Revert "Add support for combining GEPs across PHI nodes"

This reverts commit r209755.

it was the real cause of the libc++ build failure.

llvm-svn: 209775

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 80eec1b..4c36887 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1220,85 +1220,6 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
     if (MadeChange) return &GEP;
   }
 
-  // Check to see if the inputs to the PHI node are getelementptr instructions.
-  if (PHINode *PN = dyn_cast<PHINode>(PtrOp)) {
-    GetElementPtrInst *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0));
-    if (!Op1)
-      return nullptr;
-
-    signed DI = -1;
-
-    for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) {
-      GetElementPtrInst *Op2 = dyn_cast<GetElementPtrInst>(*I);
-      if (!Op2 || Op1->getNumOperands() != Op2->getNumOperands())
-        return nullptr;
-
-      for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) {
-        if (Op1->getOperand(J)->getType() != Op2->getOperand(J)->getType())
-          return nullptr;
-
-        if (Op1->getOperand(J) != Op2->getOperand(J)) {
-          if (DI == -1) {
-            // We have not seen any differences yet in the GEPs feeding the
-            // PHI yet, so we record this one if it is allowed to be a
-            // variable.
-
-            // The first two arguments can vary for any GEP, the rest have to be
-            // static for struct slots
-            if (J > 1) {
-              SmallVector<Value*, 8> Idxs(GEP.idx_begin(), GEP.idx_begin()+J);
-              Type *Ty =
-                GetElementPtrInst::getIndexedType(Op1->getOperand(0)->getType(),
-                                                  Idxs);
-              if (Ty->isStructTy())
-                return nullptr;
-            }
-
-            DI = J;
-          } else {
-            // The GEP is different by more than one input. While this could be
-            // extended to support GEPs that vary by more than one variable it
-            // doesn't make sense since it greatly increases the complexity and
-            // would result in an R+R+R addressing mode which no backend
-            // directly supports and would need to be broken into several
-            // simpler instructions anyway.
-            return nullptr;
-          }
-        }
-      }
-    }
-
-    GetElementPtrInst *NewGEP = cast<GetElementPtrInst>(Op1->clone());
-
-    if (DI == -1) {
-      // All the GEPs feeding the PHI are identical. Clone one down into our
-      // BB so that it can be merged with the current GEP.
-      GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(),
-                                            NewGEP);
-    } else {
-      // All the GEPs feeding the PHI differ at a single offset. Clone a GEP
-      // into the current block so it can be merged, and create a new PHI to
-      // set that index.
-      Instruction *InsertPt = Builder->GetInsertPoint();
-      Builder->SetInsertPoint(PN);
-      PHINode *NewPN = Builder->CreatePHI(Op1->getOperand(DI)->getType(),
-                                          PN->getNumOperands());
-      Builder->SetInsertPoint(InsertPt);
-
-      for (auto &I : PN->operands())
-        NewPN->addIncoming(cast<GEPOperator>(I)->getOperand(DI),
-                           PN->getIncomingBlock(I));
-
-      NewGEP->setOperand(DI, NewPN);
-      GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(),
-                                            NewGEP);
-      NewGEP->setOperand(DI, NewPN);
-    }
-
-    GEP.setOperand(0, NewGEP);
-    PtrOp = NewGEP;
-  }
-
   // Combine Indices - If the source pointer to this getelementptr instruction
   // is a getelementptr instruction, combine the indices of the two
   // getelementptr instructions into a single instruction.

diff --git a/llvm/test/Transforms/InstCombine/gepphigep.ll b/llvm/test/Transforms/InstCombine/gepphigep.ll
deleted file mode 100644 (file)
index 9aab609..0000000
--- a/llvm/test/Transforms/InstCombine/gepphigep.ll
+++ /dev/null
@@ -1,56 +0,0 @@
-; RUN: opt -instcombine -S  < %s | FileCheck %s
-
-%struct1 = type { %struct2*, i32, i32, i32 }
-%struct2 = type { i32, i32 }
-
-define i32 @test1(%struct1* %dm, i1 %tmp4, i64 %tmp9, i64 %tmp19) {
-bb:
-  %tmp = getelementptr inbounds %struct1* %dm, i64 0, i32 0
-  %tmp1 = load %struct2** %tmp, align 8
-  br i1 %tmp4, label %bb1, label %bb2
-
-bb1:
-  %tmp10 = getelementptr inbounds %struct2* %tmp1, i64 %tmp9
-  %tmp11 = getelementptr inbounds %struct2* %tmp10, i64 0, i32 0
-  store i32 0, i32* %tmp11, align 4
-  br label %bb3
-
-bb2:
-  %tmp20 = getelementptr inbounds %struct2* %tmp1, i64 %tmp19
-  %tmp21 = getelementptr inbounds %struct2* %tmp20, i64 0, i32 0
-  store i32 0, i32* %tmp21, align 4
-  br label %bb3
-
-bb3:
-  %phi = phi %struct2* [ %tmp10, %bb1 ], [ %tmp20, %bb2 ]
-  %tmp24 = getelementptr inbounds %struct2* %phi, i64 0, i32 1
-  %tmp25 = load i32* %tmp24, align 4
-  ret i32 %tmp25
-
-; CHECK-LABEL: @test1(
-; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp9, i32 0
-; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp19, i32 0
-; CHECK: %[[PHI:[0-9A-Za-z]+]] = phi i64 [ %tmp9, %bb1 ], [ %tmp19, %bb2 ]
-; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %[[PHI]], i32 1
-
-}
-
-define i32 @test2(%struct1* %dm, i1 %tmp4, i64 %tmp9, i64 %tmp19) {
-bb:
-  %tmp = getelementptr inbounds %struct1* %dm, i64 0, i32 0
-  %tmp1 = load %struct2** %tmp, align 8
-  %tmp10 = getelementptr inbounds %struct2* %tmp1, i64 %tmp9
-  %tmp11 = getelementptr inbounds %struct2* %tmp10, i64 0, i32 0
-  store i32 0, i32* %tmp11, align 4
-  %tmp20 = getelementptr inbounds %struct2* %tmp1, i64 %tmp19
-  %tmp21 = getelementptr inbounds %struct2* %tmp20, i64 0, i32 0
-  store i32 0, i32* %tmp21, align 4
-  %tmp24 = getelementptr inbounds %struct2* %tmp10, i64 0, i32 1
-  %tmp25 = load i32* %tmp24, align 4
-  ret i32 %tmp25
-
-; CHECK-LABEL: @test2(
-; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp9, i32 0
-; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp19, i32 0
-; CHECK: getelementptr inbounds %struct2* %tmp1, i64 %tmp9, i32 1
-}