Split interesting warnings off from -Wfloat-conversion

Restructure the implict floating point to integer conversions so that
interesting sub-groups are under different flags.  Breakdown of warnings:

No warning:
Exact conversions from floating point to integer:
int x = 10.0;
int x = 1e10;

-Wliteral-conversion - Floating point literal to integer with rounding:
int x = 5.5;
int x = -3.4;

-Wfloat-conversion - All conversions not covered by the above two:
int x = GetFloat();
int x = 5.5 + 3.5;

-Wfloat-zero-conversion - The expression converted has a non-zero floating
point value that gets converted to a zero integer value, excluded the cases
falling under -Wliteral-conversion.  Subset of -Wfloat-conversion.
int x = 1.0 / 2.0;

-Wfloat-overflow-conversion - The floating point value is outside the range
of the integer type, exluding cases from -Wliteral conversion.  Subset of
-Wfloat-conversion.
char x = 500;
char x = -1000;

-Wfloat-bool-conversion - Any conversion of a floating point type to bool.
Subset of -Wfloat-conversion.
if (GetFloat()) {}
bool x = 5.0;

-Wfloat-bool-constant-conversion - Conversion of a compile time evaluatable
floating point value to bool.  Subset of -Wfloat-bool-conversion.
bool x = 1.0;
bool x = 4.0 / 20.0;

Also add EvaluateAsFloat to Sema, which is similar to EvaluateAsInt, but for
floating point values.

llvm-svn: 267054

1 files changed, 84 insertions, 27 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index b1e6b99ce48..0592a830113 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -7382,19 +7382,78 @@ void DiagnoseImpCast(Sema &S, Expr *E, QualType T, SourceLocation CContext,
   DiagnoseImpCast(S, E, E->getType(), T, CContext, diag, pruneControlFlow);
 }
 
-/// Diagnose an implicit cast from a literal expression. Does not warn when the
-/// cast wouldn't lose information.
-void DiagnoseFloatingLiteralImpCast(Sema &S, FloatingLiteral *FL, QualType T,
-                                    SourceLocation CContext) {
-  // Try to convert the literal exactly to an integer. If we can, don't warn.
+
+/// Diagnose an implicit cast from a floating point value to an integer value.
+void DiagnoseFloatingImpCast(Sema &S, Expr *E, QualType T,
+
+                             SourceLocation CContext) {
+  const bool IsBool = T->isSpecificBuiltinType(BuiltinType::Bool);
+  const bool PruneWarnings = !S.ActiveTemplateInstantiations.empty();
+
+  Expr *InnerE = E->IgnoreParenImpCasts();
+  // We also want to warn on, e.g., "int i = -1.234"
+  if (UnaryOperator *UOp = dyn_cast<UnaryOperator>(InnerE))
+    if (UOp->getOpcode() == UO_Minus || UOp->getOpcode() == UO_Plus)
+      InnerE = UOp->getSubExpr()->IgnoreParenImpCasts();
+
+  const bool IsLiteral =
+      isa<FloatingLiteral>(E) || isa<FloatingLiteral>(InnerE);
+
+  llvm::APFloat Value(0.0);
+  bool IsConstant =
+    E->EvaluateAsFloat(Value, S.Context, Expr::SE_AllowSideEffects);
+  if (!IsConstant) {
+    if (IsBool) {
+      return DiagnoseImpCast(S, E, T, CContext, diag::warn_impcast_float_bool,
+                             PruneWarnings);
+    } else {
+      return DiagnoseImpCast(S, E, T, CContext,
+                             diag::warn_impcast_float_integer, PruneWarnings);
+    }
+  }
+
   bool isExact = false;
-  const llvm::APFloat &Value = FL->getValue();
+
   llvm::APSInt IntegerValue(S.Context.getIntWidth(T),
                             T->hasUnsignedIntegerRepresentation());
-  if (Value.convertToInteger(IntegerValue,
-                             llvm::APFloat::rmTowardZero, &isExact)
-      == llvm::APFloat::opOK && isExact)
-    return;
+  if (Value.convertToInteger(IntegerValue, llvm::APFloat::rmTowardZero,
+                             &isExact) == llvm::APFloat::opOK &&
+      isExact && !IsBool) {
+    if (IsLiteral) return;
+    return DiagnoseImpCast(S, E, T, CContext, diag::warn_impcast_float_integer,
+                           PruneWarnings);
+  }
+
+  unsigned DiagID = 0;
+  if (IsBool) {
+    // Warn on all floating point to bool conversions
+    DiagID = diag::warn_impcast_float_to_bool;
+  } else if (IsLiteral) {
+    // Warn on floating point literal to integer.
+    DiagID = diag::warn_impcast_literal_float_to_integer;
+  } else if (IntegerValue == 0) {
+    if (Value.isZero()) {  // Skip -0.0 to 0 conversion.
+      return DiagnoseImpCast(S, E, T, CContext,
+                             diag::warn_impcast_float_integer, PruneWarnings);
+    }
+    // Warn on non-zero to zero conversion.
+    DiagID = diag::warn_impcast_float_to_integer_zero;
+  } else {
+    if (IntegerValue.isUnsigned()) {
+      if (!IntegerValue.isMaxValue()) {
+        return DiagnoseImpCast(S, E, T, CContext,
+                               diag::warn_impcast_float_integer, PruneWarnings);
+      }
+    } else {  // IntegerValue.isSigned()
+      if (!IntegerValue.isMaxSignedValue() &&
+          !IntegerValue.isMinSignedValue()) {
+        return DiagnoseImpCast(S, E, T, CContext,
+                               diag::warn_impcast_float_integer, PruneWarnings);
+      }
+    }
+    // Warn on evaluatable floating point expression to integer conversion.
+    DiagID = diag::warn_impcast_float_to_integer;
+  }
 
   // FIXME: Force the precision of the source value down so we don't print
   // digits which are usually useless (we don't really care here if we
@@ -7407,14 +7466,22 @@ void DiagnoseFloatingLiteralImpCast(Sema &S, FloatingLiteral *FL, QualType T,
   Value.toString(PrettySourceValue, precision);
 
   SmallString<16> PrettyTargetValue;
-  if (T->isSpecificBuiltinType(BuiltinType::Bool))
+  if (IsBool)
     PrettyTargetValue = Value.isZero() ? "false" : "true";
   else
     IntegerValue.toString(PrettyTargetValue);
 
-  S.Diag(FL->getExprLoc(), diag::warn_impcast_literal_float_to_integer)
-    << FL->getType() << T.getUnqualifiedType() << PrettySourceValue
-    << PrettyTargetValue << FL->getSourceRange() << SourceRange(CContext);
+  if (PruneWarnings) {
+    S.DiagRuntimeBehavior(E->getExprLoc(), E,
+                          S.PDiag(DiagID)
+                              << E->getType() << T.getUnqualifiedType()
+                              << PrettySourceValue << PrettyTargetValue
+                              << E->getSourceRange() << SourceRange(CContext));
+  } else {
+    S.Diag(E->getExprLoc(), DiagID)
+        << E->getType() << T.getUnqualifiedType() << PrettySourceValue
+        << PrettyTargetValue << E->getSourceRange() << SourceRange(CContext);
+  }
 }
 
 std::string PrettyPrintInRange(const llvm::APSInt &Value, IntRange Range) {
@@ -7748,22 +7815,12 @@ void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
       return;
     }
 
-    // If the target is integral, always warn.    
+    // If the target is integral, always warn.
     if (TargetBT && TargetBT->isInteger()) {
       if (S.SourceMgr.isInSystemMacro(CC))
         return;
-      
-      Expr *InnerE = E->IgnoreParenImpCasts();
-      // We also want to warn on, e.g., "int i = -1.234"
-      if (UnaryOperator *UOp = dyn_cast<UnaryOperator>(InnerE))
-        if (UOp->getOpcode() == UO_Minus || UOp->getOpcode() == UO_Plus)
-          InnerE = UOp->getSubExpr()->IgnoreParenImpCasts();
-
-      if (FloatingLiteral *FL = dyn_cast<FloatingLiteral>(InnerE)) {
-        DiagnoseFloatingLiteralImpCast(S, FL, T, CC);
-      } else {
-        DiagnoseImpCast(S, E, T, CC, diag::warn_impcast_float_integer);
-      }
+
+      DiagnoseFloatingImpCast(S, E, T, CC);
     }
 
     // Detect the case where a call result is converted from floating-point to