[msan] Remove more attributes from sanitized functions.

[eugenis]

Summary

MSan instrumentation adds stores and loads even to pure
readonly/writeonly functions. It is removing some of those attributes
from instrumented functions and call targets, but apparently not enough.

Remove writeonly, argmemonly and speculatable in addition to readonly /
readnone.

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

if (CS.isCall()) {
       // We are going to insert code that relies on the fact that the callee
       // will become a non-readonly function after it is instrumented by us. To
       // prevent this code from being optimized out, mark that function
       // non-readonly in advance.
       if (Function *Func = Call->getCalledFunction()) {
         // Clear out readonly/readnone attributes.
         AttrBuilder B;
         B.addAttribute(Attribute::ReadOnly)
-          .addAttribute(Attribute::ReadNone);
+            .addAttribute(Attribute::ReadNone)
+            .addAttribute(Attribute::WriteOnly)
+            .addAttribute(Attribute::ArgMemOnly)
+            .addAttribute(Attribute::Speculatable);
         Func->removeAttributes(AttributeList::FunctionIndex, B);
       }
 
       maybeMarkSanitizerLibraryCallNoBuiltin(Call, TLI);
     }
     IRBuilder<> IRB(&I);
 
     unsigned ArgOffset = 0;
bool MemorySanitizer::sanitizeFunction(Function &F, TargetLibraryInfo &TLI) {
   if (!CompileKernel && F.getName() == kMsanModuleCtorName)
     return false;
 
   MemorySanitizerVisitor Visitor(F, *this, TLI);
 
   // Clear out readonly/readnone attributes.
   AttrBuilder B;
   B.addAttribute(Attribute::ReadOnly)
-    .addAttribute(Attribute::ReadNone);
+      .addAttribute(Attribute::ReadNone)
+      .addAttribute(Attribute::WriteOnly)
+      .addAttribute(Attribute::ArgMemOnly)
+      .addAttribute(Attribute::Speculatable);
   F.removeAttributes(AttributeList::FunctionIndex, B);
 
   return Visitor.runOnFunction();
 }

llvm/test/Instrumentation/MemorySanitizer/attributes.ll

+; RUN: opt < %s -S -passes='module(msan-module),function(msan)' 2>&1 | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+
+declare void @a_() sanitize_memory readnone
+declare void @b_() sanitize_memory readonly
+declare void @c_() sanitize_memory writeonly
+declare void @d_(i32* %p) sanitize_memory writeonly argmemonly
+declare void @e_() sanitize_memory speculatable
+
+define void @a() sanitize_memory readnone {
+entry:
+  call void @a_()
+  ret void
+}
+
+define void @b() sanitize_memory readonly {
+entry:
+  call void @b_()
+  ret void
+}
+
+define void @c() sanitize_memory writeonly {
+entry:
+  call void @c_()
+  ret void
+}
+
+define void @d(i32* %p) sanitize_memory writeonly argmemonly {
+entry:
+  call void @d_(i32* %p)
+  ret void
+}
+
+define void @e() sanitize_memory speculatable {
+entry:
+  call void @e_()
+  ret void
+}
+
+; CHECK-NOT: readnone
+; CHECK-NOT: readonly
+; CHECK-NOT: writeonly
+; CHECK-NOT: argmemonly
+; CHECK-NOT: speculatable