[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGd6b0af0574ca: [clang][Interp] Add more shift error checking 
(authored by tbaeder).

Repository:
  rG LLVM Github Monorepo

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 +152,39 @@
   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}}
+  }
+
+  constexpr int foo(int a) {
+return -a << 2; // cxx17-note {{left shift of negative value -10}} \
+// ref-cxx17-note {{left shift of negative value -10}} \
+// cxx17-note {{left shift of negative value -2}} \
+// ref-cxx17-note {{left shift of negative value -2}}
+  }
+  static_assert(foo(10)); // cxx17-error {{not an integral constant expression}} \
+  // cxx17-note {{in call to 'foo(10)'}} \
+  // ref-cxx17-error {{not an integral constant expression}} \
+  // ref-cxx17-note {{in call to 'foo(10)'}}
+
+  constexpr int a = -2;
+  static_assert(foo(a));
+  static_assert(foo(-a)); // cxx17-error {{not an integral constant expression}} \
+  // cxx17-note {{in call to 'foo(2)'}} \
+  // ref-cxx17-error {{not an integral constant expression}} \
+  // ref-cxx17-note {{in call to 'foo(2)'}}
 };
Index: clang/lib/AST/Interp/Interp.h
===
--- clang/lib/AST/Interp/Interp.h
+++ clang/lib/AST/Interp/Interp.h
@@ -105,8 +105,9 @@
 bool CheckCtorCall(InterpState , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = S.Current->getSource(OpPC);
 S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt();
@@ -122,6 +123,20 @@
 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(RHS))
+  S.CCEDiag(E, diag::note_constexpr_lshift_discards);
+  }
+
+  // C++2a [expr.shift]p2: [P0907R4]:
+  //E1 << E2 is the unique value congruent to
+  //E1 x 2^E2 module 2^N.
   return true;
 }
 
@@ -1523,7 +1538,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1540,7 +1555,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added a comment.

LGTM!


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150209/new/

https://reviews.llvm.org/D150209

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 526965.
tbaeder marked an inline comment as done.

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 +152,39 @@
   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}}
+  }
+
+  constexpr int foo(int a) {
+return -a << 2; // cxx17-note {{left shift of negative value -10}} \
+// ref-cxx17-note {{left shift of negative value -10}} \
+// cxx17-note {{left shift of negative value -2}} \
+// ref-cxx17-note {{left shift of negative value -2}}
+  }
+  static_assert(foo(10)); // cxx17-error {{not an integral constant expression}} \
+  // cxx17-note {{in call to 'foo(10)'}} \
+  // ref-cxx17-error {{not an integral constant expression}} \
+  // ref-cxx17-note {{in call to 'foo(10)'}}
+
+  constexpr int a = -2;
+  static_assert(foo(a));
+  static_assert(foo(-a)); // cxx17-error {{not an integral constant expression}} \
+  // cxx17-note {{in call to 'foo(2)'}} \
+  // ref-cxx17-error {{not an integral constant expression}} \
+  // ref-cxx17-note {{in call to 'foo(2)'}}
 };
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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = 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(RHS))
+  S.CCEDiag(E, diag::note_constexpr_lshift_discards);
+  }
+
+  // C++2a [expr.shift]p2: [P0907R4]:
+  //E1 << E2 is the unique value congruent to
+  //E1 x 2^E2 module 2^N.
   return true;
 }
 
@@ -1612,7 +1627,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1629,7 +1644,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  unsigned countLeadingZeros() const {
+if constexpr (!Signed)
+  return llvm::countl_zero(V);
+llvm_unreachable("Don't 

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.



Comment at: clang/test/AST/Interp/shifts.cpp:165-171
+  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}}
+  }

I'd like a test along the lines of:
```
constexpr int foo(int a) {
  return -a << 2;
}
static_assert(foo(10)); // Should fail
constexpr int a = -2;
static_assert(foo(a)); // Should be fine
static_assert(foo(-a)); // Should fail
```


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150209/new/

https://reviews.llvm.org/D150209

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 521237.
tbaeder marked an inline comment as done.

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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = 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(RHS))
+  S.CCEDiag(E, diag::note_constexpr_lshift_discards);
+  }
+
+  // C++2a [expr.shift]p2: [P0907R4]:
+  //E1 << E2 is the unique value congruent to
+  //E1 x 2^E2 module 2^N.
   return true;
 }
 
@@ -1612,7 +1627,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1629,7 +1644,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  unsigned countLeadingZeros() const {
+if constexpr (!Signed)
+  return llvm::countl_zero(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}}
+  

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik accepted this revision.
shafik added a comment.
This revision is now accepted and ready to land.

LGTM




Comment at: clang/lib/AST/Interp/Interp.h:141-142
+
+  // C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+  // E1 x 2^E2 module 2^N.
+

Just adding a reference to 
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0907r4.html since 
that is the paper that changed this behavior


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150209/new/

https://reviews.llvm.org/D150209

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = 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(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  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1629,7 +1644,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  unsigned countLeadingZeros() const {
+if constexpr (!Signed)
+  return llvm::countl_zero(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 

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 521078.

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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = S.Current->getSource(OpPC);
 S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt();
@@ -125,6 +126,16 @@
 QualType Ty = E->getType();
 S.CCEDiag(E, diag::note_constexpr_large_shift) << Val << Ty << Bits;
 return false;
+  } else 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.
+// C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+// E1 x 2^E2 module 2^N.
+if (LHS.isNegative())
+  S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS.toAPSInt();
+else if (LHS.toUnsigned().countLeadingZeros() < static_cast(RHS))
+  S.CCEDiag(E, diag::note_constexpr_lshift_discards);
   }
   return true;
 }
@@ -1612,7 +1623,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1629,7 +1640,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  unsigned countLeadingZeros() const {
+if constexpr (!Signed)
+  return llvm::countl_zero(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 

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 520954.

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 +152,14 @@
   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}}
+  }
+
 };
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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = S.Current->getSource(OpPC);
 S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt();
@@ -125,6 +126,16 @@
 QualType Ty = E->getType();
 S.CCEDiag(E, diag::note_constexpr_large_shift) << Val << Ty << Bits;
 return false;
+  } else 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.
+// C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+// E1 x 2^E2 module 2^N.
+if (LHS.isNegative())
+  S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS.toAPSInt();
+else if (LHS.toUnsigned().countLeadingZeros() < static_cast(RHS))
+  S.CCEDiag(E, diag::note_constexpr_lshift_discards);
   }
   return true;
 }
@@ -1612,7 +1623,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1629,7 +1640,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  unsigned countLeadingZeros() const {
+if constexpr (!Signed)
+  return llvm::countl_zero(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 +152,14 @@
   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}}
+  }
+
 };
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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = 

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

tbaeder added inline comments.



Comment at: clang/lib/AST/Interp/Interp.h:136
+if (LHS.isNegative())
+  S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << 12;
+else if (LHS.toUnsigned().countLeadingZeros() < static_cast(RHS))

shafik wrote:
> Do we test this diagnostic?
OH! No, and the `12` was just a debug value I forgot to replace with the real 
thing.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150209/new/

https://reviews.llvm.org/D150209

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik added inline comments.



Comment at: clang/lib/AST/Interp/Interp.h:133
+// operand, and must not overflow the corresponding unsigned type.
+// C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+// E1 x 2^E2 module 2^N.

Maybe this quote for C++20 should be moved below the else block with a comment 
noting that C++20 forward the above is no longer UB? My first reading I thought 
the second quote applied to the `else if` below and was super confused.



Comment at: clang/lib/AST/Interp/Interp.h:136
+if (LHS.isNegative())
+  S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << 12;
+else if (LHS.toUnsigned().countLeadingZeros() < static_cast(RHS))

Do we test this diagnostic?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150209/new/

https://reviews.llvm.org/D150209

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D150209: [clang][Interp] Add more shift error checking

[Timm Bäder via Phabricator via cfe-commits]

tbaeder created this revision.
tbaeder added reviewers: aaron.ballman, erichkeane, tahonermann, shafik.
Herald added a project: All.
tbaeder requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Repository:
  rG LLVM Github Monorepo

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 +152,14 @@
   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}}
+  }
+
 };
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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {
+template 
+bool CheckShift(InterpState , CodePtr OpPC, const LT , const RT ,
+unsigned Bits) {
   if (RHS.isNegative()) {
 const SourceInfo  = S.Current->getSource(OpPC);
 S.CCEDiag(Loc, diag::note_constexpr_negative_shift) << RHS.toAPSInt();
@@ -125,6 +126,16 @@
 QualType Ty = E->getType();
 S.CCEDiag(E, diag::note_constexpr_large_shift) << Val << Ty << Bits;
 return false;
+  } else 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.
+// C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
+// E1 x 2^E2 module 2^N.
+if (LHS.isNegative())
+  S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << 12;
+else if (LHS.toUnsigned().countLeadingZeros() < static_cast(RHS))
+  S.CCEDiag(E, diag::note_constexpr_lshift_discards);
   }
   return true;
 }
@@ -1612,7 +1623,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral R;
@@ -1629,7 +1640,7 @@
   const auto  = S.Stk.pop();
   const unsigned Bits = LHS.bitWidth();
 
-  if (!CheckShift(S, OpPC, RHS, Bits))
+  if (!CheckShift(S, OpPC, LHS, RHS, Bits))
 return false;
 
   Integral 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(V); }
+  unsigned countLeadingZeros() const {
+if constexpr (!Signed)
+  return llvm::countl_zero(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 +152,14 @@
   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}}
+  }
+
 };
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 , CodePtr OpPC, const Pointer );
 
 /// Checks if the shift operation is legal.
-template 
-bool CheckShift(InterpState , CodePtr OpPC, const RT , unsigned Bits) {