LoopVectorize: Make Value pointers that could be RAUW'ed a VH

The Value pointers we store in the induction variable list can be RAUW'ed by a
call to SCEVExpander::expandCodeFor, use a TrackingVH instead. Do the same thing
in some other places where we store pointers that could potentially be RAUW'ed.

Fixes PR16073.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182485 91177308-0d34-0410-b5e6-96231b3b80d8

Author: aschwaighofer

lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -80,6 +80,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/PatternMatch.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/ValueHandle.h"
 #include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
@@ -458,7 +459,7 @@ class LoopVectorizationLegality {
 
     // The starting value of the reduction.
     // It does not have to be zero!
-    Value *StartValue;
+    TrackingVH<Value> StartValue;
     // The instruction who's value is used outside the loop.
     Instruction *LoopExitInstr;
     // The kind of the reduction.
@@ -503,7 +504,7 @@ class LoopVectorizationLegality {
     /// This flag indicates if we need to add the runtime check.
     bool Need;
     /// Holds the pointers that we need to check.
-    SmallVector<Value*, 2> Pointers;
+    SmallVector<TrackingVH<Value>, 2> Pointers;
     /// Holds the pointer value at the beginning of the loop.
     SmallVector<const SCEV*, 2> Starts;
     /// Holds the pointer value at the end of the loop.
@@ -517,7 +518,7 @@ class LoopVectorizationLegality {
     InductionInfo(Value *Start, InductionKind K) : StartValue(Start), IK(K) {}
     InductionInfo() : StartValue(0), IK(IK_NoInduction) {}
     /// Start value.
-    Value *StartValue;
+    TrackingVH<Value> StartValue;
     /// Induction kind.
     InductionKind IK;
   };

test/Transforms/LoopVectorize/value-ptr-bug.ll

@@ -0,0 +1,50 @@
+; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-unroll=1 -dce -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"
+
+; PR16073
+
+; Because we were caching value pointers accross a function call that could RAUW
+; we would generate an undefined value store below:
+; SCEVExpander::expandCodeFor would change a value (the start value of an
+; induction) that we cached in the induction variable list.
+
+; CHECK: test_vh
+; CHECK-NOT: store <4 x i8> undef
+
+define void @test_vh(i32* %ptr265, i32* %ptr266, i32 %sub267) {
+entry:
+  br label %loop
+
+loop:
+  %inc = phi i32 [ %sub267, %entry ], [ %add, %loop]
+  %ext.inc = sext i32 %inc to i64
+  %add.ptr265 = getelementptr inbounds i32* %ptr265, i64 %ext.inc
+  %add.ptr266 = getelementptr inbounds i32* %ptr266, i64 %ext.inc
+  %add = add i32 %inc, 9
+  %cmp = icmp slt i32 %add, 140
+  br i1 %cmp, label %block1, label %loop
+
+block1:
+  %sub267.lcssa = phi i32 [ %add, %loop ]
+  %add.ptr266.lcssa = phi i32* [ %add.ptr266, %loop ]
+  %add.ptr265.lcssa = phi i32* [ %add.ptr265, %loop ]
+  %tmp29 = bitcast i32* %add.ptr265.lcssa to i8*
+  %tmp30 = bitcast i32* %add.ptr266.lcssa to i8*
+  br label %do.body272
+
+do.body272:
+  %row_width.5 = phi i32 [ %sub267.lcssa, %block1 ], [ %dec, %do.body272 ]
+  %sp.4 = phi i8* [ %tmp30, %block1 ], [ %incdec.ptr273, %do.body272 ]
+  %dp.addr.4 = phi i8* [ %tmp29, %block1 ], [ %incdec.ptr274, %do.body272 ]
+  %incdec.ptr273 = getelementptr inbounds i8* %sp.4, i64 1
+  %tmp31 = load i8* %sp.4, align 1
+  %incdec.ptr274 = getelementptr inbounds i8* %dp.addr.4, i64 1
+  store i8 %tmp31, i8* %dp.addr.4, align 1
+  %dec = add i32 %row_width.5, -1
+  %cmp276 = icmp eq i32 %dec, 0
+  br i1 %cmp276, label %loop.exit, label %do.body272
+
+loop.exit:
+  ret void
+}