The patch fixes (base, index, offset) match.

Summary:
Instead of matching:
  (a + i) + 1 -> (a + i, undef, 1)
Now it matches:
  (a + i) + 1 -> (a, i, 1)

Reviewers: rengolin

Differential Revision: http://reviews.llvm.org/D26367

From: Evgeny Stupachenko <[email protected]>
llvm-svn: 291012

Author: evstupac

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -4277,7 +4277,8 @@ struct BaseIndexOffset {
   }
 
   /// Parses tree in Ptr for base, index, offset addresses.
-  static BaseIndexOffset match(SDValue Ptr, SelectionDAG &DAG) {
+  static BaseIndexOffset match(SDValue Ptr, SelectionDAG &DAG,
+                               int64_t PartialOffset = 0) {
     bool IsIndexSignExt = false;
 
     // Split up a folded GlobalAddress+Offset into its component parts.
@@ -4286,7 +4287,7 @@ struct BaseIndexOffset {
         return BaseIndexOffset(DAG.getGlobalAddress(GA->getGlobal(),
                                                     SDLoc(GA),
                                                     GA->getValueType(0),
-                                                    /*Offset=*/0,
+                                                    /*Offset=*/PartialOffset,
                                                     /*isTargetGA=*/false,
                                                     GA->getTargetFlags()),
                                SDValue(),
@@ -4298,14 +4299,13 @@ struct BaseIndexOffset {
     // instruction, then it could be just the BASE or everything else we don't
     // know how to handle. Just use Ptr as BASE and give up.
     if (Ptr->getOpcode() != ISD::ADD)
-      return BaseIndexOffset(Ptr, SDValue(), 0, IsIndexSignExt);
+      return BaseIndexOffset(Ptr, SDValue(), PartialOffset, IsIndexSignExt);
 
     // We know that we have at least an ADD instruction. Try to pattern match
     // the simple case of BASE + OFFSET.
     if (isa<ConstantSDNode>(Ptr->getOperand(1))) {
       int64_t Offset = cast<ConstantSDNode>(Ptr->getOperand(1))->getSExtValue();
-      return  BaseIndexOffset(Ptr->getOperand(0), SDValue(), Offset,
-                              IsIndexSignExt);
+      return match(Ptr->getOperand(0), DAG, Offset + PartialOffset);
     }
 
     // Inside a loop the current BASE pointer is calculated using an ADD and a
@@ -4314,7 +4314,7 @@ struct BaseIndexOffset {
     //          (i64 mul (i64 %induction_var)
     //                   (i64 %element_size)))
     if (Ptr->getOperand(1)->getOpcode() == ISD::MUL)
-      return BaseIndexOffset(Ptr, SDValue(), 0, IsIndexSignExt);
+      return BaseIndexOffset(Ptr, SDValue(), PartialOffset, IsIndexSignExt);
 
     // Look at Base + Index + Offset cases.
     SDValue Base = Ptr->getOperand(0);
@@ -4328,14 +4328,14 @@ struct BaseIndexOffset {
 
     // Either the case of Base + Index (no offset) or something else.
     if (IndexOffset->getOpcode() != ISD::ADD)
-      return BaseIndexOffset(Base, IndexOffset, 0, IsIndexSignExt);
+      return BaseIndexOffset(Base, IndexOffset, PartialOffset, IsIndexSignExt);
 
     // Now we have the case of Base + Index + offset.
     SDValue Index = IndexOffset->getOperand(0);
     SDValue Offset = IndexOffset->getOperand(1);
 
     if (!isa<ConstantSDNode>(Offset))
-      return BaseIndexOffset(Ptr, SDValue(), 0, IsIndexSignExt);
+      return BaseIndexOffset(Ptr, SDValue(), PartialOffset, IsIndexSignExt);
 
     // Ignore signextends.
     if (Index->getOpcode() == ISD::SIGN_EXTEND) {
@@ -4344,7 +4344,7 @@ struct BaseIndexOffset {
     } else IsIndexSignExt = false;
 
     int64_t Off = cast<ConstantSDNode>(Offset)->getSExtValue();
-    return BaseIndexOffset(Base, Index, Off, IsIndexSignExt);
+    return BaseIndexOffset(Base, Index, Off + PartialOffset, IsIndexSignExt);
   }
 };
 } // namespace

llvm/test/CodeGen/X86/MergeConsecutiveStores.ll

@@ -370,6 +370,40 @@ define void @MergeLoadStoreBaseIndexOffset(i64* %a, i8* %b, i8* %c, i32 %n) {
   ret void
 }
 
+; Make sure that we merge the consecutive load/store sequence below and use a
+; word (16 bit) instead of a byte copy for complicated address calculation.
+; .
+; CHECK-LABEL: MergeLoadStoreBaseIndexOffsetComplicated:
+; BWON: movzwl   (%{{.*}},%{{.*}}), %e[[REG:[a-z]+]]
+; BWOFF: movw    (%{{.*}},%{{.*}}), %[[REG:[a-z]+]]
+; CHECK: movw    %[[REG]], (%{{.*}})
+define void @MergeLoadStoreBaseIndexOffsetComplicated(i8* %a, i8* %b, i8* %c, i64 %n) {
+  br label %1
+
+; <label>:1
+  %.09 = phi i64 [ 0, %0 ], [ %13, %1 ]
+  %.08 = phi i8* [ %b, %0 ], [ %12, %1 ]
+  %2 = load i8, i8* %.08, align 1
+  %3 = sext i8 %2 to i64
+  %4 = getelementptr inbounds i8, i8* %c, i64 %3
+  %5 = load i8, i8* %4, align 1
+  %6 = add nsw i64 %3, 1
+  %7 = getelementptr inbounds i8, i8* %c, i64 %6
+  %8 = load i8, i8* %7, align 1
+  %9 = getelementptr inbounds i8, i8* %a, i64 %.09
+  store i8 %5, i8* %9, align 1
+  %10 = or i64 %.09, 1
+  %11 = getelementptr inbounds i8, i8* %a, i64 %10
+  store i8 %8, i8* %11, align 1
+  %12 = getelementptr inbounds i8, i8* %.08, i64 1
+  %13 = add nuw nsw i64 %.09, 2
+  %14 = icmp slt i64 %13, %n
+  br i1 %14, label %1, label %15
+
+; <label>:15
+  ret void
+}
+
 ; Make sure that we merge the consecutive load/store sequence below and use a
 ; word (16 bit) instead of a byte copy even if there are intermediate sign
 ; extensions.