tbaeder updated this revision to Diff 521082.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D150209/new/
https://reviews.llvm.org/D150209
Files:
clang/lib/AST/Interp/Integral.h
clang/lib/AST/Interp/Interp.h
clang/test/AST/Interp/shifts.cpp
Index: clang/test/AST/Interp/shifts.cpp
===================================================================
--- clang/test/AST/Interp/shifts.cpp
+++ clang/test/AST/Interp/shifts.cpp
@@ -152,4 +152,21 @@
constexpr signed int R = (sizeof(unsigned) * 8) + 1;
constexpr decltype(L) M = (R > 32 && R < 64) ? L << R : 0;
constexpr decltype(L) M2 = (R > 32 && R < 64) ? L >> R : 0;
+
+
+ constexpr int signedShift() { // cxx17-error {{never produces a constant
expression}} \
+ // ref-cxx17-error {{never produces a constant
expression}}
+ return 1024 << 31; // cxx17-warning {{signed shift result}} \
+ // ref-cxx17-warning {{signed shift result}} \
+ // cxx17-note {{signed left shift discards bits}} \
+ // ref-cxx17-note {{signed left shift discards bits}}
+ }
+
+ constexpr int negativeShift() { // cxx17-error {{never produces a constant
expression}} \
+ // ref-cxx17-error {{never produces a
constant expression}}
+ return -1 << 2; // cxx17-warning {{shifting a negative signed value is
undefined}} \
+ // ref-cxx17-warning {{shifting a negative signed value is
undefined}} \
+ // cxx17-note {{left shift of negative value -1}} \
+ // ref-cxx17-note {{left shift of negative value -1}}
+ }
};
Index: clang/lib/AST/Interp/Interp.h
===================================================================
--- clang/lib/AST/Interp/Interp.h
+++ clang/lib/AST/Interp/Interp.h
@@ -109,8 +109,9 @@
bool CheckCtorCall(InterpState &S, CodePtr OpPC, const Pointer &This);
/// Checks if the shift operation is legal.
-template <typename RT>
-bool CheckShift(InterpState &S, CodePtr OpPC, const RT &RHS, unsigned Bits) {
+template <typename LT, typename RT>
+bool CheckShift(InterpState &S, CodePtr OpPC, const LT &LHS, const RT &RHS,
+ unsigned Bits) {
if (RHS.isNegative()) {
const SourceInfo &Loc = S.Current->getSource(OpPC);
S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt();
@@ -126,6 +127,20 @@
S.CCEDiag(E, diag::note_constexpr_large_shift) << Val << Ty << Bits;
return false;
}
+
+ if (LHS.isSigned() && !S.getLangOpts().CPlusPlus20) {
+ const Expr *E = S.Current->getExpr(OpPC);
+ // C++11 [expr.shift]p2: A signed left shift must have a non-negative
+ // operand, and must not overflow the corresponding unsigned type.
+ if (LHS.isNegative())
+ S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS.toAPSInt();
+ else if (LHS.toUnsigned().countLeadingZeros() < static_cast<unsigned>(RHS))
+ S.CCEDiag(E, diag::note_constexpr_lshift_discards);
+ }
+
+ // C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+ // E1 x 2^E2 module 2^N.
+
return true;
}
@@ -1612,7 +1627,7 @@
const auto &LHS = S.Stk.pop<LT>();
const unsigned Bits = LHS.bitWidth();
- if (!CheckShift<RT>(S, OpPC, RHS, Bits))
+ if (!CheckShift(S, OpPC, LHS, RHS, Bits))
return false;
Integral<LT::bitWidth(), false> R;
@@ -1629,7 +1644,7 @@
const auto &LHS = S.Stk.pop<LT>();
const unsigned Bits = LHS.bitWidth();
- if (!CheckShift<RT>(S, OpPC, RHS, Bits))
+ if (!CheckShift(S, OpPC, LHS, RHS, Bits))
return false;
Integral<LT::bitWidth(), false> R;
Index: clang/lib/AST/Interp/Integral.h
===================================================================
--- clang/lib/AST/Interp/Integral.h
+++ clang/lib/AST/Interp/Integral.h
@@ -127,7 +127,11 @@
return Compare(V, RHS.V);
}
- unsigned countLeadingZeros() const { return llvm::countl_zero<ReprT>(V); }
+ unsigned countLeadingZeros() const {
+ if constexpr (!Signed)
+ return llvm::countl_zero<ReprT>(V);
+ llvm_unreachable("Don't call countLeadingZeros() on signed types.");
+ }
Integral truncate(unsigned TruncBits) const {
if (TruncBits >= Bits)
Index: clang/test/AST/Interp/shifts.cpp
===================================================================
--- clang/test/AST/Interp/shifts.cpp
+++ clang/test/AST/Interp/shifts.cpp
@@ -152,4 +152,21 @@
constexpr signed int R = (sizeof(unsigned) * 8) + 1;
constexpr decltype(L) M = (R > 32 && R < 64) ? L << R : 0;
constexpr decltype(L) M2 = (R > 32 && R < 64) ? L >> R : 0;
+
+
+ constexpr int signedShift() { // cxx17-error {{never produces a constant expression}} \
+ // ref-cxx17-error {{never produces a constant expression}}
+ return 1024 << 31; // cxx17-warning {{signed shift result}} \
+ // ref-cxx17-warning {{signed shift result}} \
+ // cxx17-note {{signed left shift discards bits}} \
+ // ref-cxx17-note {{signed left shift discards bits}}
+ }
+
+ constexpr int negativeShift() { // cxx17-error {{never produces a constant expression}} \
+ // ref-cxx17-error {{never produces a constant expression}}
+ return -1 << 2; // cxx17-warning {{shifting a negative signed value is undefined}} \
+ // ref-cxx17-warning {{shifting a negative signed value is undefined}} \
+ // cxx17-note {{left shift of negative value -1}} \
+ // ref-cxx17-note {{left shift of negative value -1}}
+ }
};
Index: clang/lib/AST/Interp/Interp.h
===================================================================
--- clang/lib/AST/Interp/Interp.h
+++ clang/lib/AST/Interp/Interp.h
@@ -109,8 +109,9 @@
bool CheckCtorCall(InterpState &S, CodePtr OpPC, const Pointer &This);
/// Checks if the shift operation is legal.
-template <typename RT>
-bool CheckShift(InterpState &S, CodePtr OpPC, const RT &RHS, unsigned Bits) {
+template <typename LT, typename RT>
+bool CheckShift(InterpState &S, CodePtr OpPC, const LT &LHS, const RT &RHS,
+ unsigned Bits) {
if (RHS.isNegative()) {
const SourceInfo &Loc = S.Current->getSource(OpPC);
S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt();
@@ -126,6 +127,20 @@
S.CCEDiag(E, diag::note_constexpr_large_shift) << Val << Ty << Bits;
return false;
}
+
+ if (LHS.isSigned() && !S.getLangOpts().CPlusPlus20) {
+ const Expr *E = S.Current->getExpr(OpPC);
+ // C++11 [expr.shift]p2: A signed left shift must have a non-negative
+ // operand, and must not overflow the corresponding unsigned type.
+ if (LHS.isNegative())
+ S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS.toAPSInt();
+ else if (LHS.toUnsigned().countLeadingZeros() < static_cast<unsigned>(RHS))
+ S.CCEDiag(E, diag::note_constexpr_lshift_discards);
+ }
+
+ // C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+ // E1 x 2^E2 module 2^N.
+
return true;
}
@@ -1612,7 +1627,7 @@
const auto &LHS = S.Stk.pop<LT>();
const unsigned Bits = LHS.bitWidth();
- if (!CheckShift<RT>(S, OpPC, RHS, Bits))
+ if (!CheckShift(S, OpPC, LHS, RHS, Bits))
return false;
Integral<LT::bitWidth(), false> R;
@@ -1629,7 +1644,7 @@
const auto &LHS = S.Stk.pop<LT>();
const unsigned Bits = LHS.bitWidth();
- if (!CheckShift<RT>(S, OpPC, RHS, Bits))
+ if (!CheckShift(S, OpPC, LHS, RHS, Bits))
return false;
Integral<LT::bitWidth(), false> R;
Index: clang/lib/AST/Interp/Integral.h
===================================================================
--- clang/lib/AST/Interp/Integral.h
+++ clang/lib/AST/Interp/Integral.h
@@ -127,7 +127,11 @@
return Compare(V, RHS.V);
}
- unsigned countLeadingZeros() const { return llvm::countl_zero<ReprT>(V); }
+ unsigned countLeadingZeros() const {
+ if constexpr (!Signed)
+ return llvm::countl_zero<ReprT>(V);
+ llvm_unreachable("Don't call countLeadingZeros() on signed types.");
+ }
Integral truncate(unsigned TruncBits) const {
if (TruncBits >= Bits)
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