[llvm] r272335 - [CFLAA] Handle global/arg attrs more sanely.
George Burgess IV via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 9 16:15:05 PDT 2016
Author: gbiv
Date: Thu Jun 9 18:15:04 2016
New Revision: 272335
URL: http://llvm.org/viewvc/llvm-project?rev=272335&view=rev
Log:
[CFLAA] Handle global/arg attrs more sanely.
Prior to this patch, we used argument/global stratified attributes in
order to note that a value could have come from either dereferencing a
global/arg, or from the assignment from a global/arg.
Now, AttrUnknown is placed on sets when we see a dereference, instead of
the global/arg attributes. This allows us to be more aggressive in the
future when we see global/arg attributes without AttrUnknown.
Patch by Jia Chen.
Differential Revision: http://reviews.llvm.org/D21110
Modified:
llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp
llvm/trunk/lib/Analysis/StratifiedSets.h
llvm/trunk/test/Analysis/CFLAliasAnalysis/attr-escape.ll
Modified: llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp?rev=272335&r1=272334&r2=272335&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp Thu Jun 9 18:15:04 2016
@@ -657,6 +657,10 @@ typedef DenseMap<Value *, GraphT::Node>
/// as globals or arguments
static bool isGlobalOrArgAttr(StratifiedAttrs Attr);
+/// Given a StratifiedAttrs, returns true if the corresponding values come from
+/// an unknown source (such as opaque memory or an integer cast)
+static bool isUnknownAttr(StratifiedAttrs Attr);
+
/// Given an argument number, returns the appropriate StratifiedAttr to set.
static StratifiedAttr argNumberToAttr(unsigned ArgNum);
@@ -750,6 +754,10 @@ static bool isGlobalOrArgAttr(Stratified
return Attr.reset(AttrEscapedIndex).reset(AttrUnknownIndex).any();
}
+static bool isUnknownAttr(StratifiedAttrs Attr) {
+ return Attr.test(AttrUnknownIndex);
+}
+
static Optional<StratifiedAttr> valueToAttr(Value *Val) {
if (isa<GlobalValue>(Val))
return AttrGlobal;
@@ -955,6 +963,7 @@ CFLAAResult::FunctionInfo CFLAAResult::b
StratifiedSetsBuilder<Value *> Builder;
SmallVector<GraphT::Node, 16> Worklist;
+ SmallPtrSet<Value *, 16> Globals;
for (auto &Pair : Map) {
Worklist.clear();
@@ -968,9 +977,8 @@ CFLAAResult::FunctionInfo CFLAAResult::b
if (canSkipAddingToSets(CurValue))
continue;
- Optional<StratifiedAttr> MaybeCurAttr = valueToAttr(CurValue);
- if (MaybeCurAttr)
- Builder.noteAttributes(CurValue, *MaybeCurAttr);
+ if (isa<GlobalValue>(CurValue))
+ Globals.insert(CurValue);
for (const auto &EdgeTuple : Graph.edgesFor(Node)) {
auto Weight = std::get<0>(EdgeTuple);
@@ -980,6 +988,8 @@ CFLAAResult::FunctionInfo CFLAAResult::b
if (canSkipAddingToSets(OtherValue))
continue;
+ if (isa<GlobalValue>(OtherValue))
+ Globals.insert(OtherValue);
bool Added;
switch (directionOfEdgeType(Label)) {
@@ -995,10 +1005,6 @@ CFLAAResult::FunctionInfo CFLAAResult::b
}
auto Aliasing = Weight.second;
- if (MaybeCurAttr)
- Aliasing |= *MaybeCurAttr;
- if (auto MaybeOtherAttr = valueToAttr(OtherValue))
- Aliasing |= *MaybeOtherAttr;
Builder.noteAttributes(CurValue, Aliasing);
Builder.noteAttributes(OtherValue, Aliasing);
@@ -1008,18 +1014,21 @@ CFLAAResult::FunctionInfo CFLAAResult::b
}
}
- // There are times when we end up with parameters not in our graph (i.e. if
- // it's only used as the condition of a branch). Other bits of code depend on
- // things that were present during construction being present in the graph.
- // So, we add all present arguments here.
- for (auto &Arg : Fn->args()) {
- if (!Builder.add(&Arg))
- continue;
+ // Special handling for globals and arguments
+ auto ProcessGlobalOrArgValue = [&Builder](Value &Val) {
+ Builder.add(&Val);
+ auto Attr = valueToAttr(&Val);
+ if (Attr.hasValue()) {
+ Builder.noteAttributes(&Val, *Attr);
+ // TODO: do we need to filter out non-pointer values here?
+ Builder.addAttributesBelow(&Val, AttrUnknown);
+ }
+ };
- auto Attr = valueToAttr(&Arg);
- if (Attr.hasValue())
- Builder.noteAttributes(&Arg, *Attr);
- }
+ for (auto &Arg : Fn->args())
+ ProcessGlobalOrArgValue(Arg);
+ for (auto *Global : Globals)
+ ProcessGlobalOrArgValue(*Global);
return FunctionInfo(Builder.build(), std::move(ReturnedValues));
}
@@ -1104,13 +1113,13 @@ AliasResult CFLAAResult::query(const Mem
// bit more interesting. We follow three general rules described below:
// - Non-local values may alias each other
// - AttrNone values do not alias any non-local values
- // - AttrEscaped values do not alias globals/arguments, but they may alias
+ // - AttrEscaped do not alias globals/arguments, but they may alias
// AttrUnknown values
if (SetA.Index == SetB.Index)
return MayAlias;
if (AttrsA.none() || AttrsB.none())
return NoAlias;
- if (AttrsA.test(AttrUnknownIndex) || AttrsB.test(AttrUnknownIndex))
+ if (isUnknownAttr(AttrsA) || isUnknownAttr(AttrsB))
return MayAlias;
if (isGlobalOrArgAttr(AttrsA) && isGlobalOrArgAttr(AttrsB))
return MayAlias;
Modified: llvm/trunk/lib/Analysis/StratifiedSets.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/StratifiedSets.h?rev=272335&r1=272334&r2=272335&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/StratifiedSets.h (original)
+++ llvm/trunk/lib/Analysis/StratifiedSets.h Thu Jun 9 18:15:04 2016
@@ -395,6 +395,17 @@ public:
return addAtMerging(ToAdd, Below);
}
+ /// \brief Set the StratifiedAttrs of the set below "Main". If there is no set
+ /// below "Main", create one for it.
+ void addAttributesBelow(const T &Main, StratifiedAttrs Attr) {
+ assert(has(Main));
+ auto Index = *indexOf(Main);
+ auto Link = linksAt(Index);
+
+ auto BelowIndex = Link.hasBelow() ? Link.getBelow() : addLinkBelow(Index);
+ linksAt(BelowIndex).setAttrs(Attr);
+ }
+
bool addWith(const T &Main, const T &ToAdd) {
assert(has(Main));
auto MainIndex = *indexOf(Main);
Modified: llvm/trunk/test/Analysis/CFLAliasAnalysis/attr-escape.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/CFLAliasAnalysis/attr-escape.ll?rev=272335&r1=272334&r2=272335&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/CFLAliasAnalysis/attr-escape.ll (original)
+++ llvm/trunk/test/Analysis/CFLAliasAnalysis/attr-escape.ll Thu Jun 9 18:15:04 2016
@@ -3,16 +3,30 @@
; RUN: opt < %s -disable-basicaa -cfl-aa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
; RUN: opt < %s -aa-pipeline=cfl-aa -passes=aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
-; CHECK: Function: escape_ptrtoint
-; CHECK: NoAlias: i32* %a, i32* %x
-; CHECK: NoAlias: i32* %b, i32* %x
+; CHECK-LABEL: Function: test_local
; CHECK: NoAlias: i32* %a, i32* %b
; CHECK: MayAlias: i32* %a, i32* %aAlias
; CHECK: NoAlias: i32* %aAlias, i32* %b
-define void @escape_ptrtoint(i32* %x) {
+define void @test_local() {
%a = alloca i32, align 4
%b = alloca i32, align 4
%aint = ptrtoint i32* %a to i64
%aAlias = inttoptr i64 %aint to i32*
ret void
}
+
+; CHECK-LABEL: Function: test_global_param
+; CHECK: NoAlias: i32* %a, i32** %x
+; CHECK: MayAlias: i32* %a, i32* %xload
+; CHECK: MayAlias: i32* %a, i32* %gload
+; CHECK: MayAlias: i32* %gload, i32* %xload
+; CHECK: MayAlias: i32** %x, i32** @ext_global
+; CHECK: NoAlias: i32* %a, i32** @ext_global
+ at ext_global = external global i32*
+define void @test_global_param(i32** %x) {
+ %a = alloca i32, align 4
+ %aint = ptrtoint i32* %a to i64
+ %xload = load i32*, i32** %x
+ %gload = load i32*, i32** @ext_global
+ ret void
+}
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