Track in the AST whether the operand to a UnaryOperator can overflow and then use that logic when evaluating constant expressions and emitting codegen.

llvm-svn: 322074

3 files changed, 27 insertions, 29 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index c46215067a6..668c572942f 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -162,13 +162,13 @@ static bool CanElideOverflowCheck(const ASTContext &Ctx, const BinOpInfo &Op) {
   // we can elide the overflow check.
   if (!Op.mayHaveIntegerOverflow())
     return true;
-
-  // If a unary op has a widened operand, the op cannot overflow.
-  if (const auto *UO = dyn_cast<UnaryOperator>(Op.E))
-    return IsWidenedIntegerOp(Ctx, UO->getSubExpr());
-
-  // We usually don't need overflow checks for binops with widened operands.
-  // Multiplication with promoted unsigned operands is a special case.
+

+  // If a unary op has a widened operand, the op cannot overflow.

+  if (const auto *UO = dyn_cast<UnaryOperator>(Op.E))

+    return !UO->canOverflow();

+

+  // We usually don't need overflow checks for binops with widened operands.

+  // Multiplication with promoted unsigned operands is a special case.

   const auto *BO = cast<BinaryOperator>(Op.E);
   auto OptionalLHSTy = getUnwidenedIntegerType(Ctx, BO->getLHS());
   if (!OptionalLHSTy)
@@ -1870,13 +1870,13 @@ llvm::Value *ScalarExprEmitter::EmitIncDecConsiderOverflowBehavior(
     return Builder.CreateAdd(InVal, Amount, Name);
   case LangOptions::SOB_Undefined:
     if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
-      return Builder.CreateNSWAdd(InVal, Amount, Name);
-    // Fall through.
-  case LangOptions::SOB_Trapping:
-    if (IsWidenedIntegerOp(CGF.getContext(), E->getSubExpr()))
-      return Builder.CreateNSWAdd(InVal, Amount, Name);
-    return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
-  }
+      return Builder.CreateNSWAdd(InVal, Amount, Name);

+    // Fall through.

+  case LangOptions::SOB_Trapping:

+    if (!E->canOverflow())

+      return Builder.CreateNSWAdd(InVal, Amount, Name);

+    return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));

+  }

   llvm_unreachable("Unknown SignedOverflowBehaviorTy");
 }
 
@@ -1952,17 +1952,15 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
     value = Builder.getTrue();
 
   // Most common case by far: integer increment.
-  } else if (type->isIntegerType()) {
-    // Note that signed integer inc/dec with width less than int can't
-    // overflow because of promotion rules; we're just eliding a few steps here.
-    bool CanOverflow = value->getType()->getIntegerBitWidth() >=
-                       CGF.IntTy->getIntegerBitWidth();
-    if (CanOverflow && type->isSignedIntegerOrEnumerationType()) {
-      value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
-    } else if (CanOverflow && type->isUnsignedIntegerType() &&
-               CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
-      value =
-          EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
+  } else if (type->isIntegerType()) {

+    // Note that signed integer inc/dec with width less than int can't

+    // overflow because of promotion rules; we're just eliding a few steps here.

+    if (E->canOverflow() && type->isSignedIntegerOrEnumerationType()) {

+      value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);

+    } else if (E->canOverflow() && type->isUnsignedIntegerType() &&

+               CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {

+      value =

+          EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));

     } else {
       llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
       value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");
diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index f26263d9472..894d0d5fe2f 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -3268,12 +3268,12 @@ CodeGenFunction::GenerateObjCAtomicSetterCopyHelperFunction(
   DeclRefExpr DstExpr(&DstDecl, false, DestTy,
                       VK_RValue, SourceLocation());
   UnaryOperator DST(&DstExpr, UO_Deref, DestTy->getPointeeType(),
-                    VK_LValue, OK_Ordinary, SourceLocation());
+                    VK_LValue, OK_Ordinary, SourceLocation(), false);
   
   DeclRefExpr SrcExpr(&SrcDecl, false, SrcTy,
                       VK_RValue, SourceLocation());
   UnaryOperator SRC(&SrcExpr, UO_Deref, SrcTy->getPointeeType(),
-                    VK_LValue, OK_Ordinary, SourceLocation());
+                    VK_LValue, OK_Ordinary, SourceLocation(), false);
   
   Expr *Args[2] = { &DST, &SRC };
   CallExpr *CalleeExp = cast<CallExpr>(PID->getSetterCXXAssignment());
@@ -3351,7 +3351,7 @@ CodeGenFunction::GenerateObjCAtomicGetterCopyHelperFunction(
                       VK_RValue, SourceLocation());
   
   UnaryOperator SRC(&SrcExpr, UO_Deref, SrcTy->getPointeeType(),
-                    VK_LValue, OK_Ordinary, SourceLocation());
+                    VK_LValue, OK_Ordinary, SourceLocation(), false);
   
   CXXConstructExpr *CXXConstExpr = 
     cast<CXXConstructExpr>(PID->getGetterCXXConstructor());
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 07c1e3aa515..7221ad95b66 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -2483,7 +2483,7 @@ void CodeGenFunction::EmitSections(const OMPExecutableDirective &S) {
                         OK_Ordinary, S.getLocStart(), FPOptions());
     // Increment for loop counter.
     UnaryOperator Inc(&IVRefExpr, UO_PreInc, KmpInt32Ty, VK_RValue, OK_Ordinary,
-                      S.getLocStart());
+                      S.getLocStart(), true);
     auto BodyGen = [Stmt, CS, &S, &IV](CodeGenFunction &CGF) {
       // Iterate through all sections and emit a switch construct:
       // switch (IV) {