hwasan: Enable -hwasan-allow-ifunc by default.

[pcc]

Summary

It's been on in Android for a while without causing problems, so it's time
to make it the default and remove the flag.

[eugenis]

LGTM

compiler-rt/test/hwasan/lit.cfg

 # -*- Python -*-
 
 import os
 
 # Setup config name.
 config.name = 'HWAddressSanitizer' + getattr(config, 'name_suffix', 'default')
 
 # Setup source root.
 config.test_source_root = os.path.dirname(__file__)
 
 # Setup default compiler flags used with -fsanitize=memory option.
 clang_cflags = [config.target_cflags] + config.debug_info_flags
 clang_cxxflags = config.cxx_mode_flags + clang_cflags
-clang_hwasan_cflags = ["-fsanitize=hwaddress", "-mllvm", "-hwasan-generate-tags-with-calls",
-                       "-mllvm", "-hwasan-allow-ifunc"] + clang_cflags
+clang_hwasan_cflags = ["-fsanitize=hwaddress", "-mllvm", "-hwasan-generate-tags-with-calls"] + clang_cflags
 clang_hwasan_cxxflags = config.cxx_mode_flags + clang_hwasan_cflags
 
 def build_invocation(compile_flags):
   return " " + " ".join([config.clang] + compile_flags) + " "
 
 config.substitutions.append( ("%clangxx ", build_invocation(clang_cxxflags)) )
 config.substitutions.append( ("%clang_hwasan ", build_invocation(clang_hwasan_cflags)) )
 config.substitutions.append( ("%clangxx_hwasan ", build_invocation(clang_hwasan_cxxflags)) )

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

static cl::opt<bool>
     ClInstrumentMemIntrinsics("hwasan-instrument-mem-intrinsics",
                               cl::desc("instrument memory intrinsics"),
                               cl::Hidden, cl::init(true));
 
 static cl::opt<bool> ClInlineAllChecks("hwasan-inline-all-checks",
                                        cl::desc("inline all checks"),
                                        cl::Hidden, cl::init(false));
 
-static cl::opt<bool> ClAllowIfunc("hwasan-allow-ifunc",
-                                  cl::desc("allow the use of ifunc"),
-                                  cl::Hidden, cl::init(false));
-
 namespace {
 
 /// An instrumentation pass implementing detection of addressability bugs
 /// using tagged pointers.
 class HWAddressSanitizer : public FunctionPass {
 public:
   // Pass identification, replacement for typeid.
   static char ID;
if (auto Comdat =
     GV->setComdat(Comdat);
 }
 
 Value *HWAddressSanitizer::emitPrologue(IRBuilder<> &IRB,
                                         bool WithFrameRecord) {
   if (!Mapping.InTls)
     return getDynamicShadowNonTls(IRB);
 
-  if (ClAllowIfunc && !WithFrameRecord && TargetTriple.isAndroid())
+  if (!WithFrameRecord && TargetTriple.isAndroid())
     return getDynamicShadowIfunc(IRB);
 
   Value *SlotPtr = getHwasanThreadSlotPtr(IRB, IntptrTy);
   assert(SlotPtr);
 
   Instruction *ThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
 
   Function *F = IRB.GetInsertBlock()->getParent();

llvm/test/Instrumentation/HWAddressSanitizer/lazy-thread-init.ll

-; RUN: opt -S -hwasan -hwasan-allow-ifunc < %s | FileCheck %s
+; RUN: opt -S -hwasan < %s | FileCheck %s
 
 target triple = "aarch64--linux-android"
 
 declare i32 @bar([16 x i32]* %p)
 
 define void @alloca() sanitize_hwaddress "hwasan-abi"="interceptor" {
   ; CHECK: alloca [16 x i32]
   ; CHECK: [[A:%[^ ]*]] = call i8* @llvm.thread.pointer()

llvm/test/Instrumentation/HWAddressSanitizer/prologue.ll

 ; Test -hwasan-with-ifunc flag.
 ;
-; RUN: opt -hwasan -hwasan-allow-ifunc -S < %s | \
+; RUN: opt -hwasan -S < %s | \
 ; RUN:     FileCheck %s --check-prefixes=CHECK,CHECK-NOGLOBAL,CHECK-TLS,CHECK-HISTORY
-; RUN: opt -hwasan -hwasan-allow-ifunc -S -hwasan-with-ifunc=0 -hwasan-with-tls=1 -hwasan-record-stack-history=1 < %s | \
+; RUN: opt -hwasan -S -hwasan-with-ifunc=0 -hwasan-with-tls=1 -hwasan-record-stack-history=1 < %s | \
 ; RUN:     FileCheck %s --check-prefixes=CHECK,CHECK-NOGLOBAL,CHECK-TLS,CHECK-HISTORY
-; RUN: opt -hwasan -hwasan-allow-ifunc -S -hwasan-with-ifunc=0 -hwasan-with-tls=1 -hwasan-record-stack-history=0 < %s | \
+; RUN: opt -hwasan -S -hwasan-with-ifunc=0 -hwasan-with-tls=1 -hwasan-record-stack-history=0 < %s | \
 ; RUN:     FileCheck %s --check-prefixes=CHECK,CHECK-NOGLOBAL,CHECK-IFUNC,CHECK-NOHISTORY
-; RUN: opt -hwasan -hwasan-allow-ifunc -S -hwasan-with-ifunc=0 -hwasan-with-tls=0 < %s | \
+; RUN: opt -hwasan -S -hwasan-with-ifunc=0 -hwasan-with-tls=0 < %s | \
 ; RUN:     FileCheck %s --check-prefixes=CHECK,CHECK-GLOBAL,CHECK-NOHISTORY
-; RUN: opt -hwasan -hwasan-allow-ifunc -S -hwasan-with-ifunc=1  -hwasan-with-tls=0 < %s | \
+; RUN: opt -hwasan -S -hwasan-with-ifunc=1  -hwasan-with-tls=0 < %s | \
 ; RUN:     FileCheck %s --check-prefixes=CHECK,CHECk-NOGLOBAL,CHECK-IFUNC,CHECK-NOHISTORY
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64--linux-android22"
 
 ; CHECK-IFUNC: @__hwasan_shadow = external global [0 x i8]
 ; CHECK-NOIFUNC: @__hwasan_shadow_memory_dynamic_address = external global i64