[Codegen] Revert rL354676/rL354677 and followups - introduced PR43446 miscompile

This reverts https://reviews.llvm.org/D58468
(rL354676, 44037d7a6377ec8e5542cced73583283334b516b),
and all and any follow-ups to that code block.

https://bugs.llvm.org/show_bug.cgi?id=43446

(cherry picked from commit d20907d1de89bf63b589fadd8c096d4895e47fba)

1 files changed, 0 insertions, 27 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index e5bc08b9280..8ff04797c8d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -16510,33 +16510,6 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
           CombineTo(ST1, ST1->getChain());
           return SDValue();
         }
-
-        // If ST stores to a subset of preceding store's write set, we may be
-        // able to fold ST's value into the preceding stored value. As we know
-        // the other uses of ST1's chain are unconcerned with ST, this folding
-        // will not affect those nodes.
-        int64_t BitOffset;
-        if (ChainBase.contains(DAG, ChainBitSize, STBase, STBitSize,
-                               BitOffset)) {
-          SDValue ChainValue = ST1->getValue();
-          if (auto *C1 = dyn_cast<ConstantSDNode>(ChainValue)) {
-            if (auto *C = dyn_cast<ConstantSDNode>(Value)) {
-              APInt Val = C1->getAPIntValue();
-              APInt InsertVal = C->getAPIntValue().zextOrTrunc(STBitSize);
-              // FIXME: Handle Big-endian mode.
-              if (!DAG.getDataLayout().isBigEndian()) {
-                Val.insertBits(InsertVal, BitOffset);
-                SDValue NewSDVal =
-                    DAG.getConstant(Val, SDLoc(C), ChainValue.getValueType(),
-                                    C1->isTargetOpcode(), C1->isOpaque());
-                SDNode *NewST1 = DAG.UpdateNodeOperands(
-                    ST1, ST1->getChain(), NewSDVal, ST1->getOperand(2),
-                    ST1->getOperand(3));
-                return CombineTo(ST, SDValue(NewST1, 0));
-              }
-            }
-          }
-        } // End ST subset of ST1 case.
       }
     }
   }