Fix a bug in the vectorization of wide load/store operations.

We used a SCEV to detect that A[X] is consecutive. We assumed that X was
the induction variable. But X can be any expression that uses the induction
for example: X = i + 2;



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166388 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 44 insertions, 4 deletions

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 5a79c33bdc..1b6011bd1a 100644
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -740,10 +740,15 @@ SingleBlockLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
           break;
         }
 
+        // The last index does not have to be the induction. It can be
+        // consecutive and be a function of the index. For example A[I+1];
+        unsigned NumOperands = Gep->getNumOperands();
+        Value *LastIndex = getVectorValue(Gep->getOperand(NumOperands -1));
+        LastIndex = Builder.CreateExtractElement(LastIndex, Builder.getInt32(0));
+
         // Create the new GEP with the new induction variable.
         GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
-        unsigned NumOperands = Gep->getNumOperands();
-        Gep2->setOperand(NumOperands - 1, Induction);
+        Gep2->setOperand(NumOperands - 1, LastIndex);
         Ptr = Builder.Insert(Gep2);
         Ptr = Builder.CreateBitCast(Ptr, StTy->getPointerTo());
         Value *Val = getVectorValue(SI->getValueOperand());
@@ -764,10 +769,15 @@ SingleBlockLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
           break;
         }
 
+        // The last index does not have to be the induction. It can be
+        // consecutive and be a function of the index. For example A[I+1];
+        unsigned NumOperands = Gep->getNumOperands();
+        Value *LastIndex = getVectorValue(Gep->getOperand(NumOperands -1));
+        LastIndex = Builder.CreateExtractElement(LastIndex, Builder.getInt32(0));
+
         // Create the new GEP with the new induction variable.
         GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
-        unsigned NumOperands = Gep->getNumOperands();
-        Gep2->setOperand(NumOperands - 1, Induction);
+        Gep2->setOperand(NumOperands - 1, LastIndex);
         Ptr = Builder.Insert(Gep2);
         Ptr = Builder.CreateBitCast(Ptr, RetTy->getPointerTo());
         LI = Builder.CreateLoad(Ptr);
diff --git a/test/Transforms/LoopVectorize/induction_plus.ll b/test/Transforms/LoopVectorize/induction_plus.ll
new file mode 100644
index 0000000000..bd90113e52
--- /dev/null
+++ b/test/Transforms/LoopVectorize/induction_plus.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -loop-vectorize -instcombine -S | 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"
+
+@array = common global [1024 x i32] zeroinitializer, align 16
+
+;CHECK: @array_at_plus_one
+;CHECK: add <4 x i64>
+;CHECK: trunc <4 x i64>
+;CHECK: add i64 %index, 12
+;CHECK: ret i32
+define i32 @array_at_plus_one(i32 %n) nounwind uwtable ssp {
+  %1 = icmp sgt i32 %n, 0
+  br i1 %1, label %.lr.ph, label %._crit_edge
+
+.lr.ph:                                           ; preds = %0, %.lr.ph
+  %indvars.iv = phi i64 [ %indvars.iv.next, %.lr.ph ], [ 0, %0 ]
+  %2 = add nsw i64 %indvars.iv, 12
+  %3 = getelementptr inbounds [1024 x i32]* @array, i64 0, i64 %2
+  %4 = trunc i64 %indvars.iv to i32
+  store i32 %4, i32* %3, align 4
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %._crit_edge, label %.lr.ph
+
+._crit_edge:                                      ; preds = %.lr.ph, %0
+  ret i32 undef
+}