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Widen EHScope::ClenupBitFields::FixupDepth to avoid overflowing it (PR23490) 

It currently only takes 2048 gotos to overflow the FixupDepth bitfield,
causing silent miscompilation. Apparently some parser generators run into
this (see PR).

I don't know that that data structure is terribly size sensitive anyway,
and since there's no room to widen the bitfield, let's just use a separate
word in EHCatchScope for it.

Differential Revision: http://reviews.llvm.org/D21566

llvm-svn: 273434
This commit is contained in:
Hans Wennborg 2016-06-22 16:21:14 +00:00
parent 0df350589f
commit 9565cf581e
2 changed files with 37 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
clang/lib/CodeGen/CGCleanup.h
View File

@ -86,11 +86,6 @@ protected:
/// The amount of extra storage needed by the Cleanup.
/// Always a multiple of the scope-stack alignment.
unsigned CleanupSize : 12;
/// The number of fixups required by enclosing scopes (not including
/// this one). If this is the top cleanup scope, all the fixups
/// from this index onwards belong to this scope.
unsigned FixupDepth : 32 - 18 - NumCommonBits; // currently 12
};
class FilterBitFields {
@ -188,6 +183,7 @@ public:
EHScopeStack::stable_iterator enclosingEHScope)
: EHScope(Catch, enclosingEHScope) {
CatchBits.NumHandlers = numHandlers;
assert(CatchBits.NumHandlers == numHandlers && "NumHandlers overflow?");
}
unsigned getNumHandlers() const {
@ -263,6 +259,11 @@ class LLVM_ALIGNAS(/*alignof(uint64_t)*/ 8) EHCleanupScope : public EHScope {
};
mutable struct ExtInfo *ExtInfo;
/// The number of fixups required by enclosing scopes (not including
/// this one). If this is the top cleanup scope, all the fixups
/// from this index onwards belong to this scope.
unsigned FixupDepth;
struct ExtInfo &getExtInfo() {
if (!ExtInfo) ExtInfo = new struct ExtInfo();
return *ExtInfo;
@ -288,8 +289,9 @@ public:
unsigned cleanupSize, unsigned fixupDepth,
EHScopeStack::stable_iterator enclosingNormal,
EHScopeStack::stable_iterator enclosingEH)
: EHScope(EHScope::Cleanup, enclosingEH), EnclosingNormal(enclosingNormal),
NormalBlock(nullptr), ActiveFlag(nullptr), ExtInfo(nullptr) {
: EHScope(EHScope::Cleanup, enclosingEH),
EnclosingNormal(enclosingNormal), NormalBlock(nullptr),
ActiveFlag(nullptr), ExtInfo(nullptr), FixupDepth(fixupDepth) {
CleanupBits.IsNormalCleanup = isNormal;
CleanupBits.IsEHCleanup = isEH;
CleanupBits.IsActive = isActive;
@ -297,7 +299,6 @@ public:
CleanupBits.TestFlagInNormalCleanup = false;
CleanupBits.TestFlagInEHCleanup = false;
CleanupBits.CleanupSize = cleanupSize;
CleanupBits.FixupDepth = fixupDepth;
assert(CleanupBits.CleanupSize == cleanupSize && "cleanup size overflow");
}
@ -343,7 +344,7 @@ public:
return CleanupBits.TestFlagInEHCleanup;
}
unsigned getFixupDepth() const { return CleanupBits.FixupDepth; }
unsigned getFixupDepth() const { return FixupDepth; }
EHScopeStack::stable_iterator getEnclosingNormalCleanup() const {
return EnclosingNormal;
}
@ -451,6 +452,7 @@ public:
EHFilterScope(unsigned numFilters)
: EHScope(Filter, EHScopeStack::stable_end()) {
FilterBits.NumFilters = numFilters;
assert(FilterBits.NumFilters == numFilters && "NumFilters overflow");
}
static size_t getSizeForNumFilters(unsigned numFilters) {

26
clang/test/CodeGen/fixup-depth-overflow.c Normal file
View File

@ -0,0 +1,26 @@
// RUN: %clang_cc1 -O1 -disable-llvm-optzns -emit-llvm -o - %s | FileCheck %s
#define M if (x) goto L1;
#define M10 M M M M M M M M M M
#define M100 M10 M10 M10 M10 M10 M10 M10 M10 M10 M10
#define M1000 M100 M100 M100 M100 M100 M100 M100 M100 M100 M100
void f(int x) {
int h;
// Many gotos to not-yet-emitted labels would cause EHScope's FixupDepth
// to overflow (PR23490).
M1000 M1000 M1000
if (x == 5) {
// This will cause us to emit a clean-up of the stack variable. If the
// FixupDepths are broken, fixups will erroneously get threaded through it.
int i;
}
L1:
return;
}
// CHECK-LABEL: define void @f
// CHECK-NOT: cleanup