[SelectionDAGBuilder] Set NoUnsignedWrap for inbounds gep and load/store offsets.

[oota-llvm.git] / lib / CodeGen / SelectionDAG / SelectionDAGBuilder.cpp

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 94550d60b36a8e9abf9e72aa98d802d22aead6c5..e446a934554e2c7f97490192fbd7ab366b487cf9 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1329,12 +1329,18 @@ void SelectionDAGBuilder::visitRet(const ReturnInst &I) {
     ComputeValueVTs(TLI, DL, I.getOperand(0)->getType(), ValueVTs, &Offsets);
     unsigned NumValues = ValueVTs.size();
 
+    // An aggregate return value cannot wrap around the address space, so
+    // offsets to its parts don't wrap either.
+    SDNodeFlags Flags;
+    Flags.setNoUnsignedWrap(true);
+
     SmallVector<SDValue, 4> Chains(NumValues);
     for (unsigned i = 0; i != NumValues; ++i) {
       SDValue Add = DAG.getNode(ISD::ADD, getCurSDLoc(),
                                 RetPtr.getValueType(), RetPtr,
                                 DAG.getIntPtrConstant(Offsets[i],
-                                                      getCurSDLoc()));
+                                                      getCurSDLoc()),
+                                &Flags);
       Chains[i] =
         DAG.getStore(Chain, getCurSDLoc(),
                      SDValue(RetOp.getNode(), RetOp.getResNo() + i),
@@ -2994,8 +3000,15 @@ void SelectionDAGBuilder::visitGetElementPtr(const User &I) {
       if (Field) {
         // N = N + Offset
         uint64_t Offset = DL->getStructLayout(StTy)->getElementOffset(Field);
+
+        // In an inbouds GEP with an offset that is nonnegative even when
+        // interpreted as signed, assume there is no unsigned overflow.
+        SDNodeFlags Flags;
+        if (int64_t(Offset) >= 0 && cast<GEPOperator>(I).isInBounds())
+          Flags.setNoUnsignedWrap(true);
+
         N = DAG.getNode(ISD::ADD, dl, N.getValueType(), N,
-                        DAG.getConstant(Offset, dl, N.getValueType()));
+                        DAG.getConstant(Offset, dl, N.getValueType()), &Flags);
       }
 
       Ty = StTy->getElementType(Field);
@@ -3020,7 +3033,14 @@ void SelectionDAGBuilder::visitGetElementPtr(const User &I) {
         SDValue OffsVal = VectorWidth ?
           DAG.getConstant(Offs, dl, MVT::getVectorVT(PtrTy, VectorWidth)) :
           DAG.getConstant(Offs, dl, PtrTy);
-        N = DAG.getNode(ISD::ADD, dl, N.getValueType(), N, OffsVal);
+
+        // In an inbouds GEP with an offset that is nonnegative even when
+        // interpreted as signed, assume there is no unsigned overflow.
+        SDNodeFlags Flags;
+        if (Offs.isNonNegative() && cast<GEPOperator>(I).isInBounds())
+          Flags.setNoUnsignedWrap(true);
+
+        N = DAG.getNode(ISD::ADD, dl, N.getValueType(), N, OffsVal, &Flags);
         continue;
       }
 
@@ -3092,10 +3112,13 @@ void SelectionDAGBuilder::visitAlloca(const AllocaInst &I) {
     Align = 0;
 
   // Round the size of the allocation up to the stack alignment size
-  // by add SA-1 to the size.
+  // by add SA-1 to the size. This doesn't overflow because we're computing
+  // an address inside an alloca.
+  SDNodeFlags Flags;
+  Flags.setNoUnsignedWrap(true);
   AllocSize = DAG.getNode(ISD::ADD, dl,
                           AllocSize.getValueType(), AllocSize,
-                          DAG.getIntPtrConstant(StackAlign - 1, dl));
+                          DAG.getIntPtrConstant(StackAlign - 1, dl), &Flags);
 
   // Mask out the low bits for alignment purposes.
   AllocSize = DAG.getNode(ISD::AND, dl,
@@ -3168,6 +3191,11 @@ void SelectionDAGBuilder::visitLoad(const LoadInst &I) {
   if (isVolatile)
     Root = TLI.prepareVolatileOrAtomicLoad(Root, dl, DAG);
 
+  // An aggregate load cannot wrap around the address space, so offsets to its
+  // parts don't wrap either.
+  SDNodeFlags Flags;
+  Flags.setNoUnsignedWrap(true);
+
   SmallVector<SDValue, 4> Values(NumValues);
   SmallVector<SDValue, 4> Chains(std::min(MaxParallelChains, NumValues));
   EVT PtrVT = Ptr.getValueType();
@@ -3188,7 +3216,8 @@ void SelectionDAGBuilder::visitLoad(const LoadInst &I) {
     }
     SDValue A = DAG.getNode(ISD::ADD, dl,
                             PtrVT, Ptr,
-                            DAG.getConstant(Offsets[i], dl, PtrVT));
+                            DAG.getConstant(Offsets[i], dl, PtrVT),
+                            &Flags);
     SDValue L = DAG.getLoad(ValueVTs[i], dl, Root,
                             A, MachinePointerInfo(SV, Offsets[i]), isVolatile,
                             isNonTemporal, isInvariant, Alignment, AAInfo,
@@ -3243,6 +3272,11 @@ void SelectionDAGBuilder::visitStore(const StoreInst &I) {
   AAMDNodes AAInfo;
   I.getAAMetadata(AAInfo);
 
+  // An aggregate load cannot wrap around the address space, so offsets to its
+  // parts don't wrap either.
+  SDNodeFlags Flags;
+  Flags.setNoUnsignedWrap(true);
+
   unsigned ChainI = 0;
   for (unsigned i = 0; i != NumValues; ++i, ++ChainI) {
     // See visitLoad comments.
@@ -3253,7 +3287,7 @@ void SelectionDAGBuilder::visitStore(const StoreInst &I) {
       ChainI = 0;
     }
     SDValue Add = DAG.getNode(ISD::ADD, dl, PtrVT, Ptr,
-                              DAG.getConstant(Offsets[i], dl, PtrVT));
+                              DAG.getConstant(Offsets[i], dl, PtrVT), &Flags);
     SDValue St = DAG.getStore(Root, dl,
                               SDValue(Src.getNode(), Src.getResNo() + i),
                               Add, MachinePointerInfo(PtrV, Offsets[i]),
@@ -7202,10 +7236,15 @@ TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
     ReturnValues.resize(NumValues);
     SmallVector<SDValue, 4> Chains(NumValues);
 
+    // An aggregate return value cannot wrap around the address space, so
+    // offsets to its parts don't wrap either.
+    SDNodeFlags Flags;
+    Flags.setNoUnsignedWrap(true);
+
     for (unsigned i = 0; i < NumValues; ++i) {
       SDValue Add = CLI.DAG.getNode(ISD::ADD, CLI.DL, PtrVT, DemoteStackSlot,
                                     CLI.DAG.getConstant(Offsets[i], CLI.DL,
-                                                        PtrVT));
+                                                        PtrVT), &Flags);
       SDValue L = CLI.DAG.getLoad(
           RetTys[i], CLI.DL, CLI.Chain, Add,
           MachinePointerInfo::getFixedStack(CLI.DAG.getMachineFunction(),