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SLPVectorizer: Fix stale for Value pointer array

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We are slicing an array of Value pointers and process those slices in a loop.
The problem is that we might invalidate a later slice by vectorizing a former
slice.

Use a WeakVH to track the pointer. If the pointer is deleted or RAUW'ed we can
tell.

The test case will only fail when running with libgmalloc.

radar://15498655

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195162 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2013-11-19 22:20:20 +00:00
parent 413f7bea8d
commit 4bc2e3a32d
2 changed files with 63 additions and 0 deletions
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30
lib/Transforms/Vectorize/SLPVectorizer.cpp
View File

@ -1833,6 +1833,21 @@ private:
StoreListMap StoreRefs;
};
/// \brief Check that the Values in the slice in VL array are still existant in
/// the WeakVH array.
/// Vectorization of part of the VL array may cause later values in the VL array
/// to become invalid. We track when this has happened in the WeakVH array.
static bool hasValueBeenRAUWed(ArrayRef<Value *> &VL,
SmallVectorImpl<WeakVH> &VH,
unsigned SliceBegin,
unsigned SliceSize) {
for (unsigned i = SliceBegin; i < SliceBegin + SliceSize; ++i)
if (VH[i] != VL[i])
return true;
return false;
}
bool SLPVectorizer::vectorizeStoreChain(ArrayRef<Value *> Chain,
int CostThreshold, BoUpSLP &R) {
unsigned ChainLen = Chain.size();
@ -1845,11 +1860,19 @@ bool SLPVectorizer::vectorizeStoreChain(ArrayRef<Value *> Chain,
if (!isPowerOf2_32(Sz) || VF < 2)
return false;
// Keep track of values that were delete by vectorizing in the loop below.
SmallVector<WeakVH, 8> TrackValues(Chain.begin(), Chain.end());
bool Changed = false;
// Look for profitable vectorizable trees at all offsets, starting at zero.
for (unsigned i = 0, e = ChainLen; i < e; ++i) {
if (i + VF > e)
break;
// Check that a previous iteration of this loop did not delete the Value.
if (hasValueBeenRAUWed(Chain, TrackValues, i, VF))
continue;
DEBUG(dbgs() << "SLP: Analyzing " << VF << " stores at offset " << i
<< "\n");
ArrayRef<Value *> Operands = Chain.slice(i, VF);
@ -1990,6 +2013,9 @@ bool SLPVectorizer::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R) {
bool Changed = false;
// Keep track of values that were delete by vectorizing in the loop below.
SmallVector<WeakVH, 8> TrackValues(VL.begin(), VL.end());
for (unsigned i = 0, e = VL.size(); i < e; ++i) {
unsigned OpsWidth = 0;
@ -2001,6 +2027,10 @@ bool SLPVectorizer::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R) {
if (!isPowerOf2_32(OpsWidth) || OpsWidth < 2)
break;
// Check that a previous iteration of this loop did not delete the Value.
if (hasValueBeenRAUWed(VL, TrackValues, i, OpsWidth))
continue;
DEBUG(dbgs() << "SLP: Analyzing " << OpsWidth << " operations "
<< "\n");
ArrayRef<Value *> Ops = VL.slice(i, OpsWidth);

33
test/Transforms/LoopVectorize/X86/rauw-bug.ll Normal file
View File

@ -0,0 +1,33 @@
; RUN: opt -slp-vectorizer -S %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-n32:64-S128"
target triple = "x86_64-apple-macosx"
; This test used to fail under libgmalloc. Because we would try to access a
; pointer that was already deleted.
;
; llvm-lit -v --param use_gmalloc=1 --param
; gmalloc_path=/usr/lib/libgmalloc.dylib
; test/Transforms/LoopVectorize/X86/rauw-bug.ll
;
; radar://15498655
; CHECK: reduced
define void @reduced() {
entry:
br i1 undef, label %while.body, label %while.cond63.preheader.while.end76_crit_edge
while.cond63.preheader.while.end76_crit_edge:
ret void
while.body:
%d2_fx.015 = phi double [ %sub52, %while.body ], [ undef, %entry ]
%d2_fy.014 = phi double [ %sub58, %while.body ], [ undef, %entry ]
%d3_fy.013 = phi double [ %div56, %while.body ], [ undef, %entry ]
%d3_fx.012 = phi double [ %div50, %while.body ], [ undef, %entry ]
%div50 = fmul double %d3_fx.012, 1.250000e-01
%sub52 = fsub double 0.000000e+00, %div50
%div56 = fmul double %d3_fy.013, 1.250000e-01
%sub58 = fsub double 0.000000e+00, %div56
br label %while.body
}