tsan: reset destination range in Java heap move

[dvyukov]

Summary

Switch Java heap move to the new scheme required for the new tsan runtime.
Instead of copying the shadow we reset the destination range.
The new v3 trace contains addresses of accesses, so we cannot simply copy the shadow.
This can lead to false negatives, but cannot lead to false positives.

Depends on D110159.

[vitalybuka]

compiler-rt/lib/tsan/rtl/tsan_interface_java.cpp

136

internal_memset?

[dvyukov]

change for loop to internal_memset

compiler-rt/lib/tsan/rtl/tsan_interface_java.cpp

void __tsan_java_move(jptr src, jptr dst, jptr size) {
   DCHECK_LE(dst + size, jctx->heap_begin + jctx->heap_size);
   DCHECK_NE(dst, src);
   DCHECK_NE(size, 0);
 
   // Assuming it's not running concurrently with threads that do
   // memory accesses and mutex operations (stop-the-world phase).
   ctx->metamap.MoveMemory(src, dst, size);
 
-  // Move shadow.
-  RawShadow *s = MemToShadow(src);
+  // Clear the destination shadow range.
+  // We used to move shadow from src to dst, but the trace format does not
+  // support that anymore as it contains addresses of accesses.
   RawShadow *d = MemToShadow(dst);
-  RawShadow *send = MemToShadow(src + size);
-  uptr inc = 1;
-  if (dst > src) {
-    s = MemToShadow(src + size) - 1;
-    d = MemToShadow(dst + size) - 1;
-    send = MemToShadow(src) - 1;
-    inc = -1;
-  }
-  for (; s != send; s += inc, d += inc) {
-    *d = *s;
-    *s = 0;
-  }
+  RawShadow *dend = MemToShadow(dst + size);
+  internal_memset(d, 0, (dend - d) * sizeof(*d));
 }
 
 jptr __tsan_java_find(jptr *from_ptr, jptr to) {
   JAVA_FUNC_ENTER(__tsan_java_find);
   DPrintf("#%d: java_find(&0x%zx, 0x%zx)\n", thr->tid, *from_ptr, to);
   DCHECK_EQ((*from_ptr) % kHeapAlignment, 0);
   DCHECK_EQ(to % kHeapAlignment, 0);
   DCHECK_GE(*from_ptr, jctx->heap_begin);

compiler-rt/test/tsan/java_move_overlap_race.cpp

 // RUN: %clangxx_tsan -O1 %s -o %t
-// RUN: %deflake %run %t 2>&1 | FileCheck %s
-// RUN: %deflake %run %t arg 2>&1 | FileCheck %s
+// RUN: %run %t 2>&1 | FileCheck %s
+// RUN: %run %t arg 2>&1 | FileCheck %s
 #include "java.h"
 
 jptr varaddr1_old;
 jptr varaddr2_old;
 jptr varaddr1_new;
 jptr varaddr2_new;
 
 void *Thread(void *p) {
int main(int argc, char **argv) {
   __tsan_java_move(varaddr1_old, varaddr1_new, kBlockSize);
   barrier_wait(&barrier);
   pthread_join(th, 0);
   __tsan_java_free(varaddr1_new, kBlockSize);
   fprintf(stderr, "DONE\n");
   return __tsan_java_fini();
 }
 
-// CHECK: WARNING: ThreadSanitizer: data race
-// CHECK: WARNING: ThreadSanitizer: data race
+// Note: there is a race on the moved object (which we used to detect),
+// but now __tsan_java_move resets the object shadow, so we don't detect it anymore.
+// CHECK-NOT: WARNING: ThreadSanitizer: data race
 // CHECK: DONE

compiler-rt/test/tsan/java_race_move.cpp

-// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
+// RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
 #include "java.h"
 
 jptr varaddr;
 jptr varaddr2;
 
 void *Thread(void *p) {
   barrier_wait(&barrier);
   *(int*)varaddr2 = 42;
int main() {
   __tsan_java_move(varaddr, varaddr2, kBlockSize);
   barrier_wait(&barrier);
   pthread_join(th, 0);
   __tsan_java_free(varaddr2, kBlockSize);
   fprintf(stderr, "DONE\n");
   return __tsan_java_fini();
 }
 
-// CHECK: WARNING: ThreadSanitizer: data race
+// Note: there is a race on the moved object (which we used to detect),
+// but now __tsan_java_move resets the object shadow, so we don't detect it anymore.
+// CHECK-NOT: WARNING: ThreadSanitizer: data race
 // CHECK: DONE