File backport-llvm-r236529 of Package llvm

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r236529 | uweigand | 2015-05-05 21:33:37 +0200 (Tue, 05 May 2015) | 12 lines

[DAGCombiner] Fix ReplaceExtractVectorEltOfLoadWithNarrowedLoad for BE

For little-endian, the function would convert (extract_vector_elt (load X), Y)
to X + Y*sizeof(elt).  For big-endian it would instead use
X + sizeof(vec) - Y*sizeof(elt).  The big-endian case wasn't right since
vector index order always follows memory/array order, even for big-endian.
(Note that the current handling has to be wrong for Y==0 since it would
access beyond the end of the vector.)

Original patch by Richard Sandiford.


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Index: test/CodeGen/SystemZ/vec-extract-01.ll
===================================================================
--- /dev/null
+++ test/CodeGen/SystemZ/vec-extract-01.ll
@@ -0,0 +1,13 @@
+; Verify ReplaceExtractVectorEltOfLoadWithNarrowedLoad fixes
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z13 | FileCheck %s
+
+; Test a memory copy of a v2i32 (via the constant pool).
+define void @f1(<2 x i32> *%dest) {
+; CHECK-LABEL: f1:
+; CHECK: lgrl [[REG:%r[0-5]]], {{[._A-Za-z0-9]}}
+; CHECK: stg [[REG]], 0(%r2)
+; CHECK: br %r14
+  store <2 x i32> <i32 1000000, i32 99999>, <2 x i32> *%dest
+  ret void
+}
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp.orig
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -9328,18 +9328,12 @@ SDValue DAGCombiner::ReplaceExtractVecto
   if (ConstantSDNode *ConstEltNo = dyn_cast<ConstantSDNode>(EltNo)) {
     int Elt = ConstEltNo->getZExtValue();
     unsigned PtrOff = VecEltVT.getSizeInBits() * Elt / 8;
-    if (TLI.isBigEndian())
-      PtrOff = InVecVT.getSizeInBits() / 8 - PtrOff;
     Offset = DAG.getConstant(PtrOff, PtrType);
     MPI = OriginalLoad->getPointerInfo().getWithOffset(PtrOff);
   } else {
     Offset = DAG.getNode(
         ISD::MUL, SDLoc(EVE), EltNo.getValueType(), EltNo,
         DAG.getConstant(VecEltVT.getStoreSize(), EltNo.getValueType()));
-    if (TLI.isBigEndian())
-      Offset = DAG.getNode(
-          ISD::SUB, SDLoc(EVE), EltNo.getValueType(),
-          DAG.getConstant(InVecVT.getStoreSize(), EltNo.getValueType()), Offset);
     MPI = OriginalLoad->getPointerInfo();
   }
   NewPtr = DAG.getNode(ISD::ADD, SDLoc(EVE), PtrType, NewPtr, Offset);