dec90ffbc9
Fix two bugs in CIR's handling of `[[no_unique_address]]` fields: - Record layout: Use the base subobject type (without tail padding) instead of the complete object type for [[no_unique_address]] fields, allowing subsequent fields to overlap with tail padding. - Field access: Insert bitcasts from the base subobject pointer to the complete object pointer after cir.get_member for potentially-overlapping fields, so downstream code sees the expected type. - Zero-sized fields: Handle truly empty [[no_unique_address]] fields by computing their address via byte offsets rather than cir.get_member, since they have no entry in the record layout. A known gap (CIR copies 8 bytes where OG copies 5 via `ConstructorMemcpyizer`) is noted for follow-up.
54 lines
2.3 KiB
C++
54 lines
2.3 KiB
C++
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu \
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// RUN: -fclangir -emit-cir %s -o %t.cir
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// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
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// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu \
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// RUN: -fclangir -emit-llvm %s -o %t.ll
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// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
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// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu \
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// RUN: -emit-llvm %s -o %t.og.ll
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// RUN: FileCheck --check-prefix=OGCG --input-file=%t.og.ll %s
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struct Base {
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int x;
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};
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struct Middle : Base {
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char c;
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// sizeof(Middle) = 8 (4 for x, 1 for c, 3 tail padding)
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// data size = 5
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};
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struct Outer {
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[[no_unique_address]] Middle m;
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char extra;
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Outer(const Middle &m, char e) : m(m), extra(e) {}
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};
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// The record layout should use the base subobject type for the
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// [[no_unique_address]] field, allowing 'extra' to overlap with
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// Middle's tail padding.
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// CIR: !rec_Middle2Ebase = !cir.record<struct "Middle.base" packed {!rec_Base, !s8i}>
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// CIR: !rec_Outer = !cir.record<struct "Outer" padded {!rec_Middle2Ebase, !s8i,
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// CIR-LABEL: cir.func {{.*}} @_ZN5OuterC2ERK6Middlec(
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// CIR: %[[THIS:.*]] = cir.load %{{.+}} : !cir.ptr<!cir.ptr<!rec_Outer>>, !cir.ptr<!rec_Outer>
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// CIR: %[[M_BASE:.*]] = cir.get_member %[[THIS]][0] {name = "m"} : !cir.ptr<!rec_Outer> -> !cir.ptr<!rec_Middle2Ebase>
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// CIR-NEXT: %[[M_COMPLETE:.*]] = cir.cast bitcast %[[M_BASE]] : !cir.ptr<!rec_Middle2Ebase> -> !cir.ptr<!rec_Middle>
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// CIR: cir.copy %{{.+}} to %[[M_COMPLETE]] : !cir.ptr<!rec_Middle>
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// CIR: %[[EXTRA:.*]] = cir.get_member %[[THIS]][1] {name = "extra"} : !cir.ptr<!rec_Outer> -> !cir.ptr<!s8i>
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// LLVM-LABEL: define {{.*}} void @_ZN5OuterC2ERK6Middlec(
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// LLVM: %[[GEP:.*]] = getelementptr %struct.Outer, ptr %{{.+}}, i32 0, i32 0
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// LLVM: call void @llvm.memcpy.p0.p0.i64(ptr %[[GEP]], ptr %{{.+}}, i64 8, i1 false)
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// OGCG-LABEL: define {{.*}} void @_ZN5OuterC2ERK6Middlec(
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// OGCG: %[[GEP:.*]] = getelementptr inbounds nuw %struct.Outer, ptr %{{.+}}, i32 0, i32 0
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// TODO(CIR): OG emits i64 5 here via ConstructorMemcpyizer, which CIR
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// doesn't have yet. CIR copies the full 8-byte type instead.
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// OGCG: call void @llvm.memcpy.p0.p0.i64(ptr {{.*}} %[[GEP]], ptr {{.*}} %{{.+}}, i64 5, i1 false)
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void test(const Middle &m) {
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Outer o(m, 'x');
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}
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