[PATCH] D68236: Handle llvm.launder.invariant.group in msan.

[Ilya Tokar via Phabricator via llvm-commits]

TokarIP created this revision.
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TokarIP edited the summary of this revision.

[MSan] handle llvm.launder.invariant.group

  
  Msan used to give false-positives in
  
  class Foo {
   public:
    virtual ~Foo() {};
  };
  
  // Return true iff *x is set.
  bool f1(void **x, bool flag);
  
  Foo* f() {
    void *p;
    bool found;
    found = f1(&p,flag);
    if (found) {
      // p is always set here.
      return static_cast<Foo*>(p); // False positive here.
    }
    return nullptr;
  }


https://reviews.llvm.org/D68236

Files:
  llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
  llvm/test/Instrumentation/MemorySanitizer/msan_llvm_launder_invariant.ll


Index: llvm/test/Instrumentation/MemorySanitizer/msan_llvm_launder_invariant.ll
===================================================================
--- /dev/null
+++ llvm/test/Instrumentation/MemorySanitizer/msan_llvm_launder_invariant.ll
@@ -0,0 +1,38 @@
+; Make sure MSan handles llvm.launder.invariant.group correctly.
+
+; RUN: opt < %s -msan -msan-kernel=1 -O1 -S | FileCheck -check-prefixes=CHECK %s
+; RUN: opt < %s -msan -O1 -S | FileCheck -check-prefixes=CHECK %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%class.Foo = type { i32 (...)** }
+ at flag = dso_local local_unnamed_addr global i8 0, align 1
+
+define dso_local %class.Foo* @_Z1fv() local_unnamed_addr #0 {
+entry:
+  %p = alloca i8*, align 8
+  %0 = bitcast i8** %p to i8*
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* nonnull %0)
+  %1 = load i8, i8* @flag, align 1
+  %tobool = icmp ne i8 %1, 0
+  %call = call zeroext i1 @_Z2f1PPvb(i8** nonnull %p, i1 zeroext %tobool)
+  %2 = load i8*, i8** %p, align 8
+  %3 = call i8* @llvm.launder.invariant.group.p0i8(i8* %2)
+  %4 = bitcast i8* %3 to %class.Foo*
+  %retval.0 = select i1 %call, %class.Foo* %4, %class.Foo* null
+  call void @llvm.lifetime.end.p0i8(i64 8, i8* nonnull %0)
+  ret %class.Foo* %retval.0
+}
+
+; CHECK-NOT: call void @__msan_warning_noreturn
+
+declare dso_local zeroext i1 @_Z2f1PPvb(i8**, i1 zeroext) local_unnamed_addr
+
+declare i8* @llvm.launder.invariant.group.p0i8(i8*)
+
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
+
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
+
+attributes #0 = { sanitize_memory uwtable }
Index: llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -2562,6 +2562,12 @@
     return false;
   }
 
+  void handleLaunderInvariantGroup(IntrinsicInst &I) {
+    IRBuilder<> IRB(&I);
+    setShadow(&I, IRB.CreateBitCast(getShadow(&I, 0), getShadowTy(&I)));
+    setOrigin(&I, getOrigin(&I, 0));
+  }
+
   void handleLifetimeStart(IntrinsicInst &I) {
     if (!PoisonStack)
       return;
@@ -2993,6 +2999,9 @@
     case Intrinsic::lifetime_start:
       handleLifetimeStart(I);
       break;
+    case Intrinsic::launder_invariant_group:
+      handleLaunderInvariantGroup(I);
+      break;
     case Intrinsic::bswap:
       handleBswap(I);
       break;


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