[PATCH] D11034: Respect alignment of nested bitfields

[Ulrich Weigand]

uweigand updated this revision to Diff 29347.
uweigand added a comment.

Addressed review comments:

- Use CreateAlignedLoad / CreateAlignedStore


http://reviews.llvm.org/D11034

Files:
  lib/CodeGen/CGExpr.cpp
  test/CodeGen/packed-nest-unpacked.c

Index: test/CodeGen/packed-nest-unpacked.c
===================================================================
--- test/CodeGen/packed-nest-unpacked.c
+++ test/CodeGen/packed-nest-unpacked.c
@@ -60,6 +60,35 @@
 
 unsigned test7() {
   // CHECK: @test7
-  // CHECK: load i32, i32* getelementptr inbounds (%struct.YBitfield, %struct.YBitfield* @gbitfield, i32 0, i32 1, i32 0), align 4
+  // CHECK: load i32, i32* getelementptr inbounds (%struct.YBitfield, %struct.YBitfield* @gbitfield, i32 0, i32 1, i32 0), align 1
   return gbitfield.y.b2;
 }
+
+void test8(unsigned x) {
+  // CHECK: @test8
+  // CHECK: load i32, i32* getelementptr inbounds (%struct.YBitfield, %struct.YBitfield* @gbitfield, i32 0, i32 1, i32 0), align 1
+  // CHECK: store i32 {{.*}}, i32* getelementptr inbounds (%struct.YBitfield, %struct.YBitfield* @gbitfield, i32 0, i32 1, i32 0), align 1
+  gbitfield.y.b2 = x;
+}
+
+struct TBitfield
+{
+  long a;
+  char b;
+  unsigned c:15;
+};
+struct TBitfield tbitfield;
+
+unsigned test9() {
+  // CHECK: @test9
+  // CHECK: load i16, i16* getelementptr inbounds (%struct.TBitfield, %struct.TBitfield* @tbitfield, i32 0, i32 2), align 1
+  return tbitfield.c;
+}
+
+void test10(unsigned x) {
+  // CHECK: @test10
+  // CHECK: load i16, i16* getelementptr inbounds (%struct.TBitfield, %struct.TBitfield* @tbitfield, i32 0, i32 2), align 1
+  // CHECK: store i16 {{.*}}, i16* getelementptr inbounds (%struct.TBitfield, %struct.TBitfield* @tbitfield, i32 0, i32 2), align 1
+  tbitfield.c = x;
+}
+
Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp
+++ lib/CodeGen/CGExpr.cpp
@@ -1356,14 +1356,16 @@
 
 RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV) {
   const CGBitFieldInfo &Info = LV.getBitFieldInfo();
+  int64_t Align = Info.StorageAlignment;
+  if (!LV.getAlignment().isZero())
+    Align = std::min(Align, LV.getAlignment().getQuantity());
 
   // Get the output type.
   llvm::Type *ResLTy = ConvertType(LV.getType());
 
   llvm::Value *Ptr = LV.getBitFieldAddr();
-  llvm::Value *Val = Builder.CreateLoad(Ptr, LV.isVolatileQualified(),
-                                        "bf.load");
-  cast<llvm::LoadInst>(Val)->setAlignment(Info.StorageAlignment);
+  llvm::Value *Val =
+    Builder.CreateAlignedLoad(Ptr, Align, LV.isVolatileQualified(), "bf.load");
 
   if (Info.IsSigned) {
     assert(static_cast<unsigned>(Info.Offset + Info.Size) <= Info.StorageSize);
@@ -1559,6 +1561,9 @@
 void CodeGenFunction::EmitStoreThroughBitfieldLValue(RValue Src, LValue Dst,
                                                      llvm::Value **Result) {
   const CGBitFieldInfo &Info = Dst.getBitFieldInfo();
+  int64_t Align = Info.StorageAlignment;
+  if (!Dst.getAlignment().isZero())
+    Align = std::min(Align, Dst.getAlignment().getQuantity());
   llvm::Type *ResLTy = ConvertTypeForMem(Dst.getType());
   llvm::Value *Ptr = Dst.getBitFieldAddr();
 
@@ -1575,9 +1580,9 @@
   // and mask together with source before storing.
   if (Info.StorageSize != Info.Size) {
     assert(Info.StorageSize > Info.Size && "Invalid bitfield size.");
-    llvm::Value *Val = Builder.CreateLoad(Ptr, Dst.isVolatileQualified(),
-                                          "bf.load");
-    cast<llvm::LoadInst>(Val)->setAlignment(Info.StorageAlignment);
+    llvm::Value *Val = Builder.CreateAlignedLoad(Ptr, Align,
+                                                 Dst.isVolatileQualified(),
+                                                 "bf.load");
 
     // Mask the source value as needed.
     if (!hasBooleanRepresentation(Dst.getType()))
@@ -1603,9 +1608,8 @@
   }
 
   // Write the new value back out.
-  llvm::StoreInst *Store = Builder.CreateStore(SrcVal, Ptr,
-                                               Dst.isVolatileQualified());
-  Store->setAlignment(Info.StorageAlignment);
+  llvm::StoreInst *Store =
+    Builder.CreateAlignedStore(SrcVal, Ptr, Align, Dst.isVolatileQualified());
 
   // Return the new value of the bit-field, if requested.
   if (Result) {


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