[SDAG] Use correct alignments on expanded vector trunc-store/ext-loads

When expanding a truncating store or extending load using vector extracts or
inserts and scalar stores and loads, we were giving each of these scalar stores
or loads the same alignment as the original vector operation. While this will
often be right (most vector operations, especially those produced by
autovectorization, have the alignment of the underlying scalar type), the
vector operation could certainly have a larger alignment.

No test case (yet); noticed by inspection.

llvm-svn: 230175

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 3a8c276..9abbe73 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -512,7 +512,8 @@ SDValue VectorLegalizer::ExpandLoad(SDValue Op) {
         ScalarLoad = DAG.getLoad(WideVT, dl, Chain, BasePTR,
                                  LD->getPointerInfo().getWithOffset(Offset),
                                  LD->isVolatile(), LD->isNonTemporal(),
-                                 LD->isInvariant(), LD->getAlignment(),
+                                 LD->isInvariant(),
+                                 MinAlign(LD->getAlignment(), Offset),
                                  LD->getAAInfo());
       } else {
         EVT LoadVT = WideVT;
@@ -524,7 +525,8 @@ SDValue VectorLegalizer::ExpandLoad(SDValue Op) {
                                     LD->getPointerInfo().getWithOffset(Offset),
                                     LoadVT, LD->isVolatile(),
                                     LD->isNonTemporal(), LD->isInvariant(),
-                                    LD->getAlignment(), LD->getAAInfo());
+                                    MinAlign(LD->getAlignment(), Offset),
+                                    LD->getAAInfo());
       }
 
       RemainingBytes -= LoadBytes;
@@ -595,7 +597,7 @@ SDValue VectorLegalizer::ExpandLoad(SDValue Op) {
                 Chain, BasePTR, LD->getPointerInfo().getWithOffset(Idx * Stride),
                 SrcVT.getScalarType(),
                 LD->isVolatile(), LD->isNonTemporal(), LD->isInvariant(),
-                LD->getAlignment(), LD->getAAInfo());
+                MinAlign(LD->getAlignment(), Idx * Stride), LD->getAAInfo());
 
       BasePTR = DAG.getNode(ISD::ADD, dl, BasePTR.getValueType(), BasePTR,
                          DAG.getConstant(Stride, BasePTR.getValueType()));
@@ -654,7 +656,8 @@ SDValue VectorLegalizer::ExpandStore(SDValue Op) {
     // This scalar TruncStore may be illegal, but we legalize it later.
     SDValue Store = DAG.getTruncStore(Chain, dl, Ex, BasePTR,
                ST->getPointerInfo().getWithOffset(Idx*Stride), MemSclVT,
-               isVolatile, isNonTemporal, Alignment, AAInfo);
+               isVolatile, isNonTemporal, MinAlign(Alignment, Idx*Stride),
+               AAInfo);
 
     BasePTR = DAG.getNode(ISD::ADD, dl, BasePTR.getValueType(), BasePTR,
                                DAG.getConstant(Stride, BasePTR.getValueType()));