[clang][Interp] Load result of pre-inc/dec operation if necessary

This can happen in C.

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -3211,15 +3211,20 @@ bool ByteCodeExprGen<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
         return false;
       if (!this->emitAddf(getRoundingMode(E), E))
         return false;
-      return this->emitStoreFloat(E);
+      if (!this->emitStoreFloat(E))
+        return false;
+    } else {
+      assert(isIntegralType(*T));
+      if (!this->emitLoad(*T, E))
+        return false;
+      if (!this->emitConst(1, E))
+        return false;
+      if (!this->emitAdd(*T, E))
+        return false;
+      if (!this->emitStore(*T, E))
+        return false;
     }
-    if (!this->emitLoad(*T, E))
-      return false;
-    if (!this->emitConst(1, E))
-      return false;
-    if (!this->emitAdd(*T, E))
-      return false;
-    return this->emitStore(*T, E);
+    return E->isGLValue() || this->emitLoadPop(*T, E);
   }
   case UO_PreDec: { // --x
     if (!this->visit(SubExpr))
@@ -3250,15 +3255,20 @@ bool ByteCodeExprGen<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
         return false;
       if (!this->emitSubf(getRoundingMode(E), E))
         return false;
-      return this->emitStoreFloat(E);
+      if (!this->emitStoreFloat(E))
+        return false;
+    } else {
+      assert(isIntegralType(*T));
+      if (!this->emitLoad(*T, E))
+        return false;
+      if (!this->emitConst(1, E))
+        return false;
+      if (!this->emitSub(*T, E))
+        return false;
+      if (!this->emitStore(*T, E))
+        return false;
     }
-    if (!this->emitLoad(*T, E))
-      return false;
-    if (!this->emitConst(1, E))
-      return false;
-    if (!this->emitSub(*T, E))
-      return false;
-    return this->emitStore(*T, E);
+    return E->isGLValue() || this->emitLoadPop(*T, E);
   }
   case UO_LNot: // !x
     if (DiscardResult)

clang/test/AST/Interp/c.c

@@ -233,3 +233,15 @@ _Static_assert(funcp == (void*)0, ""); // all-error {{failed due to requirement
                                        // pedantic-warning {{expression is not an integer constant expression}}
 _Static_assert(funcp == (void*)123, ""); // pedantic-warning {{equality comparison between function pointer and void pointer}} \
                                          // pedantic-warning {{expression is not an integer constant expression}}
+
+void unaryops(void) {
+  (void)(++(struct x {unsigned x;}){3}.x);
+  (void)(--(struct y {unsigned x;}){3}.x);
+  (void)(++(struct z {float x;}){3}.x);
+  (void)(--(struct w {float x;}){3}.x);
+
+  (void)((struct xx {unsigned x;}){3}.x++);
+  (void)((struct yy {unsigned x;}){3}.x--);
+  (void)((struct zz {float x;}){3}.x++);
+  (void)((struct ww {float x;}){3}.x--);
+}