From e19ee2b50e5bb55fc2a16a7b6bf3131181302b04 Mon Sep 17 00:00:00 2001
From: Sergey Fedorov <barracuda@macos-powerpc.org>
Date: Wed, 29 Jul 2026 07:40:59 +0000
Subject: [PATCH 03/13] folly/DiscriminatedPtr: support 32-bit architectures
 (ppc32)

The tag was stored in bits 48-63 of a uintptr_t.  On 32-bit targets
uintptr_t is 32 bits wide, so the shifts were out of range and the tag
was lost; the header refused 32-bit builds via #error, which broke
building the test suite on Darwin/ppc32.

Store data_ as uint64_t instead: the pointer still occupies the low
bits (all 32 of them on 32-bit targets) and the tag bits 48-63, so the
class now works unchanged on 32-bit.  On 64-bit targets uintptr_t ==
uint64_t, so this is a no-op.  Allow FOLLY_PPC in the arch check.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013G8CDpEyDCCgV4jaMM9WME
---
 folly/DiscriminatedPtr.h | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/folly/DiscriminatedPtr.h b/folly/DiscriminatedPtr.h
index b2125f5a5..8e99e4ff1 100644
--- a/folly/DiscriminatedPtr.h
+++ b/folly/DiscriminatedPtr.h
@@ -33,8 +33,9 @@
 #include <folly/Portability.h>
 #include <folly/detail/DiscriminatedPtrDetail.h>
 
-#if !FOLLY_X64 && !FOLLY_AARCH64 && !FOLLY_PPC64 && !FOLLY_RISCV64
-#error "DiscriminatedPtr is x64, arm64, ppc64 and riscv64 specific code."
+#if !FOLLY_X64 && !FOLLY_AARCH64 && !FOLLY_PPC && !FOLLY_PPC64 && \
+    !FOLLY_RISCV64
+#error "DiscriminatedPtr is x64, arm64, ppc, ppc64 and riscv64 specific code."
 #endif
 
 namespace folly {
@@ -201,13 +202,14 @@ class DiscriminatedPtr {
     return uint16_t(idx + 1);
   }
   void* ptr() const {
-    return reinterpret_cast<void*>(data_ & ((1ULL << 48) - 1));
+    return reinterpret_cast<void*>(
+        static_cast<uintptr_t>(data_ & ((1ULL << 48) - 1)));
   }
 
   void set(void* p, uint16_t v) {
-    uintptr_t ip = reinterpret_cast<uintptr_t>(p);
+    uint64_t ip = reinterpret_cast<uintptr_t>(p);
     CHECK(!(ip >> 48));
-    ip |= static_cast<uintptr_t>(v) << 48;
+    ip |= static_cast<uint64_t>(v) << 48;
     data_ = ip;
   }
 
@@ -215,9 +217,11 @@ class DiscriminatedPtr {
    * We store a pointer in the least significant 48 bits of data_, and a type
    * index (0 = empty, or 1-based index in Types) in the most significant 16
    * bits.  We rely on the fact that pointers have their most significant 16
-   * bits clear on x86_64.
+   * bits clear on x86_64.  data_ is a uint64_t rather than uintptr_t so that
+   * the same layout works on 32-bit architectures, where pointers occupy only
+   * the low 32 bits.
    */
-  uintptr_t data_;
+  uint64_t data_;
 };
 
 template <typename Visitor, typename... Args>
-- 
2.43.0