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Add argmemonly attribute. 

This change adds new attribute called "argmemonly". Function marked with this attribute can only access memory through it's argument pointers. This attribute directly corresponds to the "OnlyAccessesArgumentPointees" ModRef behaviour in alias analysis.

Differential Revision: http://reviews.llvm.org/D10398

llvm-svn: 241979
This commit is contained in:
Igor Laevsky 2015-07-11 10:30:36 +00:00
parent 15f5d97311
commit 39d662f7ba
17 changed files with 167 additions and 35 deletions
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8
llvm/docs/LangRef.rst
View File

@ -1326,6 +1326,14 @@ example:
On an argument, this attribute indicates that the function does not write
through this pointer argument, even though it may write to the memory that
the pointer points to.
``argmemonly``
This attribute indicates that the only memory accesses inside function are
loads and stores from objects pointed to by its pointer-typed arguments,
with arbitrary offsets. Or in other words, all memory operations in the
function can refer to memory only using pointers based on its function
arguments.
Note that ``argmemonly`` can be used together with ``readonly`` attribute
in order to specify that function reads only from its arguments.
``returns_twice``
This attribute indicates that this function can return twice. The C
``setjmp`` is an example of such a function. The compiler disables

3
llvm/include/llvm/Analysis/AliasAnalysis.h
View File

@ -211,6 +211,8 @@ public:
/// (if it has any) are non-volatile loads from objects pointed to by its
/// pointer-typed arguments, with arbitrary offsets.
///
/// This property corresponds to the LLVM IR 'argmemonly' attribute combined
/// with 'readonly' attribute.
/// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
OnlyReadsArgumentPointees = ArgumentPointees | Ref,
@ -218,6 +220,7 @@ public:
/// function (if it has any) are non-volatile loads and stores from objects
/// pointed to by its pointer-typed arguments, with arbitrary offsets.
///
/// This property corresponds to the LLVM IR 'argmemonly' attribute.
/// This property corresponds to the IntrReadWriteArgMem LLVM intrinsic flag.
OnlyAccessesArgumentPointees = ArgumentPointees | ModRef,

1
llvm/include/llvm/Bitcode/LLVMBitCodes.h
View File

@ -407,6 +407,7 @@ namespace bitc {
ATTR_KIND_DEREFERENCEABLE_OR_NULL = 42,
ATTR_KIND_CONVERGENT = 43,
ATTR_KIND_SAFESTACK = 44,
ATTR_KIND_ARGMEMONLY = 45
};
enum ComdatSelectionKindCodes {

2
llvm/include/llvm/IR/Attributes.h
View File

@ -98,6 +98,8 @@ public:
OptimizeNone, ///< Function must not be optimized.
ReadNone, ///< Function does not access memory
ReadOnly, ///< Function only reads from memory
ArgMemOnly, ///< Funciton can access memory only using pointers
///< based on its arguments.
Returned, ///< Return value is always equal to this argument
ReturnsTwice, ///< Function can return twice
SExt, ///< Sign extended before/after call

9
llvm/include/llvm/IR/CallSite.h
View File

@ -290,6 +290,15 @@ public:
CALLSITE_DELEGATE_SETTER(setOnlyReadsMemory());
}
/// @brief Determine if the call can access memmory only using pointers based
/// on its arguments.
bool onlyAccessesArgMemory() const {
CALLSITE_DELEGATE_GETTER(onlyAccessesArgMemory());
}
void setOnlyAccessesArgMemory() {
CALLSITE_DELEGATE_SETTER(setOnlyAccessesArgMemory());
}
/// @brief Determine if the call cannot return.
bool doesNotReturn() const {
CALLSITE_DELEGATE_GETTER(doesNotReturn());

10
llvm/include/llvm/IR/Function.h
View File

@ -293,6 +293,16 @@ public:
addFnAttr(Attribute::ReadOnly);
}
/// @brief Determine if the call can access memmory only using pointers based
/// on its arguments.
bool onlyAccessesArgMemory() const {
return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
Attribute::ArgMemOnly);
}
void setOnlyAccessesArgMemory() {
addFnAttr(Attribute::ArgMemOnly);
}
/// @brief Determine if the function cannot return.
bool doesNotReturn() const {
return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,

18
llvm/include/llvm/IR/Instructions.h
View File

@ -1595,6 +1595,15 @@ public:
addAttribute(AttributeSet::FunctionIndex, Attribute::ReadOnly);
}
/// @brief Determine if the call can access memmory only using pointers based
/// on its arguments.
bool onlyAccessesArgMemory() const {
return hasFnAttr(Attribute::ArgMemOnly);
}
void setOnlyAccessesArgMemory() {
addAttribute(AttributeSet::FunctionIndex, Attribute::ArgMemOnly);
}
/// \brief Determine if the call cannot return.
bool doesNotReturn() const { return hasFnAttr(Attribute::NoReturn); }
void setDoesNotReturn() {
@ -3364,6 +3373,15 @@ public:
addAttribute(AttributeSet::FunctionIndex, Attribute::ReadOnly);
}
/// @brief Determine if the call access memmory only using it's pointer
/// arguments.
bool onlyAccessesArgMemory() const {
return hasFnAttr(Attribute::ArgMemOnly);
}
void setOnlyAccessesArgMemory() {
addAttribute(AttributeSet::FunctionIndex, Attribute::ArgMemOnly);
}
/// \brief Determine if the call cannot return.
bool doesNotReturn() const { return hasFnAttr(Attribute::NoReturn); }
void setDoesNotReturn() {

6
llvm/lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -685,6 +685,9 @@ BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
if (CS.onlyReadsMemory())
Min = OnlyReadsMemory;
if (CS.onlyAccessesArgMemory())
Min = ModRefBehavior(Min & OnlyAccessesArgumentPointees);
// The AliasAnalysis base class has some smarts, lets use them.
return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
}
@ -710,6 +713,9 @@ BasicAliasAnalysis::getModRefBehavior(const Function *F) {
if (F->onlyReadsMemory())
Min = OnlyReadsMemory;
if (F->onlyAccessesArgMemory())
Min = ModRefBehavior(Min & OnlyAccessesArgumentPointees);
const TargetLibraryInfo &TLI =
getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
if (isMemsetPattern16(F, TLI))

1
llvm/lib/AsmParser/LLLexer.cpp
View File

@ -593,6 +593,7 @@ lltok::Kind LLLexer::LexIdentifier() {
KEYWORD(attributes);
KEYWORD(alwaysinline);
KEYWORD(argmemonly);
KEYWORD(builtin);
KEYWORD(byval);
KEYWORD(inalloca);

67
llvm/lib/AsmParser/LLParser.cpp
View File

@ -946,35 +946,42 @@ bool LLParser::ParseFnAttributeValuePairs(AttrBuilder &B,
B.addStackAlignmentAttr(Alignment);
continue;
}
case lltok::kw_alwaysinline: B.addAttribute(Attribute::AlwaysInline); break;
case lltok::kw_builtin: B.addAttribute(Attribute::Builtin); break;
case lltok::kw_cold: B.addAttribute(Attribute::Cold); break;
case lltok::kw_convergent: B.addAttribute(Attribute::Convergent); break;
case lltok::kw_inlinehint: B.addAttribute(Attribute::InlineHint); break;
case lltok::kw_jumptable: B.addAttribute(Attribute::JumpTable); break;
case lltok::kw_minsize: B.addAttribute(Attribute::MinSize); break;
case lltok::kw_naked: B.addAttribute(Attribute::Naked); break;
case lltok::kw_nobuiltin: B.addAttribute(Attribute::NoBuiltin); break;
case lltok::kw_noduplicate: B.addAttribute(Attribute::NoDuplicate); break;
case lltok::kw_noimplicitfloat: B.addAttribute(Attribute::NoImplicitFloat); break;
case lltok::kw_noinline: B.addAttribute(Attribute::NoInline); break;
case lltok::kw_nonlazybind: B.addAttribute(Attribute::NonLazyBind); break;
case lltok::kw_noredzone: B.addAttribute(Attribute::NoRedZone); break;
case lltok::kw_noreturn: B.addAttribute(Attribute::NoReturn); break;
case lltok::kw_nounwind: B.addAttribute(Attribute::NoUnwind); break;
case lltok::kw_optnone: B.addAttribute(Attribute::OptimizeNone); break;
case lltok::kw_optsize: B.addAttribute(Attribute::OptimizeForSize); break;
case lltok::kw_readnone: B.addAttribute(Attribute::ReadNone); break;
case lltok::kw_readonly: B.addAttribute(Attribute::ReadOnly); break;
case lltok::kw_returns_twice: B.addAttribute(Attribute::ReturnsTwice); break;
case lltok::kw_ssp: B.addAttribute(Attribute::StackProtect); break;
case lltok::kw_sspreq: B.addAttribute(Attribute::StackProtectReq); break;
case lltok::kw_sspstrong: B.addAttribute(Attribute::StackProtectStrong); break;
case lltok::kw_safestack: B.addAttribute(Attribute::SafeStack); break;
case lltok::kw_sanitize_address: B.addAttribute(Attribute::SanitizeAddress); break;
case lltok::kw_sanitize_thread: B.addAttribute(Attribute::SanitizeThread); break;
case lltok::kw_sanitize_memory: B.addAttribute(Attribute::SanitizeMemory); break;
case lltok::kw_uwtable: B.addAttribute(Attribute::UWTable); break;
case lltok::kw_alwaysinline: B.addAttribute(Attribute::AlwaysInline); break;
case lltok::kw_argmemonly: B.addAttribute(Attribute::ArgMemOnly); break;
case lltok::kw_builtin: B.addAttribute(Attribute::Builtin); break;
case lltok::kw_cold: B.addAttribute(Attribute::Cold); break;
case lltok::kw_convergent: B.addAttribute(Attribute::Convergent); break;
case lltok::kw_inlinehint: B.addAttribute(Attribute::InlineHint); break;
case lltok::kw_jumptable: B.addAttribute(Attribute::JumpTable); break;
case lltok::kw_minsize: B.addAttribute(Attribute::MinSize); break;
case lltok::kw_naked: B.addAttribute(Attribute::Naked); break;
case lltok::kw_nobuiltin: B.addAttribute(Attribute::NoBuiltin); break;
case lltok::kw_noduplicate: B.addAttribute(Attribute::NoDuplicate); break;
case lltok::kw_noimplicitfloat:
B.addAttribute(Attribute::NoImplicitFloat); break;
case lltok::kw_noinline: B.addAttribute(Attribute::NoInline); break;
case lltok::kw_nonlazybind: B.addAttribute(Attribute::NonLazyBind); break;
case lltok::kw_noredzone: B.addAttribute(Attribute::NoRedZone); break;
case lltok::kw_noreturn: B.addAttribute(Attribute::NoReturn); break;
case lltok::kw_nounwind: B.addAttribute(Attribute::NoUnwind); break;
case lltok::kw_optnone: B.addAttribute(Attribute::OptimizeNone); break;
case lltok::kw_optsize: B.addAttribute(Attribute::OptimizeForSize); break;
case lltok::kw_readnone: B.addAttribute(Attribute::ReadNone); break;
case lltok::kw_readonly: B.addAttribute(Attribute::ReadOnly); break;
case lltok::kw_returns_twice:
B.addAttribute(Attribute::ReturnsTwice); break;
case lltok::kw_ssp: B.addAttribute(Attribute::StackProtect); break;
case lltok::kw_sspreq: B.addAttribute(Attribute::StackProtectReq); break;
case lltok::kw_sspstrong:
B.addAttribute(Attribute::StackProtectStrong); break;
case lltok::kw_safestack: B.addAttribute(Attribute::SafeStack); break;
case lltok::kw_sanitize_address:
B.addAttribute(Attribute::SanitizeAddress); break;
case lltok::kw_sanitize_thread:
B.addAttribute(Attribute::SanitizeThread); break;
case lltok::kw_sanitize_memory:
B.addAttribute(Attribute::SanitizeMemory); break;
case lltok::kw_uwtable: B.addAttribute(Attribute::UWTable); break;
// Error handling.
case lltok::kw_inreg:
@ -1258,6 +1265,7 @@ bool LLParser::ParseOptionalParamAttrs(AttrBuilder &B) {
case lltok::kw_alignstack:
case lltok::kw_alwaysinline:
case lltok::kw_argmemonly:
case lltok::kw_builtin:
case lltok::kw_inlinehint:
case lltok::kw_jumptable:
@ -1334,6 +1342,7 @@ bool LLParser::ParseOptionalReturnAttrs(AttrBuilder &B) {
case lltok::kw_alignstack:
case lltok::kw_alwaysinline:
case lltok::kw_argmemonly:
case lltok::kw_builtin:
case lltok::kw_cold:
case lltok::kw_inlinehint:

1
llvm/lib/AsmParser/LLToken.h
View File

@ -100,6 +100,7 @@ namespace lltok {
// Attributes:
kw_attributes,
kw_alwaysinline,
kw_argmemonly,
kw_sanitize_address,
kw_builtin,
kw_byval,

2
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
View File

@ -1090,6 +1090,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
return Attribute::Alignment;
case bitc::ATTR_KIND_ALWAYS_INLINE:
return Attribute::AlwaysInline;
case bitc::ATTR_KIND_ARGMEMONLY:
return Attribute::ArgMemOnly;
case bitc::ATTR_KIND_BUILTIN:
return Attribute::Builtin;
case bitc::ATTR_KIND_BY_VAL:

2
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -162,6 +162,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
return bitc::ATTR_KIND_ALIGNMENT;
case Attribute::AlwaysInline:
return bitc::ATTR_KIND_ALWAYS_INLINE;
case Attribute::ArgMemOnly:
return bitc::ATTR_KIND_ARGMEMONLY;
case Attribute::Builtin:
return bitc::ATTR_KIND_BUILTIN;
case Attribute::ByVal:

8
llvm/lib/IR/Attributes.cpp
View File

@ -190,6 +190,8 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
return "sanitize_address";
if (hasAttribute(Attribute::AlwaysInline))
return "alwaysinline";
if (hasAttribute(Attribute::ArgMemOnly))
return "argmemonly";
if (hasAttribute(Attribute::Builtin))
return "builtin";
if (hasAttribute(Attribute::ByVal))
@ -447,6 +449,9 @@ uint64_t AttributeImpl::getAttrMask(Attribute::AttrKind Val) {
llvm_unreachable("dereferenceable_or_null attribute not supported in raw "
"format");
break;
case Attribute::ArgMemOnly:
llvm_unreachable("argmemonly attribute not supported in raw format");
break;
}
llvm_unreachable("Unsupported attribute type");
}
@ -1356,7 +1361,8 @@ AttrBuilder &AttrBuilder::addRawValue(uint64_t Val) {
for (Attribute::AttrKind I = Attribute::None; I != Attribute::EndAttrKinds;
I = Attribute::AttrKind(I + 1)) {
if (I == Attribute::Dereferenceable ||
I == Attribute::DereferenceableOrNull)
I == Attribute::DereferenceableOrNull ||
I == Attribute::ArgMemOnly)
continue;
if (uint64_t A = (Val & AttributeImpl::getAttrMask(I))) {
Attrs[I] = true;

8
llvm/lib/IR/Verifier.cpp
View File

@ -1273,7 +1273,8 @@ void Verifier::VerifyAttributeTypes(AttributeSet Attrs, unsigned Idx,
I->getKindAsEnum() == Attribute::Cold ||
I->getKindAsEnum() == Attribute::OptimizeNone ||
I->getKindAsEnum() == Attribute::JumpTable ||
I->getKindAsEnum() == Attribute::Convergent) {
I->getKindAsEnum() == Attribute::Convergent ||
I->getKindAsEnum() == Attribute::ArgMemOnly) {
if (!isFunction) {
CheckFailed("Attribute '" + I->getAsString() +
"' only applies to functions!", V);
@ -1531,8 +1532,9 @@ void Verifier::VerifyStatepoint(ImmutableCallSite CS) {
const Instruction &CI = *CS.getInstruction();
Assert(!CS.doesNotAccessMemory() && !CS.onlyReadsMemory(),
"gc.statepoint must read and write memory to preserve "
Assert(!CS.doesNotAccessMemory() && !CS.onlyReadsMemory() &&
!CS.onlyAccessesArgMemory(),
"gc.statepoint must read and write all memory to preserve "
"reordering restrictions required by safepoint semantics",
&CI);

45
llvm/test/Analysis/BasicAA/modref.ll
View File

@ -145,6 +145,51 @@ entry:
; CHECK: load i32, i32*
}
;; Check that aa correctly handles functions marked with argmemonly
;; attribute.
declare i32 @func_argmemonly(i32 * %P) argmemonly
;; Can not remove redundant load, function may write to it.
; CHECK-LABEL: @test8(
define i32 @test8(i32 *%P) {
%V1 = load i32, i32* %P
call i32 @func_argmemonly(i32* %P)
%V2 = load i32, i32* %P
%Diff = sub i32 %V1, %V2
ret i32 %Diff
; CHECK: load
; CHECK: load
; CHECK: sub
; CHECK: ret i32 %Diff
}
;; In this case load can be removed, function clobbers only %P2.
; CHECK-LABEL: @test9(
define i32 @test9(i32* %P, i32* noalias %P2) {
%V1 = load i32, i32* %P
call i32 @func_argmemonly(i32* %P2)
%V2 = load i32, i32* %P
%Diff = sub i32 %V1, %V2
ret i32 %Diff
; CHECK-NOT: load
; CHECK: ret i32 0
}
;; In this case load can *not* be removed. Function clobers only %P2 but it may
;; alias with %P.
; CHECK-LABEL: @test10(
define i32 @test10(i32* %P, i32* %P2) {
%V1 = load i32, i32* %P
call i32 @func_argmemonly(i32* %P2)
%V2 = load i32, i32* %P
%Diff = sub i32 %V1, %V2
ret i32 %Diff
; CHECK: load
; CHECK: load
; CHECK: sub
; CHECK: ret i32 %Diff
}
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) nounwind
declare void @llvm.memset.p0i8.i8(i8* nocapture, i8, i8, i32, i1) nounwind
declare void @llvm.memcpy.p0i8.p0i8.i8(i8* nocapture, i8* nocapture, i8, i32, i1) nounwind

11
llvm/test/Bitcode/attributes.ll
View File

@ -204,7 +204,7 @@ define void @f34()
; CHECK: define void @f34()
{
call void @nobuiltin() nobuiltin
; CHECK: call void @nobuiltin() #26
; CHECK: call void @nobuiltin() #27
ret void;
}
@ -256,6 +256,12 @@ define void @f43() convergent {
ret void
}
define void @f44() argmemonly
; CHECK: define void @f44() #26
{
ret void;
}
; CHECK: attributes #0 = { noreturn }
; CHECK: attributes #1 = { nounwind }
; CHECK: attributes #2 = { readnone }
@ -282,4 +288,5 @@ define void @f43() convergent {
; CHECK: attributes #23 = { noinline optnone }
; CHECK: attributes #24 = { jumptable }
; CHECK: attributes #25 = { convergent }
; CHECK: attributes #26 = { nobuiltin }
; CHECK: attributes #26 = { argmemonly }
; CHECK: attributes #27 = { nobuiltin }