[llvm] r226569 - [msan] Optimize -msan-check-constant-shadow.

[Evgeniy Stepanov]

Author: eugenis
Date: Tue Jan 20 09:21:35 2015
New Revision: 226569

URL: http://llvm.org/viewvc/llvm-project?rev=226569&view=rev
Log:
[msan] Optimize -msan-check-constant-shadow.

The new code does not create new basic blocks in the case when shadow is a
compile-time constant; it generates either an unconditional __msan_warning
call or nothing instead.

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
    llvm/trunk/test/Instrumentation/MemorySanitizer/check-constant-shadow.ll

Modified: llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp?rev=226569&r1=226568&r2=226569&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp Tue Jan 20 09:21:35 2015
@@ -611,11 +611,15 @@ struct MemorySanitizerVisitor : public I
                              OriginAlignment);
     } else {
       Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
-      // TODO(eugenis): handle non-zero constant shadow by inserting an
-      // unconditional check (can not simply fail compilation as this could
-      // be in the dead code).
-      if (!ClCheckConstantShadow)
-        if (isa<Constant>(ConvertedShadow)) return;
+      Constant *ConstantShadow = dyn_cast_or_null<Constant>(ConvertedShadow);
+      if (ConstantShadow) {
+        if (ClCheckConstantShadow && !ConstantShadow->isZeroValue())
+          IRB.CreateAlignedStore(updateOrigin(Origin, IRB),
+                                 getOriginPtr(Addr, IRB, Alignment),
+                                 OriginAlignment);
+        return;
+      }
+
       unsigned TypeSizeInBits =
           MS.DL->getTypeSizeInBits(ConvertedShadow->getType());
       unsigned SizeIndex = TypeSizeToSizeIndex(TypeSizeInBits);
@@ -670,9 +674,23 @@ struct MemorySanitizerVisitor : public I
     DEBUG(dbgs() << "  SHAD0 : " << *Shadow << "\n");
     Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
     DEBUG(dbgs() << "  SHAD1 : " << *ConvertedShadow << "\n");
-    // See the comment in storeOrigin().
-    if (!ClCheckConstantShadow)
-      if (isa<Constant>(ConvertedShadow)) return;
+
+    Constant *ConstantShadow = dyn_cast_or_null<Constant>(ConvertedShadow);
+    if (ConstantShadow) {
+      if (ClCheckConstantShadow && !ConstantShadow->isZeroValue()) {
+        if (MS.TrackOrigins) {
+          IRB.CreateStore(Origin ? (Value *)Origin : (Value *)IRB.getInt32(0),
+                          MS.OriginTLS);
+        }
+        IRB.CreateCall(MS.WarningFn);
+        IRB.CreateCall(MS.EmptyAsm);
+        // FIXME: Insert UnreachableInst if !ClKeepGoing?
+        // This may invalidate some of the following checks and needs to be done
+        // at the very end.
+      }
+      return;
+    }
+
     unsigned TypeSizeInBits =
         MS.DL->getTypeSizeInBits(ConvertedShadow->getType());
     unsigned SizeIndex = TypeSizeToSizeIndex(TypeSizeInBits);

Modified: llvm/trunk/test/Instrumentation/MemorySanitizer/check-constant-shadow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/MemorySanitizer/check-constant-shadow.ll?rev=226569&r1=226568&r2=226569&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/MemorySanitizer/check-constant-shadow.ll (original)
+++ llvm/trunk/test/Instrumentation/MemorySanitizer/check-constant-shadow.ll Tue Jan 20 09:21:35 2015
@@ -1,10 +1,11 @@
-; RUN: opt < %s -msan -msan-check-constant-shadow=1 -S | FileCheck %s
+; RUN: opt < %s -msan -msan-check-access-address=0 -msan-check-constant-shadow=1 -msan-track-origins=1 -S | 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"
 
 ; Test that returning a literal undef from main() triggers an MSan warning.
 
+; main() is special: it inserts check for the return value
 define i32 @main() nounwind uwtable sanitize_memory {
 entry:
   ret i32 undef
@@ -13,3 +14,40 @@ entry:
 ; CHECK-LABEL: @main
 ; CHECK: call void @__msan_warning_noreturn
 ; CHECK: ret i32 undef
+
+
+; This function stores known initialized value.
+; Expect 2 stores: one for the shadow (0), one for the value (42), but no origin.
+define void @StoreConstant(i32* nocapture %p) nounwind uwtable sanitize_memory {
+entry:
+  store i32 42, i32* %p, align 4
+  ret void
+}
+
+; CHECK-LABEL: @StoreConstant
+; CHECK-NOT: store i32
+; CHECK: store i32 0,
+; CHECK-NOT: store i32
+; CHECK: store i32 42,
+; CHECK-NOT: store i32
+; CHECK: ret void
+
+
+; This function stores known uninitialized value.
+; Expect 3 stores: shadow, value and origin.
+; Expect no icmp(s): everything here is unconditional.
+define void @StoreUndef(i32* nocapture %p) nounwind uwtable sanitize_memory {
+entry:
+  store i32 undef, i32* %p, align 4
+  ret void
+}
+
+; CHECK-LABEL: @StoreUndef
+; CHECK-NOT: icmp
+; CHECK: store i32
+; CHECK-NOT: icmp
+; CHECK: store i32
+; CHECK-NOT: icmp
+; CHECK: store i32
+; CHECK-NOT: icmp
+; CHECK: ret void