[asan] poison_heap=0 should not disable __asan_handle_no_return.

compiler-rt/trunk/lib/asan/asan_poisoning.h

void PoisonShadowPartialRightRedzone(uptr addr,
                                      uptr redzone_size,
                                      u8 value);
 
 // Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
 // assume that memory addresses are properly aligned. Use in
 // performance-critical code with care.
 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
                                     u8 value) {
-  DCHECK(CanPoisonMemory());
+  DCHECK(!value || CanPoisonMemory());
   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
   uptr shadow_end = MEM_TO_SHADOW(
       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
   // FIXME: Page states are different on Windows, so using the same interface
   // for mapping shadow and zeroing out pages doesn't "just work", so we should
   // probably provide higher-level interface for these operations.
   // For now, just memset on Windows.
   if (value || SANITIZER_WINDOWS == 1 ||

compiler-rt/trunk/lib/asan/asan_poisoning.cc

void SetCanPoisonMemory(bool value) {
   atomic_store(&can_poison_memory, value, memory_order_release);
 }
 
 bool CanPoisonMemory() {
   return atomic_load(&can_poison_memory, memory_order_acquire);
 }
 
 void PoisonShadow(uptr addr, uptr size, u8 value) {
-  if (!CanPoisonMemory()) return;
+  if (value && !CanPoisonMemory()) return;
   CHECK(AddrIsAlignedByGranularity(addr));
   CHECK(AddrIsInMem(addr));
   CHECK(AddrIsAlignedByGranularity(addr + size));
   CHECK(AddrIsInMem(addr + size - SHADOW_GRANULARITY));
   CHECK(REAL(memset));
   FastPoisonShadow(addr, size, value);
 }
 

compiler-rt/trunk/test/asan/TestCases/handle_noreturn_bug.cc

+// Regression test: __asan_handle_no_return should unpoison stack even with poison_heap=0.
+// RUN: %clangxx_asan -O0 %s -o %t && \
+// RUN: %env_asan_opts=poison_heap=1 %run %t && \
+// RUN: %env_asan_opts=poison_heap=0 %run %t
+
+#include <sanitizer/asan_interface.h>
+
+int main(int argc, char **argv) {
+  int x[2];
+  int * volatile p = &x[0];
+  __asan_handle_no_return();
+  int volatile z = p[2];
+}