[SanitizerCoverage] Optimize stack-depth instrumentation.

Summary:
Use the initialexec TLS type and eliminate calls to the TLS
wrapper.  Fixes the sanitizer-x86_64-linux-fuzzer bot failure.

Reviewers: vitalybuka, kcc

Reviewed By: kcc

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D37026

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311490 91177308-0d34-0410-b5e6-96231b3b80d8

Author: morehouse

lib/Transforms/Instrumentation/SanitizerCoverage.cpp

@@ -77,8 +77,6 @@ static const char *const SanCovCountersSectionName = "sancov_cntrs";
 static const char *const SanCovPCsSectionName = "sancov_pcs";
 
 static const char *const SanCovLowestStackName = "__sancov_lowest_stack";
-static const char *const SanCovLowestStackTLSWrapperName =
-    "_ZTW21__sancov_lowest_stack";
 
 static cl::opt<int> ClCoverageLevel(
     "sanitizer-coverage-level",
@@ -229,7 +227,6 @@ class SanitizerCoverageModule : public ModulePass {
   Function *SanCovTraceDivFunction[2];
   Function *SanCovTraceGepFunction;
   Function *SanCovTraceSwitchFunction;
-  Function *SanCovLowestStackTLSWrapper;
   GlobalVariable *SanCovLowestStack;
   InlineAsm *EmptyAsm;
   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy,
@@ -351,20 +348,11 @@ bool SanitizerCoverageModule::runOnModule(Module &M) {
 
   Constant *SanCovLowestStackConstant =
       M.getOrInsertGlobal(SanCovLowestStackName, IntptrTy);
-  SanCovLowestStackTLSWrapper =
-      checkSanitizerInterfaceFunction(M.getOrInsertFunction(
-          SanCovLowestStackTLSWrapperName, IntptrTy->getPointerTo()));
-  if (Options.StackDepth) {
-    assert(isa<GlobalVariable>(SanCovLowestStackConstant));
-    SanCovLowestStack = cast<GlobalVariable>(SanCovLowestStackConstant);
-    if (!SanCovLowestStack->isDeclaration()) {
-      // Check that the user has correctly defined:
-      //     thread_local uintptr_t __sancov_lowest_stack
-      // and initialize it.
-      assert(SanCovLowestStack->isThreadLocal());
-      SanCovLowestStack->setInitializer(Constant::getAllOnesValue(IntptrTy));
-    }
-  }
+  SanCovLowestStack = cast<GlobalVariable>(SanCovLowestStackConstant);
+  SanCovLowestStack->setThreadLocalMode(
+      GlobalValue::ThreadLocalMode::InitialExecTLSModel);
+  if (Options.StackDepth && !SanCovLowestStack->isDeclaration())
+    SanCovLowestStack->setInitializer(Constant::getAllOnesValue(IntptrTy));
 
   // Make sure smaller parameters are zero-extended to i64 as required by the
   // x86_64 ABI.
@@ -484,9 +472,6 @@ bool SanitizerCoverageModule::runOnFunction(Function &F) {
   if (F.getName() == "__local_stdio_printf_options" ||
       F.getName() == "__local_stdio_scanf_options")
     return false;
-  // Avoid infinite recursion by not instrumenting stack depth TLS wrapper
-  if (F.getName() == SanCovLowestStackTLSWrapperName)
-    return false;
   // Don't instrument functions using SEH for now. Splitting basic blocks like
   // we do for coverage breaks WinEHPrepare.
   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
@@ -771,12 +756,11 @@ void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
     auto FrameAddrPtr =
         IRB.CreateCall(GetFrameAddr, {Constant::getNullValue(Int32Ty)});
     auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
-    auto LowestStackPtr = IRB.CreateCall(SanCovLowestStackTLSWrapper);
-    auto LowestStack = IRB.CreateLoad(LowestStackPtr);
+    auto LowestStack = IRB.CreateLoad(SanCovLowestStack);
     auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
     auto ThenTerm = SplitBlockAndInsertIfThen(IsStackLower, &*IP, false);
     IRBuilder<> ThenIRB(ThenTerm);
-    ThenIRB.CreateStore(FrameAddrInt, LowestStackPtr);
+    ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
   }
 }
 

test/Instrumentation/SanitizerCoverage/stack-depth.ll

@@ -8,20 +8,19 @@
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
-; CHECK: @__sancov_lowest_stack = thread_local global i64 -1
+; CHECK: @__sancov_lowest_stack = thread_local(initialexec) global i64 -1
 @__sancov_lowest_stack = thread_local global i64 0, align 8
 
 define i32 @foo() {
 entry:
 ; CHECK-LABEL: define i32 @foo
 ; CHECK: [[framePtr:%[^ \t]+]] = call i8* @llvm.frameaddress(i32 0)
 ; CHECK: [[frameInt:%[^ \t]+]] = ptrtoint i8* [[framePtr]] to [[$intType:i[0-9]+]]
-; CHECK: [[lowestPtr:%[^ \t]+]] = call [[$intType]]* @_ZTW21__sancov_lowest_stack
-; CHECK: [[lowestInt:%[^ \t]+]] = load [[$intType]], [[$intType]]* [[lowestPtr]]
-; CHECK: [[cmp:%[^ \t]+]] = icmp ult [[$intType]] [[frameInt]], [[lowestInt]]
+; CHECK: [[lowest:%[^ \t]+]] = load [[$intType]], [[$intType]]* @__sancov_lowest_stack
+; CHECK: [[cmp:%[^ \t]+]] = icmp ult [[$intType]] [[frameInt]], [[lowest]]
 ; CHECK: br i1 [[cmp]], label %[[ifLabel:[^ \t]+]], label
 ; CHECK: <label>:[[ifLabel]]:
-; CHECK: store [[$intType]] [[frameInt]], [[$intType]]* [[lowestPtr]]
+; CHECK: store [[$intType]] [[frameInt]], [[$intType]]* @__sancov_lowest_stack
 ; CHECK: ret i32 7
 
   ret i32 7
@@ -32,12 +31,11 @@ entry:
 ; CHECK-LABEL: define i32 @bar
 ; CHECK: [[framePtr:%[^ \t]+]] = call i8* @llvm.frameaddress(i32 0)
 ; CHECK: [[frameInt:%[^ \t]+]] = ptrtoint i8* [[framePtr]] to [[$intType]]
-; CHECK: [[lowestPtr:%[^ \t]+]] = call [[$intType]]* @_ZTW21__sancov_lowest_stack
-; CHECK: [[lowestInt:%[^ \t]+]] = load [[$intType]], [[$intType]]* [[lowestPtr]]
-; CHECK: [[cmp:%[^ \t]+]] = icmp ult [[$intType]] [[frameInt]], [[lowestInt]]
+; CHECK: [[lowest:%[^ \t]+]] = load [[$intType]], [[$intType]]* @__sancov_lowest_stack
+; CHECK: [[cmp:%[^ \t]+]] = icmp ult [[$intType]] [[frameInt]], [[lowest]]
 ; CHECK: br i1 [[cmp]], label %[[ifLabel:[^ \t]+]], label
 ; CHECK: <label>:[[ifLabel]]:
-; CHECK: store [[$intType]] [[frameInt]], [[$intType]]* [[lowestPtr]]
+; CHECK: store [[$intType]] [[frameInt]], [[$intType]]* @__sancov_lowest_stack
 ; CHECK: %call = call i32 @foo()
 ; CHECK: ret i32 %call