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[clang] Change the condition of unnecessary packed warning 

Summary:
Change the condition of this unnecessary packed warning. The packed is unnecessary when
1. the alignment of the struct/class won't alter.
2. the size is unchanged.
3. the offset of each field is the same.

Remove all field-level warning.

Reviewers: chh, akyrtzi, rtrieu

Reviewed By: chh

Subscribers: rsmith, srhines, cfe-commits, xazax.hun

Differential Revision: https://reviews.llvm.org/D34114

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@309750 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Yan Wang 2017-08-01 21:41:39 +00:00
parent b3d4dafef1
commit d93a902201
2 changed files with 98 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
lib/AST/RecordLayoutBuilder.cpp
View File

@ -632,6 +632,9 @@ protected:
/// pointer, as opposed to inheriting one from a primary base class.
bool HasOwnVFPtr;
/// \brief the flag of field offset changing due to packed attribute.
bool HasPackedField;
typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
/// Bases - base classes and their offsets in the record.
@ -666,7 +669,7 @@ protected:
NonVirtualSize(CharUnits::Zero()),
NonVirtualAlignment(CharUnits::One()), PrimaryBase(nullptr),
PrimaryBaseIsVirtual(false), HasOwnVFPtr(false),
FirstNearlyEmptyVBase(nullptr) {}
HasPackedField(false), FirstNearlyEmptyVBase(nullptr) {}
void Layout(const RecordDecl *D);
void Layout(const CXXRecordDecl *D);
@ -1847,7 +1850,6 @@ void ItaniumRecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastUnit;
uint64_t UnpackedSizeInBits =
llvm::alignTo(getSizeInBits(), Context.toBits(UnpackedAlignment));
CharUnits UnpackedSize = Context.toCharUnitsFromBits(UnpackedSizeInBits);
uint64_t RoundedSize =
llvm::alignTo(getSizeInBits(), Context.toBits(Alignment));
@ -1882,10 +1884,11 @@ void ItaniumRecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
<< (InBits ? 1 : 0); // (byte|bit)
}
// Warn if we packed it unnecessarily. If the alignment is 1 byte don't
// bother since there won't be alignment issues.
if (Packed && UnpackedAlignment > CharUnits::One() &&
getSize() == UnpackedSize)
// Warn if we packed it unnecessarily, when the unpacked alignment is not
// greater than the one after packing, the size in bits doesn't change and
// the offset of each field is identical.
if (Packed && UnpackedAlignment <= Alignment &&
UnpackedSizeInBits == getSizeInBits() && !HasPackedField)
Diag(D->getLocation(), diag::warn_unnecessary_packed)
<< Context.getTypeDeclType(RD);
}
@ -1977,13 +1980,10 @@ void ItaniumRecordLayoutBuilder::CheckFieldPadding(
<< Context.getTypeDeclType(D->getParent())
<< PadSize
<< (InBits ? 1 : 0); // (byte|bit)
}
// Warn if we packed it unnecessarily. If the alignment is 1 byte don't
// bother since there won't be alignment issues.
if (isPacked && UnpackedAlign > CharBitNum && Offset == UnpackedOffset)
Diag(D->getLocation(), diag::warn_unnecessary_packed)
<< D->getIdentifier();
}
if (isPacked && Offset != UnpackedOffset) {
HasPackedField = true;
}
}
static const CXXMethodDecl *computeKeyFunction(ASTContext &Context,

93
test/CodeGenCXX/warn-padded-packed.cpp
View File

@ -17,7 +17,7 @@ struct S3 {
} __attribute__((packed));
struct S4 {
int i; // expected-warning {{packed attribute is unnecessary for 'i'}}
int i;
char c;
} __attribute__((packed));
@ -46,18 +46,18 @@ struct S8 : B {
int i; // expected-warning {{padding struct 'S8' with 3 bytes to align 'i'}}
};
struct S9 { // expected-warning {{packed attribute is unnecessary for 'S9'}}
int x; // expected-warning {{packed attribute is unnecessary for 'x'}}
int y; // expected-warning {{packed attribute is unnecessary for 'y'}}
struct S9 {
int x;
int y;
} __attribute__((packed));
struct S10 { // expected-warning {{packed attribute is unnecessary for 'S10'}}
int x; // expected-warning {{packed attribute is unnecessary for 'x'}}
struct S10 {
int x;
char a,b,c,d;
} __attribute__((packed));
struct S11 {
struct S11 { // expected-warning {{packed attribute is unnecessary for 'S11'}}
bool x;
char a,b,c,d;
} __attribute__((packed));
@ -72,5 +72,82 @@ struct S13 { // expected-warning {{padding size of 'S13' with 6 bits to alignmen
bool b : 10;
};
struct S14 { // expected-warning {{packed attribute is unnecessary for 'S14'}}
char a,b,c,d;
} __attribute__((packed));
struct S15 { // expected-warning {{packed attribute is unnecessary for 'S15'}}
struct S14 s;
char a;
} __attribute__((packed));
struct S16 { // expected-warning {{padding size of 'S16' with 2 bytes to alignment boundary}} expected-warning {{packed attribute is unnecessary for 'S16'}}
char a,b;
} __attribute__((packed, aligned(4)));
struct S17 {
struct S16 s;
char a,b;
} __attribute__((packed, aligned(2)));
struct S18 { // expected-warning {{padding size of 'S18' with 2 bytes to alignment boundary}} expected-warning {{packed attribute is unnecessary for 'S18'}}
struct S16 s;
char a,b;
} __attribute__((packed, aligned(4)));
struct S19 { // expected-warning {{packed attribute is unnecessary for 'S19'}}
bool b;
char a;
} __attribute__((packed, aligned(1)));
struct S20 {
int i;
char a;
} __attribute__((packed, aligned(1)));
struct S21 { // expected-warning {{padding size of 'S21' with 4 bits to alignment boundary}}
unsigned char a : 6;
unsigned char b : 6;
} __attribute__((packed, aligned(1)));
struct S22 { // expected-warning {{packed attribute is unnecessary for 'S22'}}
unsigned char a : 4;
unsigned char b : 4;
} __attribute__((packed));
struct S23 { // expected-warning {{padding size of 'S23' with 4 bits to alignment boundary}} expected-warning {{packed attribute is unnecessary for 'S23'}}
unsigned char a : 2;
unsigned char b : 2;
} __attribute__((packed));
struct S24 {
unsigned char a : 6;
unsigned char b : 6;
unsigned char c : 6;
unsigned char d : 6;
unsigned char e : 6;
unsigned char f : 6;
unsigned char g : 6;
unsigned char h : 6;
} __attribute__((packed));
struct S25 { // expected-warning {{padding size of 'S25' with 7 bits to alignment boundary}} expected-warning {{packed attribute is unnecessary for 'S25'}}
unsigned char a;
unsigned char b : 1;
} __attribute__((packed));
struct S26 { // expected-warning {{packed attribute is unnecessary for 'S26'}}
unsigned char a : 1;
unsigned char b; //expected-warning {{padding struct 'S26' with 7 bits to align 'b'}}
} __attribute__((packed));
struct S27 { // expected-warning {{padding size of 'S27' with 7 bits to alignment boundary}}
unsigned char a : 1;
unsigned char b : 8;
} __attribute__((packed));
// The warnings are emitted when the layout of the structs is computed, so we have to use them.
void f(S1*, S2*, S3*, S4*, S5*, S6*, S7*, S8*, S9*, S10*, S11*, S12*, S13*) { }
void f(S1*, S2*, S3*, S4*, S5*, S6*, S7*, S8*, S9*, S10*, S11*, S12*, S13*,
S14*, S15*, S16*, S17*, S18*, S19*, S20*, S21*, S22*, S23*, S24*, S25*,
S26*, S27*){}