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[CIR] Implement support for OffsetOfExpr #167726

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Merged
merged 1 commit into from
Nov 15, 2025
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[CIR] Implement support for OffsetOfExpr #167726

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17 changes: 17 additions & 0 deletions clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,8 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
return emitNullValue(e->getType(), cgf.getLoc(e->getSourceRange()));
}

mlir::Value VisitOffsetOfExpr(OffsetOfExpr *e);

mlir::Value VisitOpaqueValueExpr(OpaqueValueExpr *e) {
if (e->isGLValue())
return emitLoadOfLValue(cgf.getOrCreateOpaqueLValueMapping(e),
Expand Down Expand Up @@ -2207,6 +2209,21 @@ mlir::Value ScalarExprEmitter::VisitUnaryLNot(const UnaryOperator *e) {
return maybePromoteBoolResult(boolVal, cgf.convertType(e->getType()));
}

mlir::Value ScalarExprEmitter::VisitOffsetOfExpr(OffsetOfExpr *e) {
// Try folding the offsetof to a constant.
Expr::EvalResult evalResult;
if (e->EvaluateAsInt(evalResult, cgf.getContext())) {
mlir::Type type = cgf.convertType(e->getType());
llvm::APSInt value = evalResult.Val.getInt();
return builder.getConstAPInt(cgf.getLoc(e->getExprLoc()), type, value);
}

cgf.getCIRGenModule().errorNYI(
e->getSourceRange(),
"ScalarExprEmitter::VisitOffsetOfExpr Can't eval expr as int");
return {};
}

mlir::Value ScalarExprEmitter::VisitUnaryReal(const UnaryOperator *e) {
QualType promotionTy = getPromotionType(e->getSubExpr()->getType());
mlir::Value result = VisitRealImag(e, promotionTy);
Expand Down
93 changes: 93 additions & 0 deletions clang/test/CIR/CodeGen/offset-of.cpp
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@@ -0,0 +1,93 @@
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-cir %s -o %t.cir
// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-llvm %s -o %t-cir.ll
// RUN: FileCheck --input-file=%t-cir.ll %s -check-prefix=LLVM
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -Wno-unused-value -emit-llvm %s -o %t.ll
// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG

struct Struct {
int a;
float b;
double c;
bool d;
};

void offset_of_builtin() {
unsigned long a = __builtin_offsetof(Struct, a);
unsigned long b = __builtin_offsetof(Struct, b);
unsigned long c = __builtin_offsetof(Struct, c);
unsigned long d = __builtin_offsetof(Struct, d);
}

// CIR: %[[A_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["a", init]
// CIR: %[[B_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["b", init]
// CIR: %[[C_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["c", init]
// CIR: %[[D_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["d", init]
// CIR: %[[CONST_0:.*]] = cir.const #cir.int<0> : !u64i
// CIR: cir.store {{.*}} %[[CONST_0]], %[[A_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[CONST_4:.*]] = cir.const #cir.int<4> : !u64i
// CIR: cir.store {{.*}} %[[CONST_4]], %[[B_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[CONST_8:.*]] = cir.const #cir.int<8> : !u64i
// CIR: cir.store {{.*}} %[[CONST_8]], %[[C_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[CONST_16:.*]] = cir.const #cir.int<16> : !u64i
// CIR: cir.store {{.*}} %[[CONST_16]], %[[D_ADDR]] : !u64i, !cir.ptr<!u64i>

// LLVM: %[[A_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[B_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[C_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[D_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: store i64 0, ptr %[[A_ADDR]], align 8
// LLVM: store i64 4, ptr %[[B_ADDR]], align 8
// LLVM: store i64 8, ptr %[[C_ADDR]], align 8
// LLVM: store i64 16, ptr %[[D_ADDR]], align 8

// OGCG: %[[A_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[B_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[C_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[D_ADDR:.*]] = alloca i64, align 8
// OGCG: store i64 0, ptr %[[A_ADDR]], align 8
// OGCG: store i64 4, ptr %[[B_ADDR]], align 8
// OGCG: store i64 8, ptr %[[C_ADDR]], align 8
// OGCG: store i64 16, ptr %[[D_ADDR]], align 8

struct StructWithArray {
Struct array[4][4];
};

void offset_of_builtin_from_array_element() {
unsigned long a = __builtin_offsetof(StructWithArray, array[0][0].a);
unsigned long b = __builtin_offsetof(StructWithArray, array[1][1].b);
unsigned long c = __builtin_offsetof(StructWithArray, array[2][2].c);
unsigned long d = __builtin_offsetof(StructWithArray, array[3][3].d);
}

// CIR: %[[A_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["a", init]
// CIR: %[[B_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["b", init]
// CIR: %[[C_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["c", init]
// CIR: %[[D_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["d", init]
// CIR: %[[CONST_0:.*]] = cir.const #cir.int<0> : !u64i
// CIR: cir.store {{.*}} %[[CONST_0]], %[[A_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[CONST_124:.*]] = cir.const #cir.int<124> : !u64i
// CIR: cir.store {{.*}} %[[CONST_124]], %[[B_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[CONST_248:.*]] = cir.const #cir.int<248> : !u64i
// CIR: cir.store {{.*}} %[[CONST_248]], %[[C_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[CONST_376:.*]] = cir.const #cir.int<376> : !u64i
// CIR: cir.store {{.*}} %[[CONST_376]], %[[D_ADDR]] : !u64i, !cir.ptr<!u64i>

// LLVM: %[[A_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[B_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[C_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[D_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: store i64 0, ptr %[[A_ADDR]], align 8
// LLVM: store i64 124, ptr %[[B_ADDR]], align 8
// LLVM: store i64 248, ptr %[[C_ADDR]], align 8
// LLVM: store i64 376, ptr %[[D_ADDR]], align 8

// OGCG: %[[A_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[B_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[C_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[D_ADDR:.*]] = alloca i64, align 8
// OGCG: store i64 0, ptr %[[A_ADDR]], align 8
// OGCG: store i64 124, ptr %[[B_ADDR]], align 8
// OGCG: store i64 248, ptr %[[C_ADDR]], align 8
// OGCG: store i64 376, ptr %[[D_ADDR]], align 8
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