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4497ec293a
This is a follow-up from the conversation starting at https://github.com/llvm/llvm-project/pull/93809#issuecomment-2173729801 The root problem that motivated the change are external AST sources that compute `ASTRecordLayout`s themselves instead of letting Clang compute them from the AST. One such example is LLDB using DWARF to get the definitive offsets and sizes of C++ structures. Such layouts should be considered correct (modulo buggy DWARF), but various assertions and lowering logic around the `CGRecordLayoutBuilder` relies on the AST having `[[no_unique_address]]` attached to them. This is a layout-altering attribute which is not encoded in DWARF. This causes us LLDB to trip over the various LLVM<->Clang layout consistency checks. There has been precedent for avoiding such layout-altering attributes from affecting lowering with externally-provided layouts (e.g., packed structs). This patch proposes to replace the `isZeroSize` checks in `CGRecordLayoutBuilder` (which roughly means "empty field with [[no_unique_address]]") with checks for `CodeGen::isEmptyField`/`CodeGen::isEmptyRecord`. **Details** The main strategy here was to change the `isZeroSize` check in `CGRecordLowering::accumulateFields` and `CGRecordLowering::accumulateBases` to use the `isEmptyXXX` APIs instead, preventing empty fields from being added to the `Members` and `Bases` structures. The rest of the changes fall out from here, to prevent lookups into these structures (for field numbers or base indices) from failing. Added `isEmptyRecordForLayout` and `isEmptyFieldForLayout` (open to better naming suggestions). The main difference to the existing `isEmptyRecord`/`isEmptyField` APIs, is that the `isEmptyXXXForLayout` counterparts don't have special treatment for `unnamed bitfields`/arrays and also treat fields of empty types as if they had `[[no_unique_address]]` (i.e., just like the `AsIfNoUniqueAddr` in `isEmptyField` does).
86 lines
2.8 KiB
C++
86 lines
2.8 KiB
C++
// RUN: %clang_cc1 -std=c++11 -triple armv7-none-eabi -emit-llvm -o - %s | FileCheck %s
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struct X {
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X();
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X(const X&);
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X(const char*);
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~X();
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};
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struct Y {
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int i;
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X x;
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};
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// CHECK: @.compoundliteral = internal global [5 x i32] [i32 1, i32 2, i32 3, i32 4, i32 5], align 4
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// CHECK: @q ={{.*}} global ptr @.compoundliteral, align 4
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// CHECK-LABEL: define{{.*}} i32 @_Z1fv()
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int f() {
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// CHECK: [[LVALUE:%[a-z0-9.]+]] = alloca
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// CHECK-NEXT: [[I:%[a-z0-9]+]] = getelementptr inbounds {{.*}}, ptr [[LVALUE]], i32 0, i32 0
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// CHECK-NEXT: store i32 17, ptr [[I]]
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// CHECK-NEXT: [[X:%[a-z0-9]+]] = getelementptr inbounds {{.*}} [[LVALUE]], i32 4
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// CHECK-NEXT: call noundef ptr @_ZN1XC1EPKc({{.*}}[[X]]
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// CHECK-NEXT: [[I:%[a-z0-9]+]] = getelementptr inbounds {{.*}} [[LVALUE]], i32 0, i32 0
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// CHECK-NEXT: [[RESULT:%[a-z0-9]+]] = load i32, ptr
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// CHECK-NEXT: call noundef ptr @_ZN1YD1Ev
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// CHECK-NEXT: ret i32 [[RESULT]]
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return ((Y){17, "seventeen"}).i;
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}
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// CHECK-LABEL: define{{.*}} i32 @_Z1gv()
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int g() {
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// CHECK: store ptr %{{[a-z0-9.]+}}, ptr [[V:%[a-z0-9.]+]]
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const int (&v)[2] = (int [2]) {1,2};
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// CHECK: [[A:%[a-z0-9.]+]] = load ptr, ptr [[V]]
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// CHECK-NEXT: [[A0ADDR:%[a-z0-9.]+]] = getelementptr inbounds [2 x i32], ptr [[A]], i32 0, {{.*}} 0
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// CHECK-NEXT: [[A0:%[a-z0-9.]+]] = load i32, ptr [[A0ADDR]]
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// CHECK-NEXT: ret i32 [[A0]]
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return v[0];
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}
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// GCC's compound-literals-in-C++ extension lifetime-extends a compound literal
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// (or a C++11 list-initialized temporary!) if:
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// - it is at global scope
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// - it has array type
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// - it has a constant initializer
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struct Z { int i[3]; };
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int *p = (Z){ {1, 2, 3} }.i;
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// CHECK: define {{.*}}__cxx_global_var_init()
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// CHECK: alloca %struct.Z
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// CHECK: store ptr %{{.*}}, ptr @p
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int *q = (int [5]){1, 2, 3, 4, 5};
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// (constant initialization, checked above)
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extern int n;
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int *r = (int [5]){1, 2, 3, 4, 5} + n;
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// CHECK-LABEL: define {{.*}}__cxx_global_var_init.1()
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// CHECK: %[[PTR:.*]] = getelementptr inbounds i32, ptr @.compoundliteral.2, i32 %
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// CHECK: store ptr %[[PTR]], ptr @r
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int *PR21912_1 = (int []){} + n;
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// CHECK-LABEL: define {{.*}}__cxx_global_var_init.3()
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// CHECK: %[[PTR:.*]] = getelementptr inbounds i32, ptr @.compoundliteral.4, i32 %
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// CHECK: store ptr %[[PTR]], ptr @PR21912_1
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union PR21912Ty {
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long long l;
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double d;
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};
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union PR21912Ty *PR21912_2 = (union PR21912Ty[]){{.d = 2.0}, {.l = 3}} + n;
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// CHECK-LABEL: define {{.*}}__cxx_global_var_init.5()
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// CHECK: %[[PTR:.*]] = getelementptr inbounds %union.PR21912Ty, ptr @.compoundliteral.6, i32 %
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// CHECK: store ptr %[[PTR]], ptr @PR21912_2, align 4
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// This compound literal should have local scope.
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int computed_with_lambda = [] {
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int *array = (int[]) { 1, 3, 5, 7 };
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return array[0];
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}();
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// CHECK-LABEL: define internal noundef i32 @{{.*}}clEv
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// CHECK: alloca [4 x i32]
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