SLPVectorizer: Fix a bug in the code that generates extracts for values with multiple users.

The external user does not have to be in lane #0. We have to save the lane for each scalar so that we know which vector lane to extract.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181674 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 57 insertions, 9 deletions

diff --git a/lib/Transforms/Vectorize/VecUtils.cpp b/lib/Transforms/Vectorize/VecUtils.cpp
index 6f36c938fa..1362b784f0 100644
--- a/lib/Transforms/Vectorize/VecUtils.cpp
+++ b/lib/Transforms/Vectorize/VecUtils.cpp
@@ -282,6 +282,7 @@ int BoUpSLP::getTreeCost(ArrayRef<Value *> VL) {
         DEBUG(dbgs()<<"SLP: Adding to MustExtract "
               "because of a safe out of tree usage.\n");
         MustExtract.insert(*it);
+        continue;
       }
       if (Lane == -1) Lane = LaneMap[*I];
       if (Lane != LaneMap[*I]) {
@@ -610,6 +611,9 @@ Value *BoUpSLP::Scalarize(ArrayRef<Value *> VL, VectorType *Ty) {
     GatherInstructions.push_back(Vec);
   }
 
+  for (unsigned i = 0; i < Ty->getNumElements(); ++i)
+    VectorizedValues[VL[i]] = Vec;
+
   return Vec;
 }
 
@@ -617,6 +621,7 @@ Value *BoUpSLP::vectorizeTree(ArrayRef<Value *> VL, int VF) {
   Value *V = vectorizeTree_rec(VL, VF);
 
   Instruction *LastInstr = GetLastInstr(VL, VL.size());
+  int LastInstrIdx = InstrIdx[LastInstr];
   IRBuilder<> Builder(LastInstr);
   for (ValueSet::iterator it = MustExtract.begin(), e = MustExtract.end();
        it != e; ++it) {
@@ -625,7 +630,15 @@ Value *BoUpSLP::vectorizeTree(ArrayRef<Value *> VL, int VF) {
     assert(LaneMap.count(I) && "Unable to find the lane for the external use");
     Value *Idx = Builder.getInt32(LaneMap[I]);
     Value *Extract = Builder.CreateExtractElement(Vec, Idx);
-    I->replaceAllUsesWith(Extract);
+    bool Replaced = false;
+    for (Value::use_iterator U = I->use_begin(), UE = U->use_end(); U != UE;
+         ++U) {
+      Instruction *UI = cast<Instruction>(*U);
+      if (UI->getParent() != I->getParent() || InstrIdx[UI] > LastInstrIdx)
+        UI->replaceUsesOfWith(I ,Extract);
+      Replaced = true;
+    }
+    assert(Replaced && "Must replace at least one outside user");
   }
 
   // We moved some instructions around. We have to number them again
@@ -691,7 +704,10 @@ Value *BoUpSLP::vectorizeTree_rec(ArrayRef<Value *> VL, int VF) {
     IRBuilder<> Builder(GetLastInstr(VL, VF));
     CastInst *CI = dyn_cast<CastInst>(VL0);
     Value *V = Builder.CreateCast(CI->getOpcode(), InVec, VecTy);
-    VectorizedValues[VL0] = V;
+
+    for (int i = 0; i < VF; ++i)
+      VectorizedValues[VL[i]] = V;
+
     return V;
   }
   case Instruction::Add:
@@ -723,7 +739,10 @@ Value *BoUpSLP::vectorizeTree_rec(ArrayRef<Value *> VL, int VF) {
     IRBuilder<> Builder(GetLastInstr(VL, VF));
     BinaryOperator *BinOp = cast<BinaryOperator>(VL0);
     Value *V = Builder.CreateBinOp(BinOp->getOpcode(), RHS,LHS);
-    VectorizedValues[VL0] = V;
+
+    for (int i = 0; i < VF; ++i)
+      VectorizedValues[VL[i]] = V;
+
     return V;
   }
   case Instruction::Load: {
@@ -740,7 +759,10 @@ Value *BoUpSLP::vectorizeTree_rec(ArrayRef<Value *> VL, int VF) {
                                           VecTy->getPointerTo());
     LI = Builder.CreateLoad(VecPtr);
     LI->setAlignment(Alignment);
-    VectorizedValues[VL0] = LI;
+
+    for (int i = 0; i < VF; ++i)
+      VectorizedValues[VL[i]] = LI;
+
     return LI;
   }
   case Instruction::Store: {
@@ -763,9 +785,7 @@ Value *BoUpSLP::vectorizeTree_rec(ArrayRef<Value *> VL, int VF) {
     return 0;
   }
   default:
-    Value *S = Scalarize(VL, VecTy);
-    VectorizedValues[VL0] = S;
-    return S;
+    return Scalarize(VL, VecTy);
   }
 }
 
diff --git a/test/Transforms/SLPVectorizer/X86/diamond.ll b/test/Transforms/SLPVectorizer/X86/diamond.ll
index 49c8712d20..8959b0d9ee 100644
--- a/test/Transforms/SLPVectorizer/X86/diamond.ll
+++ b/test/Transforms/SLPVectorizer/X86/diamond.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -basicaa -slp-vectorizer -dce -S -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7-avx | FileCheck %s
+; RUN: opt < %s -basicaa -slp-vectorizer -S -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7-avx | FileCheck %s
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.8.0"
@@ -74,6 +74,34 @@ entry:
   %add20 = mul i32 %3, %mul238
   %arrayidx21 = getelementptr inbounds i32* %B, i64 3
   store i32 %add20, i32* %arrayidx21, align 4
-  ret i32 %0  ;<--------- This value has multiple users and can't be vectorized.
+  ret i32 %0  ;<--------- This value has multiple users
 }
 
+; In this example we have an external user that is not the first element in the vector.
+; CHECK: @extr_user1
+; CHECK: store <4 x i32>
+; CHECK-NEXT: extractelement <4 x i32>
+; CHECK: ret
+define i32 @extr_user1(i32* noalias nocapture %B, i32* noalias nocapture %A, i32 %n, i32 %m) {
+entry:
+  %0 = load i32* %A, align 4
+  %mul238 = add i32 %m, %n
+  %add = mul i32 %0, %mul238
+  store i32 %add, i32* %B, align 4
+  %arrayidx4 = getelementptr inbounds i32* %A, i64 1
+  %1 = load i32* %arrayidx4, align 4
+  %add8 = mul i32 %1, %mul238
+  %arrayidx9 = getelementptr inbounds i32* %B, i64 1
+  store i32 %add8, i32* %arrayidx9, align 4
+  %arrayidx10 = getelementptr inbounds i32* %A, i64 2
+  %2 = load i32* %arrayidx10, align 4
+  %add14 = mul i32 %2, %mul238
+  %arrayidx15 = getelementptr inbounds i32* %B, i64 2
+  store i32 %add14, i32* %arrayidx15, align 4
+  %arrayidx16 = getelementptr inbounds i32* %A, i64 3
+  %3 = load i32* %arrayidx16, align 4
+  %add20 = mul i32 %3, %mul238
+  %arrayidx21 = getelementptr inbounds i32* %B, i64 3
+  store i32 %add20, i32* %arrayidx21, align 4
+  ret i32 %1  ;<--------- This value has multiple users
+}