8258382: Fix optimization-unstable code involving pointer overflow

src/hotspot/share/gc/parallel/psPromotionLAB.hpp

@@ -118,8 +118,7 @@ class PSOldPromotionLAB : public PSPromotionLAB {
     // assert(_state != flushed, "Sanity");
     assert(_start_array != NULL, "Sanity");
     HeapWord* obj = top();
-    // Pointer overflow check is needed here.
-    if (end() >= obj && size <= (size_t) (end() - obj)) {
+    if (size <= pointer_delta(end(), obj)) {
       HeapWord* new_top = obj + size;
       set_top(new_top);
       assert(is_object_aligned(obj) && is_object_aligned(new_top),

src/hotspot/share/gc/parallel/psPromotionLAB.inline.hpp

@@ -33,8 +33,7 @@ HeapWord* PSYoungPromotionLAB::allocate(size_t size) {
   // Can't assert this, when young fills, we keep the LAB around, but flushed.
   // assert(_state != flushed, "Sanity");
   HeapWord* obj = top();
-  // Pointer overflow check is needed here.
-  if (end() >= obj && size <= (size_t)(end() - obj)) {
+  if (size <= pointer_delta(end(), obj)) {
     HeapWord* new_top = obj + size;
     set_top(new_top);
     assert(is_object_aligned(new_top), "checking alignment");

src/hotspot/share/opto/ifnode.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -631,15 +631,15 @@ const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node* val, Node* if_proj
               return cmp2_t;
             case BoolTest::lt:
               lo = TypeInt::INT->_lo;
-              if (hi != min_jint) {
+              if (hi - 1 < hi) {
                 hi = hi - 1;
               }
               break;
             case BoolTest::le:
               lo = TypeInt::INT->_lo;
               break;
             case BoolTest::gt:
-              if (lo != max_jint) {
+              if (lo + 1 > lo) {
                 lo = lo + 1;
               }
               hi = TypeInt::INT->_hi;

src/hotspot/share/opto/loopTransform.cpp

@@ -912,12 +912,12 @@ bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
       const TypeInt* iv_type = phase->_igvn.type(phi)->is_int();
       int next_stride = stride_con * 2; // stride after this unroll
       if (next_stride > 0) {
-        if (iv_type->_lo > max_jint - next_stride || // overflow
+        if (iv_type->_lo + next_stride <= iv_type->_lo || // overflow
             iv_type->_lo + next_stride >  iv_type->_hi) {
           return false;  // over-unrolling
         }
       } else if (next_stride < 0) {
-        if (iv_type->_hi < min_jint - next_stride || // overflow
+        if (iv_type->_hi + next_stride >= iv_type->_hi || // overflow
             iv_type->_hi + next_stride <  iv_type->_lo) {
           return false;  // over-unrolling
         }
@@ -928,8 +928,8 @@ bool IdealLoopTree::policy_unroll(PhaseIdealLoop *phase) {
   // After unroll limit will be adjusted: new_limit = limit-stride.
   // Bailout if adjustment overflow.
   const TypeInt* limit_type = phase->_igvn.type(limit_n)->is_int();
-  if ((stride_con > 0 && ((min_jint + stride_con) > limit_type->_hi)) ||
-      (stride_con < 0 && ((max_jint + stride_con) < limit_type->_lo)))
+  if ((stride_con > 0 && ((limit_type->_hi - stride_con) >= limit_type->_hi)) ||
+      (stride_con < 0 && ((limit_type->_lo - stride_con) <= limit_type->_lo)))
     return false;  // overflow
 
   // Adjust body_size to determine if we unroll or not

src/hotspot/share/opto/parse2.cpp

@@ -536,7 +536,7 @@ void Parse::do_lookupswitch() {
     }
     prev = match_int+1;
   }
-  if (prev != min_jint) {
+  if (prev-1 != max_jint) {
     defaults += (float)max_jint - prev + 1;
   }
   float default_cnt = 1;