When we vectorize across multiple basic blocks we may vectorize PHINodes that create a cycle. We already break the cycle on phi-nodes, but arithmetic operations are still uplicated. This patch adds code that checks if the operation that we are vectorizing was vectorized during the visit of the operands and uses this value if it can.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186883 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 89 insertions, 3 deletions

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 3502222069..25f7a78f66 100644
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -264,12 +264,16 @@ private:
   /// This is the recursive part of buildTree.
   void buildTree_rec(ArrayRef<Value *> Roots, unsigned Depth);
 
-  /// Vectorizer a single entry in the tree.
+  /// Vectorize a single entry in the tree.
   Value *vectorizeTree(TreeEntry *E);
 
-  /// Vectorizer a single entry in the tree, starting in \p VL.
+  /// Vectorize a single entry in the tree, starting in \p VL.
   Value *vectorizeTree(ArrayRef<Value *> VL);
 
+  /// \returns the pointer to the vectorized value if \p VL is already
+  /// vectorized, or NULL. They may happen in cycles.
+  Value *alreadyVectorized(ArrayRef<Value *> VL);
+
   /// \brief Take the pointer operand from the Load/Store instruction.
   /// \returns NULL if this is not a valid Load/Store instruction.
   static Value *getPointerOperand(Value *I);
@@ -1117,6 +1121,16 @@ Value *BoUpSLP::Gather(ArrayRef<Value *> VL, VectorType *Ty) {
   return Vec;
 }
 
+Value *BoUpSLP::alreadyVectorized(ArrayRef<Value *> VL) {
+  if (ScalarToTreeEntry.count(VL[0])) {
+    int Idx = ScalarToTreeEntry[VL[0]];
+    TreeEntry *En = &VectorizableTree[Idx];
+    if (En->isSame(VL) && En->VectorizedValue)
+      return En->VectorizedValue;
+  }
+  return 0;
+}
+
 Value *BoUpSLP::vectorizeTree(ArrayRef<Value *> VL) {
   if (ScalarToTreeEntry.count(VL[0])) {
     int Idx = ScalarToTreeEntry[VL[0]];
@@ -1206,6 +1220,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
 
       Builder.SetInsertPoint(getLastInstruction(E->Scalars));
       Value *InVec = vectorizeTree(INVL);
+
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
+
       CastInst *CI = dyn_cast<CastInst>(VL0);
       Value *V = Builder.CreateCast(CI->getOpcode(), InVec, VecTy);
       E->VectorizedValue = V;
@@ -1222,9 +1240,12 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       Builder.SetInsertPoint(getLastInstruction(E->Scalars));
       Value *L = vectorizeTree(LHSV);
       Value *R = vectorizeTree(RHSV);
-      Value *V;
+
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
 
       CmpInst::Predicate P0 = dyn_cast<CmpInst>(VL0)->getPredicate();
+      Value *V;
       if (Opcode == Instruction::FCmp)
         V = Builder.CreateFCmp(P0, L, R);
       else
@@ -1245,6 +1266,10 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
       Value *Cond = vectorizeTree(CondVec);
       Value *True = vectorizeTree(TrueVec);
       Value *False = vectorizeTree(FalseVec);
+
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
+      
       Value *V = Builder.CreateSelect(Cond, True, False);
       E->VectorizedValue = V;
       return V;
@@ -1281,6 +1306,9 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
         assert((VL0->getOperand(0) == VL0->getOperand(1)) && "Invalid order");
       }
 
+      if (Value *V = alreadyVectorized(E->Scalars))
+        return V;
+
       BinaryOperator *BinOp = cast<BinaryOperator>(VL0);
       Value *V = Builder.CreateBinOp(BinOp->getOpcode(), LHS, RHS);
       E->VectorizedValue = V;
diff --git a/test/Transforms/SLPVectorizer/X86/cycle_dup.ll b/test/Transforms/SLPVectorizer/X86/cycle_dup.ll
new file mode 100644
index 0000000000..501fae1785
--- /dev/null
+++ b/test/Transforms/SLPVectorizer/X86/cycle_dup.ll
@@ -0,0 +1,58 @@
+; RUN: opt < %s -basicaa -slp-vectorizer -dce -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-macosx10.9.0"
+
+
+; int foo(int *A) {
+;   int r = A[0], g = A[1], b = A[2];
+;   for (int i=0; i < A[13]; i++)
+;     r*=18; g*=19; b*=12;
+;   A[0] = r; A[1] = g; A[2] = b;
+; }
+
+;CHECK-LABEL: @foo
+;CHECK: bitcast i32* %A to <3 x i32>*
+;CHECK-NEXT: load <3 x i32>
+;CHECK: phi <3 x i32>
+;CHECK-NEXT: mul <3 x i32>
+;CHECK-NOT: mul
+;CHECK: phi <3 x i32>
+;CHECK: bitcast i32* %A to <3 x i32>*
+;CHECK-NEXT: store <3 x i32>
+;CHECK-NEXT:ret i32 undef
+define i32 @foo(i32* nocapture %A) {
+entry:
+  %0 = load i32* %A, align 4
+  %arrayidx1 = getelementptr inbounds i32* %A, i64 1
+  %1 = load i32* %arrayidx1, align 4
+  %arrayidx2 = getelementptr inbounds i32* %A, i64 2
+  %2 = load i32* %arrayidx2, align 4
+  %arrayidx3 = getelementptr inbounds i32* %A, i64 13
+  %3 = load i32* %arrayidx3, align 4
+  %cmp18 = icmp sgt i32 %3, 0
+  br i1 %cmp18, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.022 = phi i32 [ %inc, %for.body ], [ 0, %entry ]
+  %b.021 = phi i32 [ %mul5, %for.body ], [ %2, %entry ]
+  %g.020 = phi i32 [ %mul4, %for.body ], [ %1, %entry ]
+  %r.019 = phi i32 [ %mul, %for.body ], [ %0, %entry ]
+  %mul = mul nsw i32 %r.019, 18
+  %mul4 = mul nsw i32 %g.020, 19
+  %mul5 = mul nsw i32 %b.021, 12
+  %inc = add nsw i32 %i.022, 1
+  %cmp = icmp slt i32 %inc, %3
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body, %entry
+  %b.0.lcssa = phi i32 [ %2, %entry ], [ %mul5, %for.body ]
+  %g.0.lcssa = phi i32 [ %1, %entry ], [ %mul4, %for.body ]
+  %r.0.lcssa = phi i32 [ %0, %entry ], [ %mul, %for.body ]
+  store i32 %r.0.lcssa, i32* %A, align 4
+  store i32 %g.0.lcssa, i32* %arrayidx1, align 4
+  store i32 %b.0.lcssa, i32* %arrayidx2, align 4
+  ret i32 undef
+}
+
+