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List:       llvm-commits
Subject:    [PATCH] D37317: [X86] Don't pull carry through X86ISD::ADD carryin, -1 if we can't guranteed we're r
From:       Phabricator via Phabricator via llvm-commits <llvm-commits () lists ! llvm ! org>
Date:       2017-08-31 21:40:49
Message-ID: db7f9080969ef58146f1386e378a15ce () localhost ! localdomain
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This revision was automatically updated to reflect the committed changes.
Closed by commit rL312285: [X86] Don't pull carry through X86ISD::ADD carryin, -1 if \
we can't guranteed… (authored by ctopper).

Changed prior to commit:
  https://reviews.llvm.org/D37317?vs=113449&id=113479#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D37317

Files:
  llvm/trunk/lib/Target/X86/X86ISelLowering.cpp


["D37317.113479.patch" (text/x-patch)]

Index: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
@@ -30939,11 +30939,40 @@
   return true;
 }
 
+// When legalizing carry, we create carries via add X, -1
+// If that comes from an actual carry, via setcc, we use the
+// carry directly.
+static SDValue combineCarryThroughADD(SDValue EFLAGS) {
+  if (EFLAGS.getOpcode() == X86ISD::ADD) {
+    if (isAllOnesConstant(EFLAGS.getOperand(1))) {
+      SDValue Carry = EFLAGS.getOperand(0);
+      while (Carry.getOpcode() == ISD::TRUNCATE ||
+             Carry.getOpcode() == ISD::ZERO_EXTEND ||
+             Carry.getOpcode() == ISD::SIGN_EXTEND ||
+             Carry.getOpcode() == ISD::ANY_EXTEND ||
+             (Carry.getOpcode() == ISD::AND &&
+              isOneConstant(Carry.getOperand(1))))
+        Carry = Carry.getOperand(0);
+      if (Carry.getOpcode() == X86ISD::SETCC ||
+          Carry.getOpcode() == X86ISD::SETCC_CARRY) {
+        if (Carry.getConstantOperandVal(0) == X86::COND_B)
+          return Carry.getOperand(1);
+      }
+    }
+  }
+
+  return SDValue();
+}
+
 /// Optimize an EFLAGS definition used according to the condition code \p CC
 /// into a simpler EFLAGS value, potentially returning a new \p CC and replacing
 /// uses of chain values.
 static SDValue combineSetCCEFLAGS(SDValue EFLAGS, X86::CondCode &CC,
                                   SelectionDAG &DAG) {
+  if (CC == X86::COND_B)
+    if (SDValue Flags = combineCarryThroughADD(EFLAGS))
+      return Flags;
+
   if (SDValue R = checkBoolTestSetCCCombine(EFLAGS, CC))
     return R;
   return combineSetCCAtomicArith(EFLAGS, CC, DAG);
@@ -34987,27 +35016,13 @@
   return SDValue();
 }
 
-// Optimize RES, EFLAGS = X86ISD::ADD LHS, RHS
-static SDValue combineX86ADD(SDNode *N, SelectionDAG &DAG,
-                             X86TargetLowering::DAGCombinerInfo &DCI) {
-  // When legalizing carry, we create carries via add X, -1
-  // If that comes from an actual carry, via setcc, we use the
-  // carry directly.
-  if (isAllOnesConstant(N->getOperand(1)) && N->hasAnyUseOfValue(1)) {
-    SDValue Carry = N->getOperand(0);
-    while (Carry.getOpcode() == ISD::TRUNCATE ||
-           Carry.getOpcode() == ISD::ZERO_EXTEND ||
-           Carry.getOpcode() == ISD::SIGN_EXTEND ||
-           Carry.getOpcode() == ISD::ANY_EXTEND ||
-           (Carry.getOpcode() == ISD::AND &&
-            isOneConstant(Carry.getOperand(1))))
-      Carry = Carry.getOperand(0);
-
-    if (Carry.getOpcode() == X86ISD::SETCC ||
-        Carry.getOpcode() == X86ISD::SETCC_CARRY) {
-      if (Carry.getConstantOperandVal(0) == X86::COND_B)
-        return DCI.CombineTo(N, SDValue(N, 0), Carry.getOperand(1));
-    }
+static SDValue combineSBB(SDNode *N, SelectionDAG &DAG) {
+  if (SDValue Flags = combineCarryThroughADD(N->getOperand(2))) {
+    MVT VT = N->getSimpleValueType(0);
+    SDVTList VTs = DAG.getVTList(VT, MVT::i32);
+    return DAG.getNode(X86ISD::SBB, SDLoc(N), VTs,
+                       N->getOperand(0), N->getOperand(1),
+                       Flags);
   }
 
   return SDValue();
@@ -35036,6 +35051,14 @@
     return DCI.CombineTo(N, Res1, CarryOut);
   }
 
+  if (SDValue Flags = combineCarryThroughADD(N->getOperand(2))) {
+    MVT VT = N->getSimpleValueType(0);
+    SDVTList VTs = DAG.getVTList(VT, MVT::i32);
+    return DAG.getNode(X86ISD::ADC, SDLoc(N), VTs,
+                       N->getOperand(0), N->getOperand(1),
+                       Flags);
+  }
+
   return SDValue();
 }
 
@@ -35721,7 +35744,7 @@
   case X86ISD::CMOV:        return combineCMov(N, DAG, DCI, Subtarget);
   case ISD::ADD:            return combineAdd(N, DAG, Subtarget);
   case ISD::SUB:            return combineSub(N, DAG, Subtarget);
-  case X86ISD::ADD:         return combineX86ADD(N, DAG, DCI);
+  case X86ISD::SBB:         return combineSBB(N, DAG);
   case X86ISD::ADC:         return combineADC(N, DAG, DCI);
   case ISD::MUL:            return combineMul(N, DAG, DCI, Subtarget);
   case ISD::SHL:

[Attachment #4 (text/plain)]

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