[clang] [TBAA] Emit distinct TBAA tags for pointers with different depths,types. (PR #76612)
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Sat Dec 30 02:56:21 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Florian Hahn (fhahn)
<details>
<summary>Changes</summary>
This patch extends Clang's TBAA generation code to emit distinct tags for incompatible pointer types.
Pointers with different element types are incompatible if the pointee types are also incompatible (modulo sugar/modifiers).
Express this in TBAA by generating different tags for pointers based on the pointer depth and pointee type. To get the TBAA tag for the pointee type it uses getTypeInfoHelper on the pointee type.
(Moved from https://reviews.llvm.org/D122573)
---
Full diff: https://github.com/llvm/llvm-project/pull/76612.diff
2 Files Affected:
- (modified) clang/lib/CodeGen/CodeGenTBAA.cpp (+25-4)
- (modified) clang/test/CodeGen/tbaa-pointers.c (+42-30)
``````````diff
diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp
index dc288bc3f6157a..b96f9d28c45530 100644
--- a/clang/lib/CodeGen/CodeGenTBAA.cpp
+++ b/clang/lib/CodeGen/CodeGenTBAA.cpp
@@ -184,10 +184,31 @@ llvm::MDNode *CodeGenTBAA::getTypeInfoHelper(const Type *Ty) {
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);
+ if (Ty->isPointerType() || Ty->isReferenceType()) {
+ llvm::MDNode *AnyPtr = createScalarTypeNode("any pointer", getChar(), Size);
+ // Compute the depth of the pointer and generate a tag of the form "p<depth>
+ // <base type tag>".
+ unsigned PtrDepth = 0;
+ do {
+ PtrDepth++;
+ Ty = Ty->getPointeeType().getTypePtr();
+ } while (Ty->isPointerType() || Ty->isReferenceType());
+ // TODO: Implement C++'s type "similarity" and consider dis-"similar"
+ // pointers distinct for non-builtin types.
+ if (isa<BuiltinType>(Ty)) {
+ llvm::MDNode *ScalarMD = getTypeInfoHelper(Ty);
+ StringRef Name =
+ cast<llvm::MDString>(
+ ScalarMD->getOperand(CodeGenOpts.NewStructPathTBAA ? 2 : 0))
+ ->getString();
+ SmallString<256> OutName("p");
+ OutName += std::to_string(PtrDepth);
+ OutName += " ";
+ OutName += Name;
+ return createScalarTypeNode(OutName, AnyPtr, Size);
+ }
+ return AnyPtr;
+ }
// Accesses to arrays are accesses to objects of their element types.
if (CodeGenOpts.NewStructPathTBAA && Ty->isArrayType())
diff --git a/clang/test/CodeGen/tbaa-pointers.c b/clang/test/CodeGen/tbaa-pointers.c
index b9ebe879820012..a3a7aa0d66473e 100644
--- a/clang/test/CodeGen/tbaa-pointers.c
+++ b/clang/test/CodeGen/tbaa-pointers.c
@@ -4,9 +4,9 @@ void p2unsigned(unsigned **ptr) {
// CHECK-LABEL: define void @p2unsigned(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0:!.+]]
- // CHECK-NEXT: [[BASE:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store ptr null, ptr [[BASE]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P2INT_0:!.+]]
+ // CHECK-NEXT: [[BASE:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P2INT_0]]
+ // CHECK-NEXT: store ptr null, ptr [[BASE]], align 8, !tbaa [[P1INT_0:!.+]]
// CHECK-NEXT: ret void
//
*ptr = 0;
@@ -16,9 +16,9 @@ void p2unsigned_volatile(unsigned *volatile *ptr) {
// CHECK-LABEL: define void @p2unsigned_volatile(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store volatile ptr null, ptr [[BASE]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P2INT_0]]
+ // CHECK-NEXT: [[BASE:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P2INT_0]]
+ // CHECK-NEXT: store volatile ptr null, ptr [[BASE]], align 8, !tbaa [[P1INT_0]]
// CHECK-NEXT: ret void
//
*ptr = 0;
@@ -28,10 +28,10 @@ void p3int(int ***ptr) {
// CHECK-LABEL: define void @p3int(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store ptr null, ptr [[BASE_1]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P3INT_0:!.+]]
+ // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P3INT_0]]
+ // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[P2INT_0]]
+ // CHECK-NEXT: store ptr null, ptr [[BASE_1]], align 8, !tbaa [[P1INT_0]]
// CHECK-NEXT: ret void
//
**ptr = 0;
@@ -41,11 +41,11 @@ void p4char(char ****ptr) {
// CHECK-LABEL: define void @p4char(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_2:%.+]] = load ptr, ptr [[BASE_1]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store ptr null, ptr [[BASE_2]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P4CHAR_0:!.+]]
+ // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P4CHAR_0]]
+ // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[P3CHAR_0:!.+]]
+ // CHECK-NEXT: [[BASE_2:%.+]] = load ptr, ptr [[BASE_1]], align 8, !tbaa [[P2CHAR_0:!.+]]
+ // CHECK-NEXT: store ptr null, ptr [[BASE_2]], align 8, !tbaa [[P1CHAR_0:!.+]]
// CHECK-NEXT: ret void
//
***ptr = 0;
@@ -55,11 +55,11 @@ void p4char_const1(const char ****ptr) {
// CHECK-LABEL: define void @p4char_const1(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_2:%.+]] = load ptr, ptr [[BASE_1]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store ptr null, ptr [[BASE_2]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P4CHAR_0]]
+ // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P4CHAR_0]]
+ // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[P3CHAR_0]]
+ // CHECK-NEXT: [[BASE_2:%.+]] = load ptr, ptr [[BASE_1]], align 8, !tbaa [[P2CHAR_0]]
+ // CHECK-NEXT: store ptr null, ptr [[BASE_2]], align 8, !tbaa [[P1CHAR_0]]
// CHECK-NEXT: ret void
//
***ptr = 0;
@@ -69,11 +69,11 @@ void p4char_const2(const char **const **ptr) {
// CHECK-LABEL: define void @p4char_const2(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE_2:%.+]] = load ptr, ptr [[BASE_1]], align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store ptr null, ptr [[BASE_2]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P4CHAR_0]]
+ // CHECK-NEXT: [[BASE_0:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P4CHAR_0]]
+ // CHECK-NEXT: [[BASE_1:%.+]] = load ptr, ptr [[BASE_0]], align 8, !tbaa [[P3CHAR_0]]
+ // CHECK-NEXT: [[BASE_2:%.+]] = load ptr, ptr [[BASE_1]], align 8, !tbaa [[P2CHAR_0]]
+ // CHECK-NEXT: store ptr null, ptr [[BASE_2]], align 8, !tbaa [[P1CHAR_0]]
// CHECK-NEXT: ret void
//
***ptr = 0;
@@ -88,16 +88,28 @@ void p2struct(struct S1 **ptr) {
// CHECK-LABEL: define void @p2struct(ptr noundef %ptr)
// CHECK-NEXT: entry:
// CHECK-NEXT: %ptr.addr = alloca ptr, align 8
- // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: [[BASE:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[ANY_POINTER_0]]
- // CHECK-NEXT: store ptr null, ptr [[BASE]], align 8, !tbaa [[ANY_POINTER_0]]
+ // CHECK-NEXT: store ptr %ptr, ptr %ptr.addr, align 8, !tbaa [[P2S1_0:!.+]]
+ // CHECK-NEXT: [[BASE:%.+]] = load ptr, ptr %ptr.addr, align 8, !tbaa [[P2S1_0]]
+ // CHECK-NEXT: store ptr null, ptr [[BASE]], align 8, !tbaa [[P1S1_:!.+]]
// CHECK-NEXT: ret void
//
*ptr = 0;
}
-// CHECK: [[ANY_POINTER_0]] = !{[[ANY_POINTER:!.+]], [[ANY_POINTER]], i64 0}
+// CHECK: [[P2INT_0]] = !{[[P2INT:!.+]], [[P2INT]], i64 0}
+// CHECK: [[P2INT]] = !{!"p2 int", [[ANY_POINTER:!.+]], i64 0}
// CHECK: [[ANY_POINTER]] = !{!"any pointer", [[CHAR:!.+]], i64 0}
// CHECK: [[CHAR]] = !{!"omnipotent char", [[TBAA_ROOT:!.+]], i64 0}
// CHECK: [[TBAA_ROOT]] = !{!"Simple C/C++ TBAA"}
-//
+// CHECK: [[P1INT_0]] = !{[[P1INT:!.+]], [[P1INT]], i64 0}
+// CHECK: [[P1INT]] = !{!"p1 int", [[ANY_POINTER]], i64 0}
+// CHECK: [[P3INT_0]] = !{[[P3INT:!.+]], [[P3INT]], i64 0}
+// CHECK: [[P3INT]] = !{!"p3 int", [[ANY_POINTER]], i64 0}
+// CHECK: [[P4CHAR_0]] = !{[[P4CHAR:!.+]], [[P4CHAR]], i64 0}
+// CHECK: [[P4CHAR]] = !{!"p4 omnipotent char", [[ANY_POINTER]], i64 0}
+// CHECK: [[P3CHAR_0]] = !{[[P3CHAR:!.+]], [[P3CHAR]], i64 0}
+// CHECK: [[P3CHAR]] = !{!"p3 omnipotent char", [[ANY_POINTER]], i64 0}
+// CHECK: [[P2CHAR_0]] = !{[[P2CHAR:!.+]], [[P2CHAR]], i64 0}
+// CHECK: [[P2CHAR]] = !{!"p2 omnipotent char", [[ANY_POINTER]], i64 0}
+// CHECK: [[P1CHAR_0]] = !{[[P1CHAR:!.+]], [[P1CHAR]], i64 0}
+// CHECK: [[P1CHAR]] = !{!"p1 omnipotent char", [[ANY_POINTER]], i64 0}
``````````
</details>
https://github.com/llvm/llvm-project/pull/76612
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