[PATCH] [ARM] Fix issue with SMLAL (Signed Multiply Accumulate Long) lowering

[Jyoti Allur]

Hi Tim, 
You were right, the original issue existed with the buggy opcode checking which is now corrected without additional checks.
Thanks.


http://reviews.llvm.org/D6998

Files:
  ../llvm/lib/Target/ARM/ARMISelLowering.cpp
  ../llvm/test/CodeGen/ARM/longMAC.ll

Index: ../llvm/lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- ../llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ ../llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -8065,7 +8065,6 @@
   unsigned FinalOpc = (Opc == ISD::SMUL_LOHI) ? ARMISD::SMLAL : ARMISD::UMLAL;
 
   // Figure out the high and low input values to the MLAL node.
-  SDValue* HiMul = &MULOp;
   SDValue* HiAdd = nullptr;
   SDValue* LoMul = nullptr;
   SDValue* LowAdd = nullptr;
@@ -8075,12 +8074,15 @@
   else
     HiAdd = &AddeOp0;
 
+  // When both operands of ADDC are a result from different ISD::SMUL_LOHI,
+  // make sure LoMul and LowAdd are taken from correct ISD::SMUL_LOHI result.
 
-  if (AddcOp0->getOpcode() == Opc) {
+  if (AddcOp0 == MULOp.getValue(0)) {
     LoMul = &AddcOp0;
     LowAdd = &AddcOp1;
   }
-  if (AddcOp1->getOpcode() == Opc) {
+
+  if (AddcOp1 == MULOp.getValue(1)) {
     LoMul = &AddcOp1;
     LowAdd = &AddcOp0;
   }
@@ -8088,9 +8090,6 @@
   if (!LoMul)
     return SDValue();
 
-  if (LoMul->getNode() != HiMul->getNode())
-    return SDValue();
-
   // Create the merged node.
   SelectionDAG &DAG = DCI.DAG;
 
Index: ../llvm/test/CodeGen/ARM/longMAC.ll
===================================================================
--- ../llvm/test/CodeGen/ARM/longMAC.ll
+++ ../llvm/test/CodeGen/ARM/longMAC.ll
@@ -75,3 +75,31 @@
   %add = add i64 %mul, %c
   ret i64 %add
 }
+
+define i64 @MACLongTest6(i32 %a, i32 %b, i32 %c, i32 %d) {
+;CHECK-LABEL: MACLongTest6:
+;CHECK: smull   r12, lr, r1, r0
+;CHECK: smlal   r12, lr, r3, r2
+  %conv = sext i32 %a to i64
+  %conv1 = sext i32 %b to i64
+  %mul = mul nsw i64 %conv1, %conv
+  %conv2 = sext i32 %c to i64
+  %conv3 = sext i32 %d to i64
+  %mul4 = mul nsw i64 %conv3, %conv2
+  %add = add nsw i64 %mul4, %mul
+  ret i64 %add
+}
+
+define i64 @MACLongTest7(i64 %acc, i32 %lhs, i32 %rhs) {
+;CHECK-LABEL: MACLongTest7:
+;CHECK-NOT: smlal
+  %conv = sext i32 %lhs to i64
+  %conv1 = sext i32 %rhs to i64
+  %mul = mul nsw i64 %conv1, %conv
+  %shl = shl i64 %mul, 32
+  %shr = lshr i64 %mul, 32
+  %or = or i64 %shl, %shr
+  %add = add i64 %or, %acc
+  ret i64 %add
+}
+

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