[CostModel][X86] getArithmeticInstrCost - move SLM reduceVMULWidth co…

…st handling into the generic MUL handling

This is still SLM specific atm, but converting this to more closely match the codegen from reduceVMULWidth should be straightforward

llvm/lib/Target/X86/X86TargetTransformInfo.cpp

@@ -254,6 +254,7 @@ InstructionCost X86TTIImpl::getArithmeticInstrCost(
     unsigned Op1MinSize = BaseT::minRequiredElementSize(Args[0], Op1Signed);
     unsigned Op2MinSize = BaseT::minRequiredElementSize(Args[1], Op2Signed);
     unsigned OpMinSize = std::max(Op1MinSize, Op2MinSize);
+    bool SignedMode = Op1Signed || Op2Signed;
 
     // If both are representable as i15 and at least one is constant,
     // zero-extended, or sign-extended from vXi16 (or less pre-SSE41) then we
@@ -275,6 +276,20 @@ InstructionCost X86TTIImpl::getArithmeticInstrCost(
         LT.second =
             MVT::getVectorVT(MVT::i16, 2 * LT.second.getVectorNumElements());
     }
+
+    // Check if the vXi32 operands can be shrunk into a smaller datatype.
+    // This should match the codegen from reduceVMULWidth.
+    // TODO: Make this generic (!ST->SSE41 || ST->isPMULLDSlow()).
+    if (ST->useSLMArithCosts() && LT.second == MVT::v4i32) {
+      if (OpMinSize <= 7)
+        return LT.first * 3; // pmullw/sext
+      if (!SignedMode && OpMinSize <= 8)
+        return LT.first * 3; // pmullw/zext
+      if (OpMinSize <= 15)
+        return LT.first * 5; // pmullw/pmulhw/pshuf
+      if (!SignedMode && OpMinSize <= 16)
+        return LT.first * 5; // pmullw/pmulhw/pshuf
+    }
   }
 
   // Vector multiply by pow2 will be simplified to shifts.
@@ -372,32 +387,10 @@ InstructionCost X86TTIImpl::getArithmeticInstrCost(
     { ISD::SUB,   MVT::v2i64, {  4 } },
   };
 
-  if (ST->useSLMArithCosts()) {
-    if (Args.size() == 2 && ISD == ISD::MUL && LT.second == MVT::v4i32) {
-      // Check if the operands can be shrinked into a smaller datatype.
-      // TODO: Merge this into generiic vXi32 MUL patterns above.
-      bool Op1Signed = false;
-      unsigned Op1MinSize = BaseT::minRequiredElementSize(Args[0], Op1Signed);
-      bool Op2Signed = false;
-      unsigned Op2MinSize = BaseT::minRequiredElementSize(Args[1], Op2Signed);
-
-      bool SignedMode = Op1Signed || Op2Signed;
-      unsigned OpMinSize = std::max(Op1MinSize, Op2MinSize);
-
-      if (OpMinSize <= 7)
-        return LT.first * 3; // pmullw/sext
-      if (!SignedMode && OpMinSize <= 8)
-        return LT.first * 3; // pmullw/zext
-      if (OpMinSize <= 15)
-        return LT.first * 5; // pmullw/pmulhw/pshuf
-      if (!SignedMode && OpMinSize <= 16)
-        return LT.first * 5; // pmullw/pmulhw/pshuf
-    }
-
+  if (ST->useSLMArithCosts())
     if (const auto *Entry = CostTableLookup(SLMCostTable, ISD, LT.second))
       if (auto KindCost = Entry->Cost[CostKind])
         return LT.first * KindCost.value();
-  }
 
   static const CostKindTblEntry AVX512BWUniformConstCostTable[] = {
     { ISD::SHL,  MVT::v64i8, { 2 } }, // psllw + pand.