[llvm] r325317 - [X86] Don't zero_extend cmov up to i64, stop at i32.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Thu Feb 15 22:52:43 2018
New Revision: 325317

URL: http://llvm.org/viewvc/llvm-project?rev=325317&view=rev
Log:
[X86] Don't zero_extend cmov up to i64, stop at i32.

Zero extend from i32 to i64 is free. So extend from i16 to i32, and then use a free zero extend to finish.

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
    llvm/trunk/test/CodeGen/X86/cmov-promotion.ll

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=325317&r1=325316&r2=325317&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu Feb 15 22:52:43 2018
@@ -36028,7 +36028,7 @@ static SDValue getDivRem8(SDNode *N, Sel
 //         promotion).
 static SDValue combineToExtendCMOV(SDNode *Extend, SelectionDAG &DAG) {
   SDValue CMovN = Extend->getOperand(0);
-  if (CMovN.getOpcode() != X86ISD::CMOV)
+  if (CMovN.getOpcode() != X86ISD::CMOV || !CMovN.hasOneUse())
     return SDValue();
 
   EVT TargetVT = Extend->getValueType(0);
@@ -36039,20 +36039,35 @@ static SDValue combineToExtendCMOV(SDNod
   SDValue CMovOp0 = CMovN.getOperand(0);
   SDValue CMovOp1 = CMovN.getOperand(1);
 
-  bool DoPromoteCMOV =
-      (VT == MVT::i16 && (TargetVT == MVT::i32 || TargetVT == MVT::i64)) &&
-      CMovN.hasOneUse() &&
-      (isa<ConstantSDNode>(CMovOp0.getNode()) &&
-       isa<ConstantSDNode>(CMovOp1.getNode()));
+  if (!isa<ConstantSDNode>(CMovOp0.getNode()) ||
+      !isa<ConstantSDNode>(CMovOp0.getNode()))
+    return SDValue();
+
+  // Only extend to i32 or i64.
+  if (TargetVT != MVT::i32 && TargetVT != MVT::i64)
+    return SDValue();
 
-  if (!DoPromoteCMOV)
+  // Only extend from i16.
+  if (VT != MVT::i16)
     return SDValue();
 
-  CMovOp0 = DAG.getNode(ExtendOpcode, DL, TargetVT, CMovOp0);
-  CMovOp1 = DAG.getNode(ExtendOpcode, DL, TargetVT, CMovOp1);
+  // If this a zero extend to i64, we should only extend to i32 and use a free
+  // zero extend to finish.
+  EVT ExtendVT = TargetVT;
+  if (TargetVT == MVT::i64 && ExtendOpcode == ISD::ZERO_EXTEND)
+    ExtendVT = MVT::i32;
+
+  CMovOp0 = DAG.getNode(ExtendOpcode, DL, ExtendVT, CMovOp0);
+  CMovOp1 = DAG.getNode(ExtendOpcode, DL, ExtendVT, CMovOp1);
+
+  SDValue Res = DAG.getNode(X86ISD::CMOV, DL, ExtendVT, CMovOp0, CMovOp1,
+                            CMovN.getOperand(2), CMovN.getOperand(3));
+
+  // Finish extending if needed.
+  if (ExtendVT != TargetVT)
+    Res = DAG.getNode(ISD::ZERO_EXTEND, DL, TargetVT, Res);
 
-  return DAG.getNode(X86ISD::CMOV, DL, TargetVT, CMovOp0, CMovOp1,
-                     CMovN.getOperand(2), CMovN.getOperand(3));
+  return Res;
 }
 
 // Convert (vXiY *ext(vXi1 bitcast(iX))) to extend_in_reg(broadcast(iX)).

Modified: llvm/trunk/test/CodeGen/X86/cmov-promotion.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/cmov-promotion.ll?rev=325317&r1=325316&r2=325317&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/cmov-promotion.ll (original)
+++ llvm/trunk/test/CodeGen/X86/cmov-promotion.ll Thu Feb 15 22:52:43 2018
@@ -115,7 +115,7 @@ define i64 @cmov_zpromotion_16_to_64(i1
 ; CMOV-NEXT:    testb $1, %dil
 ; CMOV-NEXT:    movl $12414, %ecx # imm = 0x307E
 ; CMOV-NEXT:    movl $65535, %eax # imm = 0xFFFF
-; CMOV-NEXT:    cmovneq %rcx, %rax
+; CMOV-NEXT:    cmovnel %ecx, %eax
 ; CMOV-NEXT:    retq
 ;
 ; NO_CMOV-LABEL: cmov_zpromotion_16_to_64: