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[LoopAccesses] Add -analyze support 

The LoopInfo in combination with depth_first is used to enumerate the
loops.

Right now -analyze is not yet complete.  It only prints the result of
the analysis, the report and the run-time checks.  Printing the unsafe
depedences will require a bit more reshuffling which I'd like to do in a
follow-on to this patchset.  Unsafe dependences are currently checked
via -debug-only=loop-accesses in the new test.

This is part of the patchset that converts LoopAccessAnalysis into an
actual analysis pass.

llvm-svn: 229633
This commit is contained in:
Adam Nemet 2015-02-18 03:44:30 +00:00
parent d7350dbb85
commit 75bc2d111f
4 changed files with 184 additions and 0 deletions
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12
llvm/include/llvm/Analysis/LoopAccessAnalysis.h
View File

@ -120,10 +120,16 @@ public:
void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr,
unsigned DepSetId, unsigned ASId, ValueToValueMap &Strides);
/// \brief No run-time memory checking is necessary.
bool empty() const { return Pointers.empty(); }
/// \brief Decide whether we need to issue a run-time check for pointer at
/// index \p I and \p J to prove their independence.
bool needsChecking(unsigned I, unsigned J) const;
/// \brief Print the list run-time memory checks necessary.
void print(raw_ostream &OS, unsigned Depth = 0) const;
/// This flag indicates if we need to add the runtime check.
bool Need;
/// Holds the pointers that we need to check.
@ -174,6 +180,9 @@ public:
/// couldn't analyze the loop.
Optional<LoopAccessReport> &getReport() { return Report; }
/// \brief Print the information about the memory accesses in the loop.
void print(raw_ostream &OS, unsigned Depth = 0) const;
/// \brief Used to ensure that if the analysis was run with speculating the
/// value of symbolic strides, the client queries it with the same assumption.
/// Only used in DEBUG build but we don't want NDEBUG-depedent ABI.
@ -256,6 +265,9 @@ public:
LoopAccessInfoMap.clear();
}
/// \brief Print the result of the analysis when invoked with -analyze.
void print(raw_ostream &OS, const Module *M = nullptr) const override;
private:
/// \brief The cache.
DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;

51
llvm/lib/Analysis/LoopAccessAnalysis.cpp
View File

@ -110,6 +110,23 @@ bool LoopAccessInfo::RuntimePointerCheck::needsChecking(unsigned I,
return true;
}
void LoopAccessInfo::RuntimePointerCheck::print(raw_ostream &OS,
unsigned Depth) const {
unsigned NumPointers = Pointers.size();
if (NumPointers == 0)
return;
OS.indent(Depth) << "Run-time memory checks:\n";
unsigned N = 0;
for (unsigned I = 0; I < NumPointers; ++I)
for (unsigned J = I + 1; J < NumPointers; ++J)
if (needsChecking(I, J)) {
OS.indent(Depth) << N++ << ":\n";
OS.indent(Depth + 2) << *Pointers[I] << "\n";
OS.indent(Depth + 2) << *Pointers[J] << "\n";
}
}
namespace {
/// \brief Analyses memory accesses in a loop.
///
@ -1266,6 +1283,24 @@ LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
analyzeLoop(Strides);
}
void LoopAccessInfo::print(raw_ostream &OS, unsigned Depth) const {
if (CanVecMem) {
if (PtrRtCheck.empty())
OS.indent(Depth) << "Memory dependences are safe\n";
else
OS.indent(Depth) << "Memory dependences are safe with run-time checks\n";
}
if (Report)
OS.indent(Depth) << "Report: " << Report->str() << "\n";
// FIXME: Print unsafe dependences
// List the pair of accesses need run-time checks to prove independence.
PtrRtCheck.print(OS, Depth);
OS << "\n";
}
LoopAccessInfo &LoopAccessAnalysis::getInfo(Loop *L, ValueToValueMap &Strides) {
auto &LAI = LoopAccessInfoMap[L];
@ -1283,6 +1318,20 @@ LoopAccessInfo &LoopAccessAnalysis::getInfo(Loop *L, ValueToValueMap &Strides) {
return *LAI.get();
}
void LoopAccessAnalysis::print(raw_ostream &OS, const Module *M) const {
LoopAccessAnalysis &LAA = *const_cast<LoopAccessAnalysis *>(this);
LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
ValueToValueMap NoSymbolicStrides;
for (Loop *TopLevelLoop : *LI)
for (Loop *L : depth_first(TopLevelLoop)) {
OS.indent(2) << L->getHeader()->getName() << ":\n";
auto &LAI = LAA.getInfo(L, NoSymbolicStrides);
LAI.print(OS, 4);
}
}
bool LoopAccessAnalysis::runOnFunction(Function &F) {
SE = &getAnalysis<ScalarEvolution>();
DL = F.getParent()->getDataLayout();
@ -1298,6 +1347,7 @@ void LoopAccessAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<ScalarEvolution>();
AU.addRequired<AliasAnalysis>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.setPreservesAll();
}
@ -1310,6 +1360,7 @@ INITIALIZE_PASS_BEGIN(LoopAccessAnalysis, LAA_NAME, laa_name, false, true)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(LoopAccessAnalysis, LAA_NAME, laa_name, false, true)
namespace llvm {

60
llvm/test/Analysis/LoopAccessAnalysis/unsafe-and-rt-checks-no-dbg.ll Normal file
View File

@ -0,0 +1,60 @@
; RUN: opt -loop-accesses -analyze < %s | FileCheck %s
; FIXME: This is the non-debug version of unsafe-and-rt-checks.ll not
; requiring "asserts". Once we can check memory dependences without -debug,
; we should remove this test.
; Analyze this loop:
; for (i = 0; i < n; i++)
; A[i + 1] = A[i] * B[i] * C[i];
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.10.0"
; CHECK: Report: unsafe dependent memory operations in loop
; CHECK: Run-time memory checks:
; CHECK-NEXT: 0:
; CHECK-NEXT: %arrayidxA_plus_2 = getelementptr inbounds i16* %a, i64 %add
; CHECK-NEXT: %arrayidxB = getelementptr inbounds i16* %b, i64 %storemerge3
; CHECK-NEXT: 1:
; CHECK-NEXT: %arrayidxA_plus_2 = getelementptr inbounds i16* %a, i64 %add
; CHECK-NEXT: %arrayidxC = getelementptr inbounds i16* %c, i64 %storemerge3
@n = global i32 20, align 4
@B = common global i16* null, align 8
@A = common global i16* null, align 8
@C = common global i16* null, align 8
define void @f() {
entry:
%a = load i16** @A, align 8
%b = load i16** @B, align 8
%c = load i16** @C, align 8
br label %for.body
for.body: ; preds = %for.body, %entry
%storemerge3 = phi i64 [ 0, %entry ], [ %add, %for.body ]
%arrayidxA = getelementptr inbounds i16* %a, i64 %storemerge3
%loadA = load i16* %arrayidxA, align 2
%arrayidxB = getelementptr inbounds i16* %b, i64 %storemerge3
%loadB = load i16* %arrayidxB, align 2
%arrayidxC = getelementptr inbounds i16* %c, i64 %storemerge3
%loadC = load i16* %arrayidxC, align 2
%mul = mul i16 %loadB, %loadA
%mul1 = mul i16 %mul, %loadC
%add = add nuw nsw i64 %storemerge3, 1
%arrayidxA_plus_2 = getelementptr inbounds i16* %a, i64 %add
store i16 %mul1, i16* %arrayidxA_plus_2, align 2
%exitcond = icmp eq i64 %add, 20
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body
ret void
}

61
llvm/test/Analysis/LoopAccessAnalysis/unsafe-and-rt-checks.ll Normal file
View File

@ -0,0 +1,61 @@
; RUN: opt -loop-accesses -analyze < %s | FileCheck %s
; RUN: opt -loop-accesses -analyze -debug-only=loop-accesses < %s 2>&1 | FileCheck %s --check-prefix=DEBUG
; REQUIRES: asserts
; Analyze this loop:
; for (i = 0; i < n; i++)
; A[i + 1] = A[i] * B[i] * C[i];
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.10.0"
; CHECK: Report: unsafe dependent memory operations in loop
; DEBUG: LAA: Distance for %loadA = load i16* %arrayidxA, align 2 to store i16 %mul1, i16* %arrayidxA_plus_2, align 2: 2
; DEBUG-NEXT: LAA: Failure because of Positive distance 2
; CHECK: Run-time memory checks:
; CHECK-NEXT: 0:
; CHECK-NEXT: %arrayidxA_plus_2 = getelementptr inbounds i16* %a, i64 %add
; CHECK-NEXT: %arrayidxB = getelementptr inbounds i16* %b, i64 %storemerge3
; CHECK-NEXT: 1:
; CHECK-NEXT: %arrayidxA_plus_2 = getelementptr inbounds i16* %a, i64 %add
; CHECK-NEXT: %arrayidxC = getelementptr inbounds i16* %c, i64 %storemerge3
@n = global i32 20, align 4
@B = common global i16* null, align 8
@A = common global i16* null, align 8
@C = common global i16* null, align 8
define void @f() {
entry:
%a = load i16** @A, align 8
%b = load i16** @B, align 8
%c = load i16** @C, align 8
br label %for.body
for.body: ; preds = %for.body, %entry
%storemerge3 = phi i64 [ 0, %entry ], [ %add, %for.body ]
%arrayidxA = getelementptr inbounds i16* %a, i64 %storemerge3
%loadA = load i16* %arrayidxA, align 2
%arrayidxB = getelementptr inbounds i16* %b, i64 %storemerge3
%loadB = load i16* %arrayidxB, align 2
%arrayidxC = getelementptr inbounds i16* %c, i64 %storemerge3
%loadC = load i16* %arrayidxC, align 2
%mul = mul i16 %loadB, %loadA
%mul1 = mul i16 %mul, %loadC
%add = add nuw nsw i64 %storemerge3, 1
%arrayidxA_plus_2 = getelementptr inbounds i16* %a, i64 %add
store i16 %mul1, i16* %arrayidxA_plus_2, align 2
%exitcond = icmp eq i64 %add, 20
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body
ret void
}