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Differential D65031

WholeProgramDevirt: Teach the pass to respect the global's alignment.
ClosedPublic

Authored by pcc on Jul 19 2019, 5:03 PM.

Details

Reviewers
hctim
vitalybuka
Commits
rGef5cfc2dae07: WholeProgramDevirt: Teach the pass to respect the global's alignment.
rL366725: WholeProgramDevirt: Teach the pass to respect the global's alignment.
Summary

The bytes inserted before an overaligned global need to be padded according
to the alignment set on the original global in order for the initializer
to meet the global's alignment requirements. The previous implementation
that padded to the pointer width happened to be correct for vtables on most
platforms but may do the wrong thing if the vtable has a larger alignment.

This issue is visible with a prototype implementation of HWASAN for globals,
which will overalign all globals including vtables to 16 bytes.

There is also no padding requirement for the bytes inserted after the global
because they are never read from nor are they significant for alignment
purposes, so stop inserting padding there.

Diff Detail

Event Timeline

pcc created this revision.Jul 19 2019, 5:03 PM
Herald added a project: Restricted Project. · View Herald TranscriptJul 19 2019, 5:03 PM
Herald added a subscriber: hiraditya. · View Herald Transcript
Harbormaster completed remote builds in B35408: Diff 210939.Jul 19 2019, 5:04 PM
vitalybuka accepted this revision.Jul 22 2019, 11:32 AM
This revision is now accepted and ready to land.Jul 22 2019, 11:32 AM
Closed by commit rL366725: WholeProgramDevirt: Teach the pass to respect the global's alignment. (authored by pcc). · Explain WhyJul 22 2019, 11:51 AM
This revision was automatically updated to reflect the committed changes.

Revision Contents

PathSize
llvm/
lib/
Transforms/
IPO/
11 lines
test/
Transforms/
WholeProgramDevirt/
14 lines
16 lines

Diff 210939

llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp

Show First 20 Lines • Show All 1,296 Lines • ▼ Show 20 Linesbool DevirtModule::tryVirtualConstProp(
} }
return true; return true;
} }
void DevirtModule::rebuildGlobal(VTableBits &B) { void DevirtModule::rebuildGlobal(VTableBits &B) {
if (B.Before.Bytes.empty() && B.After.Bytes.empty()) if (B.Before.Bytes.empty() && B.After.Bytes.empty())
return; return;
// Align each byte array to pointer width. // Align the before byte array to the global's minimum alignment so that we
unsigned PointerSize = M.getDataLayout().getPointerSize(); // don't break any alignment requirements on the global.
B.Before.Bytes.resize(alignTo(B.Before.Bytes.size(), PointerSize)); unsigned Align = B.GV->getAlignment();
B.After.Bytes.resize(alignTo(B.After.Bytes.size(), PointerSize)); if (Align == 0)
Align = M.getDataLayout().getABITypeAlignment(B.GV->getValueType());
B.Before.Bytes.resize(alignTo(B.Before.Bytes.size(), Align));
// Before was stored in reverse order; flip it now. // Before was stored in reverse order; flip it now.
for (size_t I = 0, Size = B.Before.Bytes.size(); I != Size / 2; ++I) for (size_t I = 0, Size = B.Before.Bytes.size(); I != Size / 2; ++I)
std::swap(B.Before.Bytes[I], B.Before.Bytes[Size - 1 - I]); std::swap(B.Before.Bytes[I], B.Before.Bytes[Size - 1 - I]);
// Build an anonymous global containing the before bytes, followed by the // Build an anonymous global containing the before bytes, followed by the
// original initializer, followed by the after bytes. // original initializer, followed by the after bytes.
auto NewInit = ConstantStruct::getAnon( auto NewInit = ConstantStruct::getAnon(
{ConstantDataArray::get(M.getContext(), B.Before.Bytes), {ConstantDataArray::get(M.getContext(), B.Before.Bytes),
B.GV->getInitializer(), B.GV->getInitializer(),
ConstantDataArray::get(M.getContext(), B.After.Bytes)}); ConstantDataArray::get(M.getContext(), B.After.Bytes)});
auto NewGV = auto NewGV =
new GlobalVariable(M, NewInit->getType(), B.GV->isConstant(), new GlobalVariable(M, NewInit->getType(), B.GV->isConstant(),
GlobalVariable::PrivateLinkage, NewInit, "", B.GV); GlobalVariable::PrivateLinkage, NewInit, "", B.GV);
NewGV->setSection(B.GV->getSection()); NewGV->setSection(B.GV->getSection());
NewGV->setComdat(B.GV->getComdat()); NewGV->setComdat(B.GV->getComdat());
NewGV->setAlignment(B.GV->getAlignment());
// Copy the original vtable's metadata to the anonymous global, adjusting // Copy the original vtable's metadata to the anonymous global, adjusting
// offsets as required. // offsets as required.
NewGV->copyMetadata(B.GV, B.Before.Bytes.size()); NewGV->copyMetadata(B.GV, B.Before.Bytes.size());
// Build an alias named after the original global, pointing at the second // Build an alias named after the original global, pointing at the second
// element (the original initializer). // element (the original initializer).
auto Alias = GlobalAlias::create( auto Alias = GlobalAlias::create(
▲ Show 20 Lines • Show All 394 Lines • Show Last 20 Lines

llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-begin.ll

Show All 11 Lines
; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\02\02\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]] ; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\02\02\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]]
@vt2 = constant [3 x i8*] [ @vt2 = constant [3 x i8*] [
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i32 (i8*)* @vf2i32 to i8*) i8* bitcast (i32 (i8*)* @vf2i32 to i8*)
], !type !0 ], !type !0
; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\01\03\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]] ; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [5 x i8], [3 x i8*], [0 x i8] } { [5 x i8] c"\01\03\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [0 x i8] zeroinitializer }, align 1, !type [[T5:![0-9]+]]
@vt3 = constant [3 x i8*] [ @vt3 = constant [3 x i8*] [
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i32 (i8*)* @vf3i32 to i8*) i8* bitcast (i32 (i8*)* @vf3i32 to i8*)
], !type !0 ], align 1, !type !0
; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\02\04\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]] ; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [16 x i8], [3 x i8*], [0 x i8] } { [16 x i8] c"\00\00\00\00\00\00\00\00\00\00\00\02\04\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [0 x i8] zeroinitializer }, align 16, !type [[T16:![0-9]+]]
@vt4 = constant [3 x i8*] [ @vt4 = constant [3 x i8*] [
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i32 (i8*)* @vf4i32 to i8*) i8* bitcast (i32 (i8*)* @vf4i32 to i8*)
], !type !0 ], align 16, !type !0
; CHECK: @vt5 = {{.*}}, !type [[T0:![0-9]+]] ; CHECK: @vt5 = {{.*}}, !type [[T0:![0-9]+]]
@vt5 = constant [3 x i8*] [ @vt5 = constant [3 x i8*] [
i8* bitcast (void ()* @__cxa_pure_virtual to i8*), i8* bitcast (void ()* @__cxa_pure_virtual to i8*),
i8* bitcast (void ()* @__cxa_pure_virtual to i8*), i8* bitcast (void ()* @__cxa_pure_virtual to i8*),
i8* bitcast (void ()* @__cxa_pure_virtual to i8*) i8* bitcast (void ()* @__cxa_pure_virtual to i8*)
], !type !0 ], !type !0
; CHECK: @vt1 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT1DATA]], i32 0, i32 1) ; CHECK: @vt1 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT1DATA]], i32 0, i32 1)
; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT2DATA]], i32 0, i32 1) ; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT2DATA]], i32 0, i32 1)
; CHECK: @vt3 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT3DATA]], i32 0, i32 1) ; CHECK: @vt3 = alias [3 x i8*], getelementptr inbounds ({ [5 x i8], [3 x i8*], [0 x i8] }, { [5 x i8], [3 x i8*], [0 x i8] }* [[VT3DATA]], i32 0, i32 1)
; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [8 x i8], [3 x i8*], [0 x i8] }, { [8 x i8], [3 x i8*], [0 x i8] }* [[VT4DATA]], i32 0, i32 1) ; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [16 x i8], [3 x i8*], [0 x i8] }, { [16 x i8], [3 x i8*], [0 x i8] }* [[VT4DATA]], i32 0, i32 1)
define i1 @vf0i1(i8* %this) readnone { define i1 @vf0i1(i8* %this) readnone {
ret i1 0 ret i1 0
} }
define i1 @vf1i1(i8* %this) readnone { define i1 @vf1i1(i8* %this) readnone {
ret i1 1 ret i1 1
} }
▲ Show 20 Lines • Show All 76 Lines • ▼ Show 20 Linesdefine i32 @call3(i8* %obj) {
ret i32 %result ret i32 %result
} }
declare i1 @llvm.type.test(i8*, metadata) declare i1 @llvm.type.test(i8*, metadata)
declare void @llvm.assume(i1) declare void @llvm.assume(i1)
declare void @__cxa_pure_virtual() declare void @__cxa_pure_virtual()
; CHECK: [[T8]] = !{i32 8, !"typeid"} ; CHECK: [[T8]] = !{i32 8, !"typeid"}
; CHECK: [[T5]] = !{i32 5, !"typeid"}
; CHECK: [[T16]] = !{i32 16, !"typeid"}
; CHECK: [[T0]] = !{i32 0, !"typeid"} ; CHECK: [[T0]] = !{i32 0, !"typeid"}
!0 = !{i32 0, !"typeid"} !0 = !{i32 0, !"typeid"}

llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-end.ll

; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s ; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
target datalayout = "e-p:64:64" target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu" target triple = "x86_64-unknown-linux-gnu"
; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf1i32 to i8*)], [8 x i8] c"\01\00\00\00\01\00\00\00" }, !type [[T8:![0-9]+]] ; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf1i32 to i8*)], [5 x i8] c"\01\00\00\00\01" }, !type [[T8:![0-9]+]]
@vt1 = constant [4 x i8*] [ @vt1 = constant [4 x i8*] [
i8* null, i8* null,
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i32 (i8*)* @vf1i32 to i8*) i8* bitcast (i32 (i8*)* @vf1i32 to i8*)
], !type !1 ], !type !1
; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [8 x i8] c"\02\00\00\00\02\00\00\00" }, !type [[T0:![0-9]+]] ; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [5 x i8] c"\02\00\00\00\02" }, !type [[T0:![0-9]+]]
@vt2 = constant [3 x i8*] [ @vt2 = constant [3 x i8*] [
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i32 (i8*)* @vf2i32 to i8*) i8* bitcast (i32 (i8*)* @vf2i32 to i8*)
], !type !0 ], !type !0
; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [8 x i8] c"\03\00\00\00\01\00\00\00" }, !type [[T8]] ; CHECK: [[VT3DATA:@[^ ]*]] = private constant { [0 x i8], [4 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [4 x i8*] [i8* null, i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf3i32 to i8*)], [5 x i8] c"\03\00\00\00\01" }, !type [[T8]]
@vt3 = constant [4 x i8*] [ @vt3 = constant [4 x i8*] [
i8* null, i8* null,
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i32 (i8*)* @vf3i32 to i8*) i8* bitcast (i32 (i8*)* @vf3i32 to i8*)
], !type !1 ], !type !1
; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [8 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [8 x i8] c"\04\00\00\00\02\00\00\00" }, !type [[T0]] ; CHECK: [[VT4DATA:@[^ ]*]] = private constant { [0 x i8], [3 x i8*], [5 x i8] } { [0 x i8] zeroinitializer, [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf4i32 to i8*)], [5 x i8] c"\04\00\00\00\02" }, !type [[T0]]
@vt4 = constant [3 x i8*] [ @vt4 = constant [3 x i8*] [
i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
i8* bitcast (i32 (i8*)* @vf4i32 to i8*) i8* bitcast (i32 (i8*)* @vf4i32 to i8*)
], !type !0 ], !type !0
; CHECK: @vt1 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [8 x i8] }, { [0 x i8], [4 x i8*], [8 x i8] }* [[VT1DATA]], i32 0, i32 1) ; CHECK: @vt1 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [5 x i8] }, { [0 x i8], [4 x i8*], [5 x i8] }* [[VT1DATA]], i32 0, i32 1)
; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [8 x i8] }, { [0 x i8], [3 x i8*], [8 x i8] }* [[VT2DATA]], i32 0, i32 1) ; CHECK: @vt2 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [5 x i8] }, { [0 x i8], [3 x i8*], [5 x i8] }* [[VT2DATA]], i32 0, i32 1)
; CHECK: @vt3 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [8 x i8] }, { [0 x i8], [4 x i8*], [8 x i8] }* [[VT3DATA]], i32 0, i32 1) ; CHECK: @vt3 = alias [4 x i8*], getelementptr inbounds ({ [0 x i8], [4 x i8*], [5 x i8] }, { [0 x i8], [4 x i8*], [5 x i8] }* [[VT3DATA]], i32 0, i32 1)
; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [8 x i8] }, { [0 x i8], [3 x i8*], [8 x i8] }* [[VT4DATA]], i32 0, i32 1) ; CHECK: @vt4 = alias [3 x i8*], getelementptr inbounds ({ [0 x i8], [3 x i8*], [5 x i8] }, { [0 x i8], [3 x i8*], [5 x i8] }* [[VT4DATA]], i32 0, i32 1)
define i1 @vf0i1(i8* %this) readnone { define i1 @vf0i1(i8* %this) readnone {
ret i1 0 ret i1 0
} }
define i1 @vf1i1(i8* %this) readnone { define i1 @vf1i1(i8* %this) readnone {
ret i1 1 ret i1 1
} }
▲ Show 20 Lines • Show All 87 Lines • Show Last 20 Lines