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Many platform ABIs have special support for passing aggregates that either just contain a single member of floatint-point type, or else a homogeneous set of members of the same floating-point type. When making this determination, any extra "empty" members of the aggregate type will typically be ignored. However, in C++ (at least in all prior versions), no data member would actually count as empty, even if it's type is an empty record -- it would still be considered to take up at least one byte of space, and therefore make those ABI special cases not apply. This is now changing in C++20, which introduced the [[no_unique_address]] attribute. Members of empty record type, if they also carry this attribute, now do *not* take up any space in the type, and therefore the ABI special cases for single-element or homogeneous aggregates should apply. The C++ Itanium ABI has been updated accordingly, and GCC 10 has added support for this new case. This patch now adds support to LLVM. This is cross-platform; it affects all platforms that use the single-element or homogeneous aggregate ABI special case and implement this using any of the following common subroutines in lib/CodeGen/TargetInfo.cpp: isEmptyField isEmptyRecord isSingleElementStruct isHomogeneousAggregate
60 lines
4.8 KiB
C++
60 lines
4.8 KiB
C++
// RUN: %clang_cc1 -triple s390x-linux-gnu -emit-llvm -x c++ -o - %s | FileCheck %s
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// RUN: %clang_cc1 -triple s390x-linux-gnu -emit-llvm -x c++ -o - %s -mfloat-abi soft \
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// RUN: | FileCheck %s --check-prefix=SOFT-FLOAT
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// Verify that class types are also recognized as float-like aggregate types
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class agg_float_class { float a; };
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class agg_float_class pass_agg_float_class(class agg_float_class arg) { return arg; }
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// CHECK-LABEL: define void @_Z20pass_agg_float_class15agg_float_class(%class.agg_float_class* noalias sret align 4 %{{.*}}, float %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z20pass_agg_float_class15agg_float_class(%class.agg_float_class* noalias sret align 4 %{{.*}}, i32 %{{.*}})
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class agg_double_class { double a; };
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class agg_double_class pass_agg_double_class(class agg_double_class arg) { return arg; }
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// CHECK-LABEL: define void @_Z21pass_agg_double_class16agg_double_class(%class.agg_double_class* noalias sret align 8 %{{.*}}, double %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z21pass_agg_double_class16agg_double_class(%class.agg_double_class* noalias sret align 8 %{{.*}}, i64 %{{.*}})
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// For compatibility with GCC, this structure is passed in an FPR in C++,
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// but passed in a GPR in C (checked in systemz-abi.c).
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struct agg_float_cpp { float a; int : 0; };
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struct agg_float_cpp pass_agg_float_cpp(struct agg_float_cpp arg) { return arg; }
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// CHECK-LABEL: define void @_Z18pass_agg_float_cpp13agg_float_cpp(%struct.agg_float_cpp* noalias sret align 4 %{{.*}}, float %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z18pass_agg_float_cpp13agg_float_cpp(%struct.agg_float_cpp* noalias sret align 4 %{{.*}}, i32 %{{.*}})
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// A field member of empty class type in C++ makes the record nonhomogeneous,
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// unless it is marked as [[no_unique_address]]. This does not apply to arrays.
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struct empty { };
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struct agg_nofloat_empty { float a; empty dummy; };
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struct agg_nofloat_empty pass_agg_nofloat_empty(struct agg_nofloat_empty arg) { return arg; }
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// CHECK-LABEL: define void @_Z22pass_agg_nofloat_empty17agg_nofloat_empty(%struct.agg_nofloat_empty* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z22pass_agg_nofloat_empty17agg_nofloat_empty(%struct.agg_nofloat_empty* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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struct agg_float_empty { float a; [[no_unique_address]] empty dummy; };
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struct agg_float_empty pass_agg_float_empty(struct agg_float_empty arg) { return arg; }
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// CHECK-LABEL: define void @_Z20pass_agg_float_empty15agg_float_empty(%struct.agg_float_empty* noalias sret align 4 %{{.*}}, float %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z20pass_agg_float_empty15agg_float_empty(%struct.agg_float_empty* noalias sret align 4 %{{.*}}, i32 %{{.*}})
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struct agg_nofloat_emptyarray { float a; [[no_unique_address]] empty dummy[3]; };
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struct agg_nofloat_emptyarray pass_agg_nofloat_emptyarray(struct agg_nofloat_emptyarray arg) { return arg; }
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// CHECK-LABEL: define void @_Z27pass_agg_nofloat_emptyarray22agg_nofloat_emptyarray(%struct.agg_nofloat_emptyarray* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z27pass_agg_nofloat_emptyarray22agg_nofloat_emptyarray(%struct.agg_nofloat_emptyarray* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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// And likewise for members of base classes.
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struct noemptybase { empty dummy; };
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struct agg_nofloat_emptybase : noemptybase { float a; };
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struct agg_nofloat_emptybase pass_agg_nofloat_emptybase(struct agg_nofloat_emptybase arg) { return arg; }
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// CHECK-LABEL: define void @_Z26pass_agg_nofloat_emptybase21agg_nofloat_emptybase(%struct.agg_nofloat_emptybase* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z26pass_agg_nofloat_emptybase21agg_nofloat_emptybase(%struct.agg_nofloat_emptybase* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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struct emptybase { [[no_unique_address]] empty dummy; };
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struct agg_float_emptybase : emptybase { float a; };
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struct agg_float_emptybase pass_agg_float_emptybase(struct agg_float_emptybase arg) { return arg; }
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// CHECK-LABEL: define void @_Z24pass_agg_float_emptybase19agg_float_emptybase(%struct.agg_float_emptybase* noalias sret align 4 %{{.*}}, float %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z24pass_agg_float_emptybase19agg_float_emptybase(%struct.agg_float_emptybase* noalias sret align 4 %{{.*}}, i32 %{{.*}})
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struct noemptybasearray { [[no_unique_address]] empty dummy[3]; };
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struct agg_nofloat_emptybasearray : noemptybasearray { float a; };
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struct agg_nofloat_emptybasearray pass_agg_nofloat_emptybasearray(struct agg_nofloat_emptybasearray arg) { return arg; }
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// CHECK-LABEL: define void @_Z31pass_agg_nofloat_emptybasearray26agg_nofloat_emptybasearray(%struct.agg_nofloat_emptybasearray* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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// SOFT-FLOAT-LABEL: define void @_Z31pass_agg_nofloat_emptybasearray26agg_nofloat_emptybasearray(%struct.agg_nofloat_emptybasearray* noalias sret align 4 %{{.*}}, i64 %{{.*}})
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