Merge pull request #1383 from donc/ctfe9170reinterpret_float_int

9170 CTFE: Allow reinterpret casts float <-> int

src/ctfe.h

@@ -182,6 +182,12 @@ int comparePointers(Loc loc, enum TOK op, Type *type, Expression *agg1, dinteger
 Expression *pointerArithmetic(Loc loc, enum TOK op, Type *type,
     Expression *eptr, Expression *e2);
 
+// True if conversion from type 'from' to 'to' involves a reinterpret_cast
+// floating point -> integer or integer -> floating point
+bool isFloatIntPaint(Type *to, Type *from);
+
+// Reinterpret float/int value 'fromVal' as a float/integer of type 'to'.
+Expression *paintFloatInt(Expression *fromVal, Type *to);
 
 /// Return true if t is an AA, or AssociativeArray!(key, value)
 bool isAssocArray(Type *t);

src/ctfeexpr.c

@@ -760,6 +760,66 @@ int comparePointers(Loc loc, enum TOK op, Type *type, Expression *agg1, dinteger
     return cmp;
 }
 
+union UnionFloatInt
+{
+    float f;
+    d_int32 x;
+};
+
+union UnionDoubleLong
+{
+    double f;
+    d_int64 x;
+};
+
+// True if conversion from type 'from' to 'to' involves a reinterpret_cast
+// floating point -> integer or integer -> floating point
+bool isFloatIntPaint(Type *to, Type *from)
+{
+    return (from->size() == to->size()) &&
+        (  (from->isintegral() && to->isfloating())
+        || (from->isfloating() && to->isintegral()) );
+}
+
+// Reinterpret float/int value 'fromVal' as a float/integer of type 'to'.
+Expression *paintFloatInt(Expression *fromVal, Type *to)
+{
+    if (exceptionOrCantInterpret(fromVal))
+        return fromVal;
+
+    if (to->size() == 4)
+    {
+        UnionFloatInt u;
+        if (to->isintegral())
+        {
+            u.f = fromVal->toReal();
+            return new IntegerExp(fromVal->loc, u.x, to);
+        }
+        else
+        {
+            u.x = fromVal->toInteger();
+            return new RealExp(fromVal->loc, u.f, to);
+        }
+    }
+    else if (to->size() == 8)
+    {
+        UnionDoubleLong v;
+        if (to->isintegral())
+        {
+            v.f = fromVal->toReal();
+            return new IntegerExp(fromVal->loc, v.x, to);
+        }
+        else
+        {
+            v.x = fromVal->toInteger();
+            return new RealExp(fromVal->loc, v.f, to);
+        }
+    }
+    else
+        assert(0);
+}
+
+
 /***********************************************
       Primitive integer operations
 ***********************************************/

src/interpret.c

@@ -4806,6 +4806,22 @@ Expression *PtrExp::interpret(InterState *istate, CtfeGoal goal)
 #if LOG
     printf("%s PtrExp::interpret() %s\n", loc.toChars(), toChars());
 #endif
+
+    // Check for int<->float and long<->double casts.
+
+    if ( e1->op == TOKsymoff && ((SymOffExp *)e1)->offset == 0
+        && isFloatIntPaint(type, ((SymOffExp *)e1)->var->type) )
+    {   // *(cast(int*)&v, where v is a float variable
+        return paintFloatInt(getVarExp(loc, istate, ((SymOffExp *)e1)->var, ctfeNeedRvalue),
+            type);
+    }
+    else if (e1->op == TOKcast && ((CastExp *)e1)->e1->op == TOKaddress)
+    {   // *(cast(int *))&x   where x is a float expression
+        Expression *x = ((AddrExp *)(((CastExp *)e1)->e1))->e1;
+        if ( isFloatIntPaint(type, x->type) )
+            return paintFloatInt(x->interpret(istate), type);
+    }
+
     // Constant fold *(&structliteral + offset)
     if (e1->op == TOKadd)
     {   AddExp *ae = (AddExp *)e1;

test/compilable/interpret3.d

@@ -3329,6 +3329,56 @@ static assert(!is(typeof(compiles!(badpointer(6)))));
 static assert(!is(typeof(compiles!(badpointer(7)))));
 static assert(!is(typeof(compiles!(badpointer(8)))));
 
+/**************************************************
+    9170 Allow reinterpret casts float<->int
+**************************************************/
+int f9170(float x) {
+    return *(cast(int*)&x);
+}
+
+float i9170(int x) {
+    return *(cast(float*)&x);
+}
+
+float u9170(uint x) {
+    return *(cast(float*)&x);
+}
+
+int f9170arr(float[] x) {
+    return *(cast(int*)&(x[1]));
+}
+
+long d9170(double x) {
+    return *(cast(long*)&x);
+}
+
+int fref9170(ref float x) {
+    return *(cast(int*)&x);
+}
+
+long dref9170(ref double x) {
+    return *(cast(long*)&x);
+}
+
+bool bug9170()
+{
+    float f = 1.25;
+    double d = 1.25;
+    assert(f9170(f) == 0x3FA0_0000);
+    assert(fref9170(f) == 0x3FA0_0000);
+    assert(d9170(d)==0x3FF4_0000_0000_0000L);
+    assert(dref9170(d)==0x3FF4_0000_0000_0000L);
+    float [3] farr = [0, 1.25, 0];
+    assert(f9170arr(farr) == 0x3FA0_0000);
+    int i = 0x3FA0_0000;
+    assert(i9170(i) == 1.25);
+    uint u = 0x3FA0_0000;
+    assert(u9170(u) == 1.25);
+    return true;
+}
+
+static assert(bug9170());
+
 /**************************************************
     6792 ICE with pointer cast of indexed array
 **************************************************/