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[DependenceAnalysis] Allow subscripts of different types

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Summary:
Several places in DependenceAnalysis assumes both SCEVs in a subscript pair
share the same integer type. For instance, isKnownPredicate calls
SE->getMinusSCEV(X, Y) which asserts X and Y share the same type. However,
DependenceAnalysis fails to ensure this assumption when producing a subscript
pair, causing tests such as NonCanonicalizedSubscript to crash. With this
patch, DependenceAnalysis runs unifySubscriptType before producing any
subscript pair, ensuring the assumption.

Test Plan:
Added NonCanonicalizedSubscript.ll on which DependenceAnalysis before the fix
crashed because subscripts have different types.

Reviewers: spop, sebpop, jingyue

Reviewed By: jingyue

Subscribers: eliben, meheff, llvm-commits

Differential Revision: http://reviews.llvm.org/D6289

llvm-svn: 222100
This commit is contained in:
Jingyue Wu 2014-11-16 16:52:44 +00:00
parent eb88940e3d
commit 230717d66d
3 changed files with 74 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/llvm/Analysis/DependenceAnalysis.h
View File

@ -523,6 +523,12 @@ namespace llvm {
/// in LoopNest.
bool isLoopInvariant(const SCEV *Expression, const Loop *LoopNest) const;
/// Makes sure both subscripts (i.e. Pair->Src and Pair->Dst) share the same
/// integer type by sign-extending one of them when necessary.
/// Sign-extending a subscript is safe because getelementptr assumes the
/// array subscripts are signed.
void unifySubscriptType(Subscript *Pair);
/// removeMatchingExtensions - Examines a subscript pair.
/// If the source and destination are identically sign (or zero)
/// extended, it strips off the extension in an effort to
@ -911,7 +917,7 @@ namespace llvm {
bool tryDelinearize(const SCEV *SrcSCEV, const SCEV *DstSCEV,
SmallVectorImpl<Subscript> &Pair,
const SCEV *ElementSize) const;
const SCEV *ElementSize);
public:
static char ID; // Class identification, replacement for typeinfo

31
lib/Analysis/DependenceAnalysis.cpp
View File

@ -781,6 +781,25 @@ void DependenceAnalysis::collectCommonLoops(const SCEV *Expression,
}
}
void DependenceAnalysis::unifySubscriptType(Subscript *Pair) {
const SCEV *Src = Pair->Src;
const SCEV *Dst = Pair->Dst;
IntegerType *SrcTy = dyn_cast<IntegerType>(Src->getType());
IntegerType *DstTy = dyn_cast<IntegerType>(Dst->getType());
if (SrcTy == nullptr || DstTy == nullptr) {
assert(SrcTy == DstTy && "This function only unify integer types and "
"expect Src and Dst share the same type "
"otherwise.");
return;
}
if (SrcTy->getBitWidth() > DstTy->getBitWidth()) {
// Sign-extend Dst to typeof(Src) if typeof(Src) is wider than typeof(Dst).
Pair->Dst = SE->getSignExtendExpr(Dst, SrcTy);
} else if (SrcTy->getBitWidth() < DstTy->getBitWidth()) {
// Sign-extend Src to typeof(Dst) if typeof(Dst) is wider than typeof(Src).
Pair->Src = SE->getSignExtendExpr(Src, DstTy);
}
}
// removeMatchingExtensions - Examines a subscript pair.
// If the source and destination are identically sign (or zero)
@ -793,9 +812,11 @@ void DependenceAnalysis::removeMatchingExtensions(Subscript *Pair) {
(isa<SCEVSignExtendExpr>(Src) && isa<SCEVSignExtendExpr>(Dst))) {
const SCEVCastExpr *SrcCast = cast<SCEVCastExpr>(Src);
const SCEVCastExpr *DstCast = cast<SCEVCastExpr>(Dst);
if (SrcCast->getType() == DstCast->getType()) {
Pair->Src = SrcCast->getOperand();
Pair->Dst = DstCast->getOperand();
const SCEV *SrcCastOp = SrcCast->getOperand();
const SCEV *DstCastOp = DstCast->getOperand();
if (SrcCastOp->getType() == DstCastOp->getType()) {
Pair->Src = SrcCastOp;
Pair->Dst = DstCastOp;
}
}
}
@ -3178,7 +3199,7 @@ void DependenceAnalysis::updateDirection(Dependence::DVEntry &Level,
bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
const SCEV *DstSCEV,
SmallVectorImpl<Subscript> &Pair,
const SCEV *ElementSize) const {
const SCEV *ElementSize) {
const SCEVUnknown *SrcBase =
dyn_cast<SCEVUnknown>(SE->getPointerBase(SrcSCEV));
const SCEVUnknown *DstBase =
@ -3233,6 +3254,7 @@ bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
for (int i = 0; i < size; ++i) {
Pair[i].Src = SrcSubscripts[i];
Pair[i].Dst = DstSubscripts[i];
unifySubscriptType(&Pair[i]);
// FIXME: we should record the bounds SrcSizes[i] and DstSizes[i] that the
// delinearization has found, and add these constraints to the dependence
@ -3341,6 +3363,7 @@ DependenceAnalysis::depends(Instruction *Src, Instruction *Dst,
++SrcIdx, ++DstIdx, ++P) {
Pair[P].Src = SE->getSCEV(*SrcIdx);
Pair[P].Dst = SE->getSCEV(*DstIdx);
unifySubscriptType(&Pair[P]);
}
}
else {

40
test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll Normal file
View File

@ -0,0 +1,40 @@
; RUN: opt < %s -analyze -basicaa -da -da-delinearize=false | FileCheck %s
; RUN: opt < %s -analyze -basicaa -da -da-delinearize | FileCheck %s -check-prefix=DELIN
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-macosx10.6.0"
; for (int i = 0; i < 100; ++i) {
; int t0 = a[i][i];
; int t1 = t0 + 1;
; a[i][5] = t1;
; }
; The subscript 5 in a[i][5] is deliberately an i32, mismatching the types of
; other subscript. DependenceAnalysis before the fix crashed due to this
; mismatch.
define void @i32_subscript([100 x [100 x i32]]* %a, i32* %b) {
; CHECK-LABEL: 'Dependence Analysis' for function 'i32_subscript'
; DELIN-LABEL: 'Dependence Analysis' for function 'i32_subscript'
entry:
br label %for.body
for.body:
; CHECK: da analyze - none!
; CHECK: da analyze - anti [=|<]!
; CHECK: da analyze - none!
; DELIN: da analyze - none!
; DELIN: da analyze - anti [=|<]!
; DELIN: da analyze - none!
%i = phi i64 [ 0, %entry ], [ %i.inc, %for.body ]
%a.addr = getelementptr [100 x [100 x i32]]* %a, i64 0, i64 %i, i64 %i
%a.addr.2 = getelementptr [100 x [100 x i32]]* %a, i64 0, i64 %i, i32 5
%0 = load i32* %a.addr, align 4
%1 = add i32 %0, 1
store i32 %1, i32* %a.addr.2, align 4
%i.inc = add nsw i64 %i, 1
%exitcond = icmp ne i64 %i.inc, 100
br i1 %exitcond, label %for.body, label %for.end
for.end:
ret void
}