl
+}
+