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[IRGen] Zero-init stack shadow copies of values at -Onone. #16486

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Merged
merged 1 commit into from
May 11, 2018
Merged

[IRGen] Zero-init stack shadow copies of values at -Onone. #16486

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56 changes: 31 additions & 25 deletions lib/IRGen/IRGenSIL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -719,6 +719,32 @@ class IRGenSILFunction :
}
}

/// To make it unambiguous whether a `var` binding has been initialized,
/// zero-initialize the first pointer-sized field. LLDB uses this to
/// recognize to detect uninitizialized variables. This can be removed once
/// swiftc switches to @llvm.dbg.addr() intrinsics.
void zeroInit(llvm::AllocaInst *AI) {
if (!AI)
return;

// Only do this at -Onone.
if (IGM.IRGen.Opts.shouldOptimize())
return;

auto &DL = IGM.DataLayout;
if (DL.getTypeSizeInBits(AI->getAllocatedType()) <
DL.getPointerSizeInBits())
return;

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// No debug location is how LLVM marks prologue instructions.

llvm::IRBuilder<> ZeroInitBuilder(AI->getNextNode());
ZeroInitBuilder.SetCurrentDebugLocation(nullptr);
auto *BC =
ZeroInitBuilder.CreateBitCast(AI, IGM.OpaquePtrTy->getPointerTo());
ZeroInitBuilder.CreateAlignedStore(
llvm::ConstantPointerNull::get(IGM.OpaquePtrTy), BC,
IGM.getPointerAlignment().getValue());
}

/// Account for bugs in LLVM.
///
/// - The LLVM type legalizer currently doesn't update debug
Expand All @@ -742,6 +768,7 @@ class IRGenSILFunction :
auto &Alloca = ShadowStackSlots[{ArgNo, {Scope, Name}}];
if (!Alloca.isValid())
Alloca = createAlloca(Storage->getType(), Align, Name+".addr");
zeroInit(dyn_cast<llvm::AllocaInst>(Alloca.getAddress()));

ArtificialLocation AutoRestore(Scope, IGM.DebugInfo, Builder);
Builder.CreateStore(Storage, Alloca.getAddress(), Align);
Expand Down Expand Up @@ -4000,31 +4027,10 @@ void IRGenSILFunction::visitAllocStackInst(swift::AllocStackInst *i) {
if (!Decl)
return;

// To make it unambiguous whether a `var` binding has been initialized,
// zero-initialize the first pointer-sized field. LLDB uses this to
// recognize to detect uninitizialized variables. This can be removed once
// swiftc switches to @llvm.dbg.addr() intrinsics.
auto zeroInit = [&]() {
if (IGM.IRGen.Opts.shouldOptimize())
return;
Type Desugared = Decl->getType()->getDesugaredType();
if (!Desugared->getClassOrBoundGenericClass() &&
!Desugared->getStructOrBoundGenericStruct())
return;

auto *AI = dyn_cast<llvm::AllocaInst>(addr.getAddress().getAddress());
if (!AI)
return;

auto &DL = IGM.DataLayout;
if (DL.getTypeSizeInBits(AI->getAllocatedType()) < DL.getPointerSizeInBits())
return;

auto *BC = Builder.CreateBitCast(AI, IGM.OpaquePtrTy->getPointerTo());
Builder.CreateStore(llvm::ConstantPointerNull::get(IGM.OpaquePtrTy), BC,
IGM.getPointerAlignment());
};
zeroInit();
Type Desugared = Decl->getType()->getDesugaredType();
if (Desugared->getClassOrBoundGenericClass() ||
Desugared->getStructOrBoundGenericStruct())
zeroInit(dyn_cast<llvm::AllocaInst>(addr.getAddress().getAddress()));
emitDebugInfoForAllocStack(i, type, addr.getAddress().getAddress());
}

Expand Down
3 changes: 1 addition & 2 deletions test/DebugInfo/returnlocation.swift
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Expand Up @@ -12,8 +12,7 @@ import Foundation
// CHECK_NONE: define{{( protected)?}} {{.*}}void {{.*}}none
public func none(_ a: inout Int64) {
// CHECK_NONE: call void @llvm.dbg{{.*}}, !dbg
// CHECK_NONE: store{{.*}}, !dbg
// CHECK_NONE: !dbg ![[NONE_INIT:.*]]
// CHECK_NONE: store i64{{.*}}, !dbg ![[NONE_INIT:.*]]
a -= 2
// CHECK_NONE: ret {{.*}}, !dbg ![[NONE_RET:.*]]
// CHECK_NONE: ![[NONE_INIT]] = !DILocation(line: [[@LINE-2]], column:
Expand Down
2 changes: 2 additions & 0 deletions test/DebugInfo/shadowcopy-linetable.swift
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Expand Up @@ -8,6 +8,8 @@ func foo(_ x: inout Int64) {
// not.
// CHECK: %[[X:.*]] = alloca %Ts5Int64V*, align {{(4|8)}}
// CHECK-NEXT: call void @llvm.dbg.declare
// CHECK-NEXT: [[ZEROED:%[0-9]+]] = bitcast %Ts5Int64V** %[[X]] to %swift.opaque**
// CHECK-NEXT: store %swift.opaque* null, %swift.opaque** [[ZEROED]], align {{(4|8)}}
// CHECK: store %Ts5Int64V* %0, %Ts5Int64V** %[[X]], align {{(4|8)}}
// CHECK-SAME: !dbg ![[LOC0:.*]]
// CHECK-NEXT: getelementptr inbounds %Ts5Int64V, %Ts5Int64V* %0, i32 0, i32 0,
Expand Down
8 changes: 4 additions & 4 deletions test/DebugInfo/uninitialized.swift
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Expand Up @@ -8,8 +8,8 @@ public func f() {
var object: MyClass
// CHECK: %[[OBJ:.*]] = alloca %[[T1:.*]]*, align
// CHECK: call void @llvm.dbg.declare(metadata %[[T1]]** %[[OBJ]],
// CHECK: %[[BC1:.*]] = bitcast %[[T1]]** %[[OBJ]] to %swift.opaque**, !dbg
// CHECK: store %swift.opaque* null, %swift.opaque** %[[BC1]], align {{.*}}, !dbg
// CHECK: %[[BC1:.*]] = bitcast %[[T1]]** %[[OBJ]] to %swift.opaque**
// CHECK: store %swift.opaque* null, %swift.opaque** %[[BC1]], align {{.*}}
// OPT-NOT: store
// OPT: ret
}
Expand All @@ -20,8 +20,8 @@ public func g() {
var dict: Dictionary<Int64, Int64>
// CHECK: %[[DICT:.*]] = alloca %[[T2:.*]], align
// CHECK: call void @llvm.dbg.declare(metadata %[[T2]]* %[[DICT]],
// CHECK: %[[BC2:.*]] = bitcast %[[T2]]* %[[DICT]] to %swift.opaque**, !dbg
// CHECK: store %swift.opaque* null, %swift.opaque** %[[BC2]], align {{.*}}, !dbg
// CHECK: %[[BC2:.*]] = bitcast %[[T2]]* %[[DICT]] to %swift.opaque**
// CHECK: store %swift.opaque* null, %swift.opaque** %[[BC2]], align {{.*}}
// OPT-NOT: store
// OPT: ret
}