[CodeGen] Represent array members in new-format TBAA type descriptors

[kosarev]

Summary

Now that in the new TBAA format we allow access types to be of any object types, including aggregate ones, it becomes critical to specify types of all sub-objects such aggregates comprise as their members. In order to meet this requirement, this patch enables generation of field descriptors for members of array types.

This patch requires D41394 to be landed first.

[hfinkel]

test/CodeGen/tbaa-array.cpp

24 ↗

(On Diff #127537)

Shouldn't this access have a size of 4, and an access for c->x[2] have a size of 4 and a specific offset and c->x[j] have a size of 12 and an offset of zero? Why does this list a size of 16?

In any case, please add tests for:

int *bar2(C *c) {
  return c->x;
}

int bar3(C *c) {
  return c->x[2];
}

int bar4(C *c, int j) {
  return c->x[j];
}

[kosarev]

test/CodeGen/tbaa-array.cpp

24 ↗

(On Diff #127537)

Indeed, the access size is wrong as we mistakenly inherit it from the base type. D41452 fixes this. Thanks for catching.

[kosarev]

test/CodeGen/tbaa-array.cpp

24 ↗

(On Diff #127537)

Hal, in bar2() we don't really access memory. What do we want to check with it?

[hfinkel]

test/CodeGen/tbaa-array.cpp

24 ↗

(On Diff #127537)

Hal, in bar2() we don't really access memory. What do we want to check with it?

Ah, good point. Ignore that one.

[kosarev]

• Fixed the access size.
• Added the suggested tests.

[hfinkel]

LGTM. The array accesses here are just being represented as their scalar-access types. In the future, we should update this to represent them as fields in their parent structs, but this is fine for now.

cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp

if (Ty->isStdByteType())
     return getChar();
 
   // Handle pointers and references.
   // TODO: Implement C++'s type "similarity" and consider dis-"similar"
   // pointers distinct.
   if (Ty->isPointerType() || Ty->isReferenceType())
     return createScalarTypeNode("any pointer", getChar(), Size);
 
+  // Accesses to arrays are accesses to objects of their element types.
+  if (CodeGenOpts.NewStructPathTBAA && Ty->isArrayType())
+    return getTypeInfo(cast<ArrayType>(Ty)->getElementType());
+
   // Enum types are distinct types. In C++ they have "underlying types",
   // however they aren't related for TBAA.
   if (const EnumType *ETy = dyn_cast<EnumType>(Ty)) {
     // In C++ mode, types have linkage, so we can rely on the ODR and
     // on their mangled names, if they're external.
     // TODO: Is there a way to get a program-wide unique name for a
     // decl with local linkage or no linkage?
     if (!Features.CPlusPlus || !ETy->getDecl()->isExternallyVisible())

cfe/trunk/test/CodeGen/tbaa-array.cpp

 // RUN: %clang_cc1 -triple x86_64-linux -O1 -disable-llvm-passes %s \
 // RUN:     -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-linux -O1 -disable-llvm-passes %s \
+// RUN:     -new-struct-path-tbaa -emit-llvm -o - | \
+// RUN:     FileCheck -check-prefix=CHECK-NEW %s
 //
 // Check that we generate correct TBAA information for accesses to array
 // elements.
 
 struct A { int i; };
 struct B { A a[1]; };
+struct C { int i; int x[3]; };
 
 int foo(B *b) {
 // CHECK-LABEL: _Z3fooP1B
 // CHECK: load i32, {{.*}}, !tbaa [[TAG_A_i:!.*]]
+// CHECK-NEW-LABEL: _Z3fooP1B
+// CHECK-NEW: load i32, {{.*}}, !tbaa [[TAG_A_i:!.*]]
   return b->a->i;
 }
 
+// Check that members of array types are represented correctly.
+int bar(C *c) {
+// CHECK-NEW-LABEL: _Z3barP1C
+// CHECK-NEW: load i32, {{.*}}, !tbaa [[TAG_C_i:!.*]]
+  return c->i;
+}
+
+int bar2(C *c) {
+// CHECK-NEW-LABEL: _Z4bar2P1C
+// CHECK-NEW: load i32, {{.*}}, !tbaa [[TAG_int:!.*]]
+  return c->x[2];
+}
+
+int bar3(C *c, int j) {
+// CHECK-NEW-LABEL: _Z4bar3P1Ci
+// CHECK-NEW: load i32, {{.*}}, !tbaa [[TAG_int:!.*]]
+  return c->x[j];
+}
+
 // CHECK-DAG: [[TAG_A_i]] = !{[[TYPE_A:!.*]], [[TYPE_int:!.*]], i64 0}
 // CHECK-DAG: [[TYPE_A]] = !{!"_ZTS1A", !{{.*}}, i64 0}
 // CHECK-DAG: [[TYPE_int]] = !{!"int", !{{.*}}, i64 0}
+
+// CHECK-NEW-DAG: [[TYPE_char:!.*]] = !{{{.*}}, i64 1, !"omnipotent char"}
+// CHECK-NEW-DAG: [[TYPE_int:!.*]] = !{[[TYPE_char]], i64 4, !"int"}
+// CHECK-NEW-DAG: [[TAG_int]] = !{[[TYPE_int]], [[TYPE_int]], i64 0, i64 4}
+// CHECK-NEW-DAG: [[TYPE_pointer:!.*]] = !{[[TYPE_char]], i64 8, !"any pointer"}
+// CHECK-NEW-DAG: [[TYPE_A:!.*]] = !{[[TYPE_char]], i64 4, !"_ZTS1A", [[TYPE_int]], i64 0, i64 4}
+// CHECK-NEW-DAG: [[TAG_A_i]] = !{[[TYPE_A]], [[TYPE_int]], i64 0, i64 4}
+// CHECK-NEW-DAG: [[TYPE_C:!.*]] = !{[[TYPE_char]], i64 16, !"_ZTS1C", [[TYPE_int]], i64 0, i64 4, [[TYPE_int]], i64 4, i64 12}
+// CHECK-NEW-DAG: [[TAG_C_i]] = !{[[TYPE_C:!.*]], [[TYPE_int:!.*]], i64 0, i64 4}