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PR for llvm/llvm-project#53559 #66

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Feb 21, 2022
Merged

PR for llvm/llvm-project#53559 #66

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2 changes: 1 addition & 1 deletion llvm/include/llvm/Analysis/MemoryBuiltins.h
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Original file line number Diff line number Diff line change
Expand Up @@ -210,7 +210,6 @@ class ObjectSizeOffsetVisitor
SizeOffsetType visitConstantPointerNull(ConstantPointerNull&);
SizeOffsetType visitExtractElementInst(ExtractElementInst &I);
SizeOffsetType visitExtractValueInst(ExtractValueInst &I);
SizeOffsetType visitGEPOperator(GEPOperator &GEP);
SizeOffsetType visitGlobalAlias(GlobalAlias &GA);
SizeOffsetType visitGlobalVariable(GlobalVariable &GV);
SizeOffsetType visitIntToPtrInst(IntToPtrInst&);
Expand All @@ -221,6 +220,7 @@ class ObjectSizeOffsetVisitor
SizeOffsetType visitInstruction(Instruction &I);

private:
SizeOffsetType computeImpl(Value *V);
bool CheckedZextOrTrunc(APInt &I);
};

Expand Down
51 changes: 33 additions & 18 deletions llvm/lib/Analysis/MemoryBuiltins.cpp
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Expand Up @@ -573,18 +573,48 @@ ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
}

SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
unsigned InitialIntTyBits = DL.getIndexTypeSizeInBits(V->getType());

// Stripping pointer casts can strip address space casts which can change the
// index type size. The invariant is that we use the value type to determine
// the index type size and if we stripped address space casts we have to
// readjust the APInt as we pass it upwards in order for the APInt to match
// the type the caller passed in.
APInt Offset(InitialIntTyBits, 0);
V = V->stripAndAccumulateConstantOffsets(
DL, Offset, /* AllowNonInbounds */ true, /* AllowInvariantGroup */ true);

// Later we use the index type size and zero but it will match the type of the
// value that is passed to computeImpl.
IntTyBits = DL.getIndexTypeSizeInBits(V->getType());
Zero = APInt::getZero(IntTyBits);

V = V->stripPointerCasts();
bool IndexTypeSizeChanged = InitialIntTyBits != IntTyBits;
if (!IndexTypeSizeChanged && Offset.isZero())
return computeImpl(V);

// We stripped an address space cast that changed the index type size or we
// accumulated some constant offset (or both). Readjust the bit width to match
// the argument index type size and apply the offset, as required.
SizeOffsetType SOT = computeImpl(V);
if (IndexTypeSizeChanged) {
if (knownSize(SOT) && !::CheckedZextOrTrunc(SOT.first, InitialIntTyBits))
SOT.first = APInt();
if (knownOffset(SOT) && !::CheckedZextOrTrunc(SOT.second, InitialIntTyBits))
SOT.second = APInt();
}
// If the computed offset is "unknown" we cannot add the stripped offset.
return {SOT.first,
SOT.second.getBitWidth() > 1 ? SOT.second + Offset : SOT.second};
}

SizeOffsetType ObjectSizeOffsetVisitor::computeImpl(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V)) {
// If we have already seen this instruction, bail out. Cycles can happen in
// unreachable code after constant propagation.
if (!SeenInsts.insert(I).second)
return unknown();

if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
return visitGEPOperator(*GEP);
return visit(*I);
}
if (Argument *A = dyn_cast<Argument>(V))
Expand All @@ -597,12 +627,6 @@ SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
return visitGlobalVariable(*GV);
if (UndefValue *UV = dyn_cast<UndefValue>(V))
return visitUndefValue(*UV);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() == Instruction::IntToPtr)
return unknown(); // clueless
if (CE->getOpcode() == Instruction::GetElementPtr)
return visitGEPOperator(cast<GEPOperator>(*CE));
}

LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: "
<< *V << '\n');
Expand Down Expand Up @@ -682,15 +706,6 @@ ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
return unknown();
}

SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
SizeOffsetType PtrData = compute(GEP.getPointerOperand());
APInt Offset(DL.getIndexTypeSizeInBits(GEP.getPointerOperand()->getType()), 0);
if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
return unknown();

return std::make_pair(PtrData.first, PtrData.second + Offset);
}

SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
if (GA.isInterposable())
return unknown();
Expand Down
39 changes: 38 additions & 1 deletion llvm/test/Transforms/InstCombine/builtin-dynamic-object-size.ll
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@@ -1,6 +1,6 @@
; RUN: opt -instcombine -S < %s | FileCheck %s

target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128-p7:32:32"
target triple = "x86_64-apple-macosx10.14.0"

; Function Attrs: nounwind ssp uwtable
Expand Down Expand Up @@ -152,6 +152,43 @@ if.end: ; preds = %if.else, %if.then
; CHECK-NEXT: br i1 false, label %if.else, label %if.then
; CHECK: call void @fortified_chk(i8* %obj, i64 [[SZ]])

@p7 = internal addrspace(7) global i8 0

; Gracefully handle AS cast when the address spaces have different pointer widths.
define i64 @as_cast(i1 %c) {
; CHECK: [[TMP0:%.*]] = select i1 %c, i64 64, i64 1
; CHECK: [[NOT:%.*]] = xor i1 %c, true
; CHECK: [[NEG:%.*]] = sext i1 [[NOT]] to i64
; CHECK: [[TMP1:%.*]] = add nsw i64 [[TMP0]], [[NEG]]
; CHECK: [[TMP2:%.*]] = icmp ne i64 [[TMP1]], -1
; CHECK: call void @llvm.assume(i1 [[TMP2]])
; CHECK: ret i64 [[TMP1]]
;
entry:
%p0 = tail call i8* @malloc(i64 64)
%gep = getelementptr i8, i8 addrspace(7)* @p7, i32 1
%as = addrspacecast i8 addrspace(7)* %gep to i8*
%select = select i1 %c, i8* %p0, i8* %as
%calc_size = tail call i64 @llvm.objectsize.i64.p0i8(i8* %select, i1 false, i1 true, i1 true)
ret i64 %calc_size
}

define i64 @constexpr_as_cast(i1 %c) {
; CHECK: [[TMP0:%.*]] = select i1 %c, i64 64, i64 1
; CHECK: [[NOT:%.*]] = xor i1 %c, true
; CHECK: [[NEG:%.*]] = sext i1 [[NOT]] to i64
; CHECK: [[TMP1:%.*]] = add nsw i64 [[TMP0]], [[NEG]]
; CHECK: [[TMP2:%.*]] = icmp ne i64 [[TMP1]], -1
; CHECK: call void @llvm.assume(i1 [[TMP2]])
; CHECK: ret i64 [[TMP1]]
;
entry:
%p0 = tail call i8* @malloc(i64 64)
%select = select i1 %c, i8* %p0, i8* addrspacecast (i8 addrspace(7)* getelementptr (i8, i8 addrspace(7)* @p7, i32 1) to i8*)
%calc_size = tail call i64 @llvm.objectsize.i64.p0i8(i8* %select, i1 false, i1 true, i1 true)
ret i64 %calc_size
}

declare void @bury(i32) local_unnamed_addr #2

; Function Attrs: nounwind allocsize(0)
Expand Down