[DAGCombiner] DAG combine does not know how to combine indexed loads with

sign/zero/any extensions. However a few places were not checking properly the
property of the load and were turning an indexed load into a regular extended
load. Therefore the indexed value was lost during the process and this was
triggering an assertion.

<rdar://problem/16389332>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205923 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -4957,6 +4957,7 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
   // on vectors in one instruction.  We only perform this transformation on
   // scalars.
   if (ISD::isNON_EXTLoad(N0.getNode()) && !VT.isVector() &&
+      ISD::isUNINDEXEDLoad(N0.getNode()) &&
       ((!LegalOperations && !cast<LoadSDNode>(N0)->isVolatile()) ||
        TLI.isLoadExtLegal(ISD::SEXTLOAD, N0.getValueType()))) {
     bool DoXform = true;
@@ -5009,7 +5010,7 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
       TLI.isLoadExtLegal(ISD::SEXTLOAD, N0.getValueType()) &&
       (!LegalOperations && TLI.isOperationLegal(N0.getOpcode(), VT))) {
     LoadSDNode *LN0 = cast<LoadSDNode>(N0.getOperand(0));
-    if (LN0->getExtensionType() != ISD::ZEXTLOAD) {
+    if (LN0->getExtensionType() != ISD::ZEXTLOAD && LN0->isUnindexed()) {
       bool DoXform = true;
       SmallVector<SDNode*, 4> SetCCs;
       if (!N0.hasOneUse())
@@ -5250,6 +5251,7 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
   // on vectors in one instruction.  We only perform this transformation on
   // scalars.
   if (ISD::isNON_EXTLoad(N0.getNode()) && !VT.isVector() &&
+      ISD::isUNINDEXEDLoad(N0.getNode()) &&
       ((!LegalOperations && !cast<LoadSDNode>(N0)->isVolatile()) ||
        TLI.isLoadExtLegal(ISD::ZEXTLOAD, N0.getValueType()))) {
     bool DoXform = true;
@@ -5282,7 +5284,7 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
       TLI.isLoadExtLegal(ISD::ZEXTLOAD, N0.getValueType()) &&
       (!LegalOperations && TLI.isOperationLegal(N0.getOpcode(), VT))) {
     LoadSDNode *LN0 = cast<LoadSDNode>(N0.getOperand(0));
-    if (LN0->getExtensionType() != ISD::SEXTLOAD) {
+    if (LN0->getExtensionType() != ISD::SEXTLOAD && LN0->isUnindexed()) {
       bool DoXform = true;
       SmallVector<SDNode*, 4> SetCCs;
       if (!N0.hasOneUse())
@@ -5478,6 +5480,7 @@ SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
   // on vectors in one instruction.  We only perform this transformation on
   // scalars.
   if (ISD::isNON_EXTLoad(N0.getNode()) && !VT.isVector() &&
+      ISD::isUNINDEXEDLoad(N0.getNode()) &&
       ((!LegalOperations && !cast<LoadSDNode>(N0)->isVolatile()) ||
        TLI.isLoadExtLegal(ISD::EXTLOAD, N0.getValueType()))) {
     bool DoXform = true;

test/CodeGen/ARM64/dagcombiner-indexed-load.ll

@@ -0,0 +1,45 @@
+; RUN: llc -O3 < %s | FileCheck %s
+; Test case for a DAG combiner bug where we combined an indexed load
+; with an extension (sext, zext, or any) into a regular extended load,
+; i.e., dropping the indexed value.
+; <rdar://problem/16389332>
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "arm64-apple-ios"
+
+%class.A = type { i64, i64 }
+%class.C = type { i64 }
+
+; CHECK-LABEL: XX:
+; CHECK: ldr
+define void @XX(%class.A* %K) {
+entry:
+  br i1 undef, label %if.then, label %lor.rhs.i
+
+lor.rhs.i:                                        ; preds = %entry
+  %tmp = load i32* undef, align 4
+  %y.i.i.i = getelementptr inbounds %class.A* %K, i64 0, i32 1
+  %tmp1 = load i64* %y.i.i.i, align 8
+  %U.sroa.3.8.extract.trunc.i = trunc i64 %tmp1 to i32
+  %div11.i = sdiv i32 %U.sroa.3.8.extract.trunc.i, 17
+  %add12.i = add nsw i32 0, %div11.i
+  %U.sroa.3.12.extract.shift.i = lshr i64 %tmp1, 32
+  %U.sroa.3.12.extract.trunc.i = trunc i64 %U.sroa.3.12.extract.shift.i to i32
+  %div15.i = sdiv i32 %U.sroa.3.12.extract.trunc.i, 13
+  %add16.i = add nsw i32 %add12.i, %div15.i
+  %rem.i.i = srem i32 %add16.i, %tmp
+  %idxprom = sext i32 %rem.i.i to i64
+  %arrayidx = getelementptr inbounds %class.C** undef, i64 %idxprom
+  %tobool533 = icmp eq %class.C* undef, null
+  br i1 %tobool533, label %while.end, label %while.body
+
+if.then:                                          ; preds = %entry
+  unreachable
+
+while.body:                                       ; preds = %lor.rhs.i
+  unreachable
+
+while.end:                                        ; preds = %lor.rhs.i
+  %tmp3 = load %class.C** %arrayidx, align 8
+  unreachable
+}