CodeGen: specify alignment + inbounds for automatic variable initialization

Summary: Automatic variable initialization was generating default-aligned stores (which are deprecated) instead of using the known alignment from the alloca. Further, they didn't specify inbounds.

Subscribers: dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D49209

llvm-svn: 337041

2 files changed, 25 insertions, 7 deletions

diff --git a/clang/lib/CodeGen/CGBuilder.h b/clang/lib/CodeGen/CGBuilder.h
index 5b9c7a3c46a..d2e5eb256d3 100644
--- a/clang/lib/CodeGen/CGBuilder.h
+++ b/clang/lib/CodeGen/CGBuilder.h
@@ -244,6 +244,21 @@ public:
                    Addr.getAlignment().alignmentAtOffset(Offset));
   }
 
+  using CGBuilderBaseTy::CreateConstInBoundsGEP2_32;
+  Address CreateConstInBoundsGEP2_32(Address Addr, unsigned Idx0,
+                                      unsigned Idx1, const llvm::DataLayout &DL,
+                                      const llvm::Twine &Name = "") {
+    auto *GEP = cast<llvm::GetElementPtrInst>(CreateConstInBoundsGEP2_32(
+        Addr.getElementType(), Addr.getPointer(), Idx0, Idx1, Name));
+    llvm::APInt Offset(
+        DL.getIndexSizeInBits(Addr.getType()->getPointerAddressSpace()), 0,
+        /*IsSigned=*/true);
+    if (!GEP->accumulateConstantOffset(DL, Offset))
+      llvm_unreachable("offset of GEP with constants is always computable");
+    return Address(GEP, Addr.getAlignment().alignmentAtOffset(
+                            CharUnits::fromQuantity(Offset.getSExtValue())));
+  }
+
   llvm::Value *CreateConstInBoundsByteGEP(llvm::Value *Ptr, CharUnits Offset,
                                           const llvm::Twine &Name = "") {
     assert(Ptr->getType()->getPointerElementType() == TypeCache.Int8Ty);
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 1e9a7d5856d..9350e88f2eb 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -888,15 +888,17 @@ static bool canEmitInitWithFewStoresAfterMemset(llvm::Constant *Init,
 /// emitStoresForInitAfterMemset - For inits that
 /// canEmitInitWithFewStoresAfterMemset returned true for, emit the scalar
 /// stores that would be required.
-static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc,
-                                         bool isVolatile, CGBuilderTy &Builder) {
+static void emitStoresForInitAfterMemset(CodeGenModule &CGM,
+                                         llvm::Constant *Init, Address Loc,
+                                         bool isVolatile,
+                                         CGBuilderTy &Builder) {
   assert(!Init->isNullValue() && !isa<llvm::UndefValue>(Init) &&
          "called emitStoresForInitAfterMemset for zero or undef value.");
 
   if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) ||
       isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) ||
       isa<llvm::ConstantExpr>(Init)) {
-    Builder.CreateDefaultAlignedStore(Init, Loc, isVolatile);
+    Builder.CreateStore(Init, Loc, isVolatile);
     return;
   }
 
@@ -908,7 +910,8 @@ static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc,
       // If necessary, get a pointer to the element and emit it.
       if (!Elt->isNullValue() && !isa<llvm::UndefValue>(Elt))
         emitStoresForInitAfterMemset(
-            Elt, Builder.CreateConstGEP2_32(Init->getType(), Loc, 0, i),
+            CGM, Elt,
+            Builder.CreateConstInBoundsGEP2_32(Loc, 0, i, CGM.getDataLayout()),
             isVolatile, Builder);
     }
     return;
@@ -923,7 +926,8 @@ static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc,
     // If necessary, get a pointer to the element and emit it.
     if (!Elt->isNullValue() && !isa<llvm::UndefValue>(Elt))
       emitStoresForInitAfterMemset(
-          Elt, Builder.CreateConstGEP2_32(Init->getType(), Loc, 0, i),
+          CGM, Elt,
+          Builder.CreateConstInBoundsGEP2_32(Loc, 0, i, CGM.getDataLayout()),
           isVolatile, Builder);
   }
 }
@@ -1411,8 +1415,7 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) {
     if (!constant->isNullValue() && !isa<llvm::UndefValue>(constant)) {
       Loc = Builder.CreateBitCast(Loc,
         constant->getType()->getPointerTo(Loc.getAddressSpace()));
-      emitStoresForInitAfterMemset(constant, Loc.getPointer(),
-                                   isVolatile, Builder);
+      emitStoresForInitAfterMemset(CGM, constant, Loc, isVolatile, Builder);
     }
   } else {
     // Otherwise, create a temporary global with the initializer then