[PATCH] D12591: Fix vector splitting for extract_vector_elt and vector elements of <8-bits.

[Daniel Sanders via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL247128: Fix vector splitting for extract_vector_elt and vector elements of <8-bits. (authored by dsanders).

Changed prior to commit:
  http://reviews.llvm.org/D12591?vs=33914&id=34304#toc

Repository:
  rL LLVM

http://reviews.llvm.org/D12591

Files:
  llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
  llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
  llvm/trunk/test/CodeGen/Mips/llvm-ir/extractelement.ll

Index: llvm/trunk/test/CodeGen/Mips/llvm-ir/extractelement.ll
===================================================================
--- llvm/trunk/test/CodeGen/Mips/llvm-ir/extractelement.ll
+++ llvm/trunk/test/CodeGen/Mips/llvm-ir/extractelement.ll
@@ -0,0 +1,19 @@
+; RUN: llc < %s -march=mips -mcpu=mips2 | FileCheck %s -check-prefix=ALL
+
+; This test triggered a bug in the vector splitting where the type legalizer
+; attempted to extract the element with by storing the vector, then reading
+; an element back. However, the address calculation was:
+;   Base + Index * (EltSizeInBits / 8)
+; and EltSizeInBits was 1. This caused the index to be forgotten.
+define i1 @via_stack_bug(i8 signext %idx) {
+  %1 = extractelement <2 x i1> <i1 false, i1 true>, i8 %idx
+  ret i1 %1
+}
+
+; ALL-LABEL: via_stack_bug:
+; ALL-DAG:       addiu  [[ONE:\$[0-9]+]], $zero, 1
+; ALL-DAG:       sb     [[ONE]], 7($sp)
+; ALL-DAG:       sb     $zero, 6($sp)
+; ALL-DAG:       addiu  [[VPTR:\$[0-9]+]], $sp, 6
+; ALL-DAG:       addu   [[EPTR:\$[0-9]+]], $4, [[VPTR]]
+; ALL:           lbu    $2, 0([[EPTR]])
Index: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -1554,9 +1554,25 @@
   if (CustomLowerNode(N, N->getValueType(0), true))
     return SDValue();
 
-  // Store the vector to the stack.
-  EVT EltVT = VecVT.getVectorElementType();
+  // Make the vector elements byte-addressable if they aren't already.
   SDLoc dl(N);
+  EVT EltVT = VecVT.getVectorElementType();
+  if (EltVT.getSizeInBits() < 8) {
+    SmallVector<SDValue, 4> ElementOps;
+    for (unsigned i = 0; i < VecVT.getVectorNumElements(); ++i) {
+      ElementOps.push_back(DAG.getAnyExtOrTrunc(
+          DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, EltVT, Vec,
+                      DAG.getConstant(i, dl, MVT::i8)),
+          dl, MVT::i8));
+    }
+
+    EltVT = MVT::i8;
+    VecVT = EVT::getVectorVT(*DAG.getContext(), EltVT,
+                             VecVT.getVectorNumElements());
+    Vec = DAG.getNode(ISD::BUILD_VECTOR, dl, VecVT, ElementOps);
+  }
+
+  // Store the vector to the stack.
   SDValue StackPtr = DAG.CreateStackTemporary(VecVT);
   SDValue Store = DAG.getStore(DAG.getEntryNode(), dl, Vec, StackPtr,
                                MachinePointerInfo(), false, false, 0);
Index: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
@@ -1007,6 +1007,8 @@
 
   // Calculate the element offset and add it to the pointer.
   unsigned EltSize = EltVT.getSizeInBits() / 8; // FIXME: should be ABI size.
+  assert(EltSize * 8 == EltVT.getSizeInBits() &&
+         "Converting bits to bytes lost precision");
 
   Index = DAG.getNode(ISD::MUL, dl, Index.getValueType(), Index,
                       DAG.getConstant(EltSize, dl, Index.getValueType()));


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