Combine to vpdpbusd when operand is constant and small enough.

Differential Revision: https://reviews.llvm.org/D116363

Author: LuoYuanke

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -9252,8 +9252,13 @@ static bool isFoldableUseOfShuffle(SDNode *N) {
       return true;
     if (Opc == ISD::BITCAST) // Ignore bitcasts
       return isFoldableUseOfShuffle(U);
-    if (N->hasOneUse())
+    if (N->hasOneUse()) {
+      // TODO, there may be some general way to know if a SDNode can
+      // be folded. We now only know whether an MI is foldable.
+      if (Opc == X86ISD::VPDPBUSD && U->getOperand(2).getNode() != N)
+        return false;
       return true;
+    }
   }
   return false;
 }
@@ -41973,17 +41978,14 @@ static bool detectExtMul(SelectionDAG &DAG, const SDValue &Mul, SDValue &Op0,
   if (Op0.getOpcode() == ISD::SIGN_EXTEND)
     std::swap(Op0, Op1);
 
-  if (Op0.getOpcode() != ISD::ZERO_EXTEND)
-    return false;
-
   auto IsFreeTruncation = [](SDValue &Op) -> bool {
     if ((Op.getOpcode() == ISD::ZERO_EXTEND ||
          Op.getOpcode() == ISD::SIGN_EXTEND) &&
         Op.getOperand(0).getScalarValueSizeInBits() <= 8)
       return true;
 
-    // TODO: Support contant value.
-    return false;
+    auto *BV = dyn_cast<BuildVectorSDNode>(Op);
+    return (BV && BV->isConstant());
   };
 
   // (dpbusd (zext a), (sext, b)). Since the first operand should be unsigned

llvm/lib/Target/X86/X86PartialReduction.cpp

@@ -76,9 +76,6 @@ static bool matchVPDPBUSDPattern(const X86Subtarget *ST, BinaryOperator *Mul,
   if (isa<SExtInst>(LHS))
     std::swap(LHS, RHS);
 
-  if (!isa<ZExtInst>(LHS))
-    return false;
-
   auto IsFreeTruncation = [&](Value *Op) {
     if (auto *Cast = dyn_cast<CastInst>(Op)) {
       if (Cast->getParent() == Mul->getParent() &&
@@ -87,8 +84,8 @@ static bool matchVPDPBUSDPattern(const X86Subtarget *ST, BinaryOperator *Mul,
           Cast->getOperand(0)->getType()->getScalarSizeInBits() <= 8)
         return true;
     }
-    // TODO: Support constant in ISel.
-    return false;
+
+    return isa<Constant>(Op);
   };
 
   // (dpbusd (zext a), (sext, b)). Since the first operand should be unsigned