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[IC] Turn non-null MD on pointer loads to range MD on integer loads.

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Summary:
This change fixes the FIXME that you recently added when you committed
(a modified version of) my patch.  When `InstCombine` combines a load and
store of an pointer to those of an equivalently-sized integer, it currently
drops any `!nonnull` metadata that might be present.  This change replaces
`!nonnull` metadata with `!range !{ 1, -1 }` metadata instead.

Reviewers: chandlerc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D7621

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230462 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Charles Davis 2015-02-25 05:10:25 +00:00
parent 465084ffcf
commit fba7e30f0f
4 changed files with 40 additions and 11 deletions
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3
include/llvm/IR/MDBuilder.h
View File

@ -67,6 +67,9 @@ public:
/// \brief Return metadata describing the range [Lo, Hi).
MDNode *createRange(const APInt &Lo, const APInt &Hi);
/// \brief Return metadata describing the range [Lo, Hi).
MDNode *createRange(Constant *Lo, Constant *Hi);
//===------------------------------------------------------------------===//
// AA metadata.
//===------------------------------------------------------------------===//

10
lib/IR/MDBuilder.cpp
View File

@ -55,14 +55,18 @@ MDNode *MDBuilder::createBranchWeights(ArrayRef<uint32_t> Weights) {
MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {
assert(Lo.getBitWidth() == Hi.getBitWidth() && "Mismatched bitwidths!");
Type *Ty = IntegerType::get(Context, Lo.getBitWidth());
return createRange(ConstantInt::get(Ty, Lo), ConstantInt::get(Ty, Hi));
}
MDNode *MDBuilder::createRange(Constant *Lo, Constant *Hi) {
// If the range is everything then it is useless.
if (Hi == Lo)
return nullptr;
// Return the range [Lo, Hi).
Type *Ty = IntegerType::get(Context, Lo.getBitWidth());
Metadata *Range[2] = {createConstant(ConstantInt::get(Ty, Lo)),
createConstant(ConstantInt::get(Ty, Hi))};
Metadata *Range[2] = {createConstant(Lo), createConstant(Hi)};
return MDNode::get(Context, Range);
}

22
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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@ -17,6 +17,7 @@
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
@ -309,6 +310,7 @@ static LoadInst *combineLoadToNewType(InstCombiner &IC, LoadInst &LI, Type *NewT
LoadInst *NewLoad = IC.Builder->CreateAlignedLoad(
IC.Builder->CreateBitCast(Ptr, NewTy->getPointerTo(AS)),
LI.getAlignment(), LI.getName());
MDBuilder MDB(NewLoad->getContext());
for (const auto &MDPair : MD) {
unsigned ID = MDPair.first;
MDNode *N = MDPair.second;
@ -335,15 +337,27 @@ static LoadInst *combineLoadToNewType(InstCombiner &IC, LoadInst &LI, Type *NewT
break;
case LLVMContext::MD_nonnull:
// FIXME: We should translate this into range metadata for integer types
// and vice versa.
if (NewTy->isPointerTy())
// This only directly applies if the new type is also a pointer.
if (NewTy->isPointerTy()) {
NewLoad->setMetadata(ID, N);
break;
}
// If it's integral now, translate it to !range metadata.
if (NewTy->isIntegerTy()) {
auto *ITy = cast<IntegerType>(NewTy);
auto *NullInt = ConstantExpr::getPtrToInt(
ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy);
auto *NonNullInt =
ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1));
NewLoad->setMetadata(LLVMContext::MD_range,
MDB.createRange(NonNullInt, NullInt));
}
break;
case LLVMContext::MD_range:
// FIXME: It would be nice to propagate this in some way, but the type
// conversions make it hard.
// conversions make it hard. If the new type is a pointer, we could
// translate it to !nonnull metadata.
break;
}
}

16
test/Transforms/InstCombine/loadstore-metadata.ll
View File

@ -82,21 +82,29 @@ exit:
define void @test_load_cast_combine_nonnull(float** %ptr) {
; We can't preserve nonnull metadata when converting a load of a pointer to
; a load of an integer.
; FIXME: We should really transform this into range metadata and vice versa.
; a load of an integer. Instead, we translate it to range metadata.
; FIXME: We should also transform range metadata back into nonnull metadata.
; FIXME: This test is very fragile. If any LABEL lines are added after
; this point, the test will fail, because this test depends on a metadata tuple,
; which is always emitted at the end of the file. At some point, we should
; consider an option to the IR printer to emit MD tuples after the function
; that first uses them--this will allow us to refer to them like this and not
; have the tests break. For now, this function must always come last in this
; file, and no LABEL lines are to be added after this point.
;
; CHECK-LABEL: @test_load_cast_combine_nonnull(
; CHECK: %[[V:.*]] = load i64* %{{.*}}
; CHECK: %[[V:.*]] = load i64* %{{.*}}, !range ![[MD:[0-9]+]]
; CHECK-NOT: !nonnull
; CHECK: store i64 %[[V]], i64*
entry:
%p = load float** %ptr, !nonnull !3
%gep = getelementptr float** %ptr, i32 42
store float* %p, float** %gep
ret void
}
; This is the metadata tuple that we reference above:
; CHECK: ![[MD]] = !{i64 1, i64 0}
!0 = !{ !1, !1, i64 0 }
!1 = !{ !1 }
!2 = !{ !2, !1 }