[msan] Avoid extra origin address realignment.

Do not realign origin address if the corresponding application
address is at least 4-byte-aligned.

Saves 2.5% code size in track-origins mode.

llvm-svn: 223464

1 files changed, 24 insertions, 21 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index 35f9fd7cce3..a11ad0f5913 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -522,9 +522,11 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
 
   void storeOrigin(IRBuilder<> &IRB, Value *Addr, Value *Shadow, Value *Origin,
                    unsigned Alignment, bool AsCall) {
+    unsigned OriginAlignment = std::max(kMinOriginAlignment, Alignment);
     if (isa<StructType>(Shadow->getType())) {
-      IRB.CreateAlignedStore(updateOrigin(Origin, IRB), getOriginPtr(Addr, IRB),
-                             Alignment);
+      IRB.CreateAlignedStore(updateOrigin(Origin, IRB),
+                             getOriginPtr(Addr, IRB, Alignment),
+                             OriginAlignment);
     } else {
       Value *ConvertedShadow = convertToShadowTyNoVec(Shadow, IRB);
       // TODO(eugenis): handle non-zero constant shadow by inserting an
@@ -549,7 +551,8 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
             Cmp, IRB.GetInsertPoint(), false, MS.OriginStoreWeights);
         IRBuilder<> IRBNew(CheckTerm);
         IRBNew.CreateAlignedStore(updateOrigin(Origin, IRBNew),
-                                  getOriginPtr(Addr, IRBNew), Alignment);
+                                  getOriginPtr(Addr, IRBNew, Alignment),
+                                  OriginAlignment);
       }
     }
   }
@@ -573,11 +576,9 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
 
       if (SI.isAtomic()) SI.setOrdering(addReleaseOrdering(SI.getOrdering()));
 
-      if (MS.TrackOrigins) {
-        unsigned Alignment = std::max(kMinOriginAlignment, SI.getAlignment());
-        storeOrigin(IRB, Addr, Shadow, getOrigin(Val), Alignment,
+      if (MS.TrackOrigins)
+        storeOrigin(IRB, Addr, Shadow, getOrigin(Val), SI.getAlignment(),
                     InstrumentWithCalls);
-      }
     }
   }
 
@@ -739,16 +740,17 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
   /// address.
   ///
   /// OriginAddr = (ShadowAddr + OriginOffset) & ~3ULL
-  Value *getOriginPtr(Value *Addr, IRBuilder<> &IRB) {
+  Value *getOriginPtr(Value *Addr, IRBuilder<> &IRB, unsigned Alignment) {
     Value *ShadowLong =
-      IRB.CreateAnd(IRB.CreatePointerCast(Addr, MS.IntptrTy),
-                    ConstantInt::get(MS.IntptrTy, ~MS.ShadowMask));
-    Value *Add =
-      IRB.CreateAdd(ShadowLong,
-                    ConstantInt::get(MS.IntptrTy, MS.OriginOffset));
-    Value *SecondAnd =
-      IRB.CreateAnd(Add, ConstantInt::get(MS.IntptrTy, ~3ULL));
-    return IRB.CreateIntToPtr(SecondAnd, PointerType::get(IRB.getInt32Ty(), 0));
+        IRB.CreateAnd(IRB.CreatePointerCast(Addr, MS.IntptrTy),
+                      ConstantInt::get(MS.IntptrTy, ~MS.ShadowMask));
+    Value *Origin = IRB.CreateAdd(
+        ShadowLong, ConstantInt::get(MS.IntptrTy, MS.OriginOffset));
+    if (Alignment < kMinOriginAlignment) {
+      uint64_t Mask = kMinOriginAlignment - 1;
+      Origin = IRB.CreateAnd(Origin, ConstantInt::get(MS.IntptrTy, ~Mask));
+    }
+    return IRB.CreateIntToPtr(Origin, PointerType::get(IRB.getInt32Ty(), 0));
   }
 
   /// \brief Compute the shadow address for a given function argument.
@@ -1052,9 +1054,10 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
 
     if (MS.TrackOrigins) {
       if (PropagateShadow) {
-        unsigned Alignment = std::max(kMinOriginAlignment, I.getAlignment());
-        setOrigin(&I,
-                  IRB.CreateAlignedLoad(getOriginPtr(Addr, IRB), Alignment));
+        unsigned Alignment = I.getAlignment();
+        unsigned OriginAlignment = std::max(kMinOriginAlignment, Alignment);
+        setOrigin(&I, IRB.CreateAlignedLoad(getOriginPtr(Addr, IRB, Alignment),
+                                            OriginAlignment));
       } else {
         setOrigin(&I, getCleanOrigin());
       }
@@ -1706,7 +1709,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     // FIXME: use ClStoreCleanOrigin
     // FIXME: factor out common code from materializeStores
     if (MS.TrackOrigins)
-      IRB.CreateStore(getOrigin(&I, 1), getOriginPtr(Addr, IRB));
+      IRB.CreateStore(getOrigin(&I, 1), getOriginPtr(Addr, IRB, 1));
     return true;
   }
 
@@ -1733,7 +1736,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
 
     if (MS.TrackOrigins) {
       if (PropagateShadow)
-        setOrigin(&I, IRB.CreateLoad(getOriginPtr(Addr, IRB)));
+        setOrigin(&I, IRB.CreateLoad(getOriginPtr(Addr, IRB, 1)));
       else
         setOrigin(&I, getCleanOrigin());
     }