[hwasan] Remove lazy thread-initialisation

This was an experiment made possible by a non-standard feature of the
Android dynamic loader.

It required introducing a flag to tell the compiler which ABI was being
targeted.
This flag is no longer needed, since the generated code now works for
both ABI's.

We leave that flag untouched for backwards compatibility. This also
means that if we need to distinguish between targeted ABI's again
we can do that without disturbing any existing workflows.

We leave a comment in the source code and mention in the help text to
explain this for any confused person reading the code in the future.

Patch by Matthew Malcomson

Differential Revision: https://reviews.llvm.org/D69574

1 files changed, 2 insertions, 27 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index f87132ee475..697f2f7eec6 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -284,7 +284,6 @@ private:
 
   FunctionCallee HwasanTagMemoryFunc;
   FunctionCallee HwasanGenerateTagFunc;
-  FunctionCallee HwasanThreadEnterFunc;
 
   Constant *ShadowGlobal;
 
@@ -473,9 +472,6 @@ void HWAddressSanitizer::initializeCallbacks(Module &M) {
 
   HWAsanHandleVfork =
       M.getOrInsertFunction("__hwasan_handle_vfork", IRB.getVoidTy(), IntptrTy);
-
-  HwasanThreadEnterFunc =
-      M.getOrInsertFunction("__hwasan_thread_enter", IRB.getVoidTy());
 }
 
 Value *HWAddressSanitizer::getDynamicShadowIfunc(IRBuilder<> &IRB) {
@@ -934,34 +930,13 @@ void HWAddressSanitizer::emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord) {
   Value *SlotPtr = getHwasanThreadSlotPtr(IRB, IntptrTy);
   assert(SlotPtr);
 
-  Instruction *ThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
-
-  Function *F = IRB.GetInsertBlock()->getParent();
-  if (F->getFnAttribute("hwasan-abi").getValueAsString() == "interceptor") {
-    Value *ThreadLongEqZero =
-        IRB.CreateICmpEQ(ThreadLong, ConstantInt::get(IntptrTy, 0));
-    auto *Br = cast<BranchInst>(SplitBlockAndInsertIfThen(
-        ThreadLongEqZero, cast<Instruction>(ThreadLongEqZero)->getNextNode(),
-        false, MDBuilder(*C).createBranchWeights(1, 100000)));
-
-    IRB.SetInsertPoint(Br);
-    // FIXME: This should call a new runtime function with a custom calling
-    // convention to avoid needing to spill all arguments here.
-    IRB.CreateCall(HwasanThreadEnterFunc);
-    LoadInst *ReloadThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
-
-    IRB.SetInsertPoint(&*Br->getSuccessor(0)->begin());
-    PHINode *ThreadLongPhi = IRB.CreatePHI(IntptrTy, 2);
-    ThreadLongPhi->addIncoming(ThreadLong, ThreadLong->getParent());
-    ThreadLongPhi->addIncoming(ReloadThreadLong, ReloadThreadLong->getParent());
-    ThreadLong = ThreadLongPhi;
-  }
-
+  Value *ThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
   // Extract the address field from ThreadLong. Unnecessary on AArch64 with TBI.
   Value *ThreadLongMaybeUntagged =
       TargetTriple.isAArch64() ? ThreadLong : untagPointer(IRB, ThreadLong);
 
   if (WithFrameRecord) {
+    Function *F = IRB.GetInsertBlock()->getParent();
     StackBaseTag = IRB.CreateAShr(ThreadLong, 3);
 
     // Prepare ring buffer data.