diff --git a/compiler-rt/lib/asan/asan_allocator.h b/compiler-rt/lib/asan/asan_allocator.h
index db8dc3bebfc62..6fb533423580d 100644
--- a/compiler-rt/lib/asan/asan_allocator.h
+++ b/compiler-rt/lib/asan/asan_allocator.h
@@ -197,7 +197,11 @@ const uptr kAllocatorSpace = ~(uptr)0;
 #    endif  // SANITIZER_APPLE
 
 #    if defined(__powerpc64__)
+#      if SANITIZER_AIX
+const uptr kAllocatorSize = 1ULL << 38;  // 256G.
+#      else
 const uptr kAllocatorSize  =  0x20000000000ULL;  // 2T.
+#      endif
 typedef DefaultSizeClassMap SizeClassMap;
 #    elif defined(__aarch64__) && SANITIZER_ANDROID
 // Android needs to support 39, 42 and 48 bit VMA.
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h
index 62523c7ae187c..e5b912d70e61e 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_internal.h
@@ -23,7 +23,12 @@ namespace __sanitizer {
 typedef CompactSizeClassMap InternalSizeClassMap;
 
 struct AP32 {
+// For AIX 64-bit, the mmap begin is at address 0x0a00000000000000ULL.
+#if SANITIZER_AIX && SANITIZER_WORDSIZE == 64
+  static const uptr kSpaceBeg = 0x0a00000000000000ULL;
+#else
   static const uptr kSpaceBeg = 0;
+#endif
   static const u64 kSpaceSize = SANITIZER_MMAP_RANGE_SIZE;
   static const uptr kMetadataSize = 0;
   typedef InternalSizeClassMap SizeClassMap;
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary32.h b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary32.h
index 602b197c42ae3..0faf9b3c151a4 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary32.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary32.h
@@ -288,6 +288,7 @@ class SizeClassAllocator32 {
   uptr ComputeRegionId(uptr mem) const {
     if (SANITIZER_SIGN_EXTENDED_ADDRESSES)
       mem &= (kSpaceSize - 1);
+    mem -= kSpaceBeg;
     const uptr res = mem >> kRegionSizeLog;
     CHECK_LT(res, kNumPossibleRegions);
     return res;