[llvm] r182485 - LoopVectorize: Make Value pointers that could be RAUW'ed a VH

[Rafael Espíndola]

Hi Bill,

It would be really nice to pull this one to the 3.3 branch.

On 22 May 2013 12:54, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:
> Author: arnolds
> Date: Wed May 22 11:54:56 2013
> New Revision: 182485
>
> URL: http://llvm.org/viewvc/llvm-project?rev=182485&view=rev
> Log:
> 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.
>
> Added:
>     llvm/trunk/test/Transforms/LoopVectorize/value-ptr-bug.ll
> Modified:
>     llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
>
> Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=182485&r1=182484&r2=182485&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
> +++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Wed May 22 11:54:56 2013
> @@ -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 @@ public:
>
>      // 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 @@ public:
>      /// 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 @@ public:
>      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;
>    };
>
> Added: llvm/trunk/test/Transforms/LoopVectorize/value-ptr-bug.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/value-ptr-bug.ll?rev=182485&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/LoopVectorize/value-ptr-bug.ll (added)
> +++ llvm/trunk/test/Transforms/LoopVectorize/value-ptr-bug.ll Wed May 22 11:54:56 2013
> @@ -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
> +}
>
>
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