[NFC] [HWASan] make getAndroidSlotPtr function generic (#86200)

This is so we can use a different slot for stack MTE.

Author: fmayer

llvm/include/llvm/Transforms/Utils/MemoryTaggingSupport.h

@@ -84,7 +84,7 @@ bool isLifetimeIntrinsic(Value *V);
 Value *readRegister(IRBuilder<> &IRB, StringRef Name);
 Value *getFP(IRBuilder<> &IRB);
 Value *getPC(const Triple &TargetTriple, IRBuilder<> &IRB);
-Value *getAndroidSanitizerSlotPtr(IRBuilder<> &IRB);
+Value *getAndroidSlotPtr(IRBuilder<> &IRB, int Slot);
 
 } // namespace memtag
 } // namespace llvm

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

@@ -1222,8 +1222,11 @@ Value *HWAddressSanitizer::untagPointer(IRBuilder<> &IRB, Value *PtrLong) {
 }
 
 Value *HWAddressSanitizer::getHwasanThreadSlotPtr(IRBuilder<> &IRB) {
+  // Android provides a fixed TLS slot for sanitizers. See TLS_SLOT_SANITIZER
+  // in Bionic's libc/platform/bionic/tls_defines.h.
+  constexpr int SanitizerSlot = 6;
   if (TargetTriple.isAArch64() && TargetTriple.isAndroid())
-    return memtag::getAndroidSanitizerSlotPtr(IRB);
+    return memtag::getAndroidSlotPtr(IRB, SanitizerSlot);
   return ThreadPtrGlobal;
 }
 

llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp

@@ -273,14 +273,14 @@ Value *getFP(IRBuilder<> &IRB) {
       IRB.getIntPtrTy(M->getDataLayout()));
 }
 
-Value *getAndroidSanitizerSlotPtr(IRBuilder<> &IRB) {
+Value *getAndroidSlotPtr(IRBuilder<> &IRB, int Slot) {
   Module *M = IRB.GetInsertBlock()->getParent()->getParent();
   // Android provides a fixed TLS slot for sanitizers. See TLS_SLOT_SANITIZER
   // in Bionic's libc/private/bionic_tls.h.
   Function *ThreadPointerFunc =
       Intrinsic::getDeclaration(M, Intrinsic::thread_pointer);
   return IRB.CreateConstGEP1_32(IRB.getInt8Ty(),
-                                IRB.CreateCall(ThreadPointerFunc), 0x30);
+                                IRB.CreateCall(ThreadPointerFunc), 8 * Slot);
 }
 
 } // namespace memtag