Rewrite areNonVolatileConsecutiveLoads to use BaseIndexOffset

Relanding after rewriting undef.ll test to avoid host-dependant
endianness.

As discussed in D34087, rewrite areNonVolatileConsecutiveLoads using
generic checks. Also, propagate missing local handling from there to
BaseIndexOffset checks.

Tests of note:

  * test/CodeGen/X86/build-vector* - Improved.
  * test/CodeGen/BPF/undef.ll - Improved store alignment allows an
    additional store merge

  * test/CodeGen/X86/clear_upper_vector_element_bits.ll - This is a
    case we already do not handle well. Here, the DAG is improved, but
    scheduling causes a code size degradation.

Reviewers: RKSimon, craig.topper, spatel, andreadb, filcab

Subscribers: nemanjai, llvm-commits

Differential Revision: https://reviews.llvm.org/D34472

llvm-svn: 307114

1 files changed, 12 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
index 14b804eef22..0d69441ebb7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp
@@ -60,12 +60,18 @@ BaseIndexOffset BaseIndexOffset::match(SDValue Ptr, const SelectionDAG &DAG) {
   int64_t Offset = 0;
   bool IsIndexSignExt = false;
 
-  // Consume constant adds
-  while (Base->getOpcode() == ISD::ADD &&
-         isa<ConstantSDNode>(Base->getOperand(1))) {
-    int64_t POffset = cast<ConstantSDNode>(Base->getOperand(1))->getSExtValue();
-    Offset += POffset;
-    Base = Base->getOperand(0);
+  // Consume constant adds & ors with appropriate masking.
+  while (Base->getOpcode() == ISD::ADD || Base->getOpcode() == ISD::OR) {
+    if (auto *C = dyn_cast<ConstantSDNode>(Base->getOperand(1))) {
+      // Only consider ORs which act as adds.
+      if (Base->getOpcode() == ISD::OR &&
+          !DAG.MaskedValueIsZero(Base->getOperand(0), C->getAPIntValue()))
+        break;
+      Offset += C->getSExtValue();
+      Base = Base->getOperand(0);
+      continue;
+    }
+    break;
   }
 
   if (Base->getOpcode() == ISD::ADD) {