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The new experimental calling convention preserve_none is the opposite side of existing preserve_all. It tries to preserve as few general registers as possible. So all general registers are caller saved registers. It can also uses more general registers to pass arguments. This attribute doesn't impact floating-point registers. Floating-point registers still follow the c calling convention. Currently preserve_none is supported on X86-64 only. It changes the c calling convention in following fields: * RSP and RBP are the only preserved general registers, all other general registers are caller saved registers. * We can use [RDI, RSI, RDX, RCX, R8, R9, R11, R12, R13, R14, R15, RAX] to pass arguments. It can improve the performance of hot tailcall chain, because many callee saved registers' save/restore instructions can be removed if the tail functions are using preserve_none. In my experiment in protocol buffer, the parsing functions are improved by 3% to 10%.
49 lines
3.5 KiB
C++
49 lines
3.5 KiB
C++
// RUN: %clang_cc1 %s -triple x86_64-scei-ps4 -DPS4 -fsyntax-only -verify
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// RUN: %clang_cc1 %s -triple x86_64-unknown-linux-gnu -fsyntax-only -verify
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#ifdef PS4
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// PS4 does not support these.
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void __vectorcall func_vc() {} // expected-error {{'__vectorcall' calling convention is not supported for this target}}
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void __regcall func_rc() {} // expected-error {{'__regcall' calling convention is not supported for this target}}
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void __attribute__((vectorcall)) funcA() {} // expected-error {{'vectorcall' calling convention is not supported for this target}}
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void __attribute__((regcall)) funcB() {} // expected-error {{'regcall' calling convention is not supported for this target}}
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void __attribute__((ms_abi)) funcH() {} // expected-error {{'ms_abi' calling convention is not supported for this target}}
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void __attribute__((intel_ocl_bicc)) funcJ() {} // expected-error {{'intel_ocl_bicc' calling convention is not supported for this target}}
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void __attribute__((swiftcall)) funcK() {} // expected-error {{'swiftcall' calling convention is not supported for this target}}
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void __attribute__((swiftasynccall)) funcKK() {} // expected-error {{'swiftasynccall' calling convention is not supported for this target}}
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void __attribute__((pascal)) funcG() {} // expected-error {{'pascal' calling convention is not supported for this target}}
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void __attribute__((preserve_most)) funcL() {} // expected-error {{'preserve_most' calling convention is not supported for this target}}
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void __attribute__((preserve_all)) funcM() {} // expected-error {{'preserve_all' calling convention is not supported for this target}}
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void __attribute__((preserve_none)) funcN() {} // expected-error {{'preserve_none' calling convention is not supported for this target}}
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void __attribute__((stdcall)) funcD() {} // expected-error {{'stdcall' calling convention is not supported for this target}}
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void __attribute__((fastcall)) funcE() {} // expected-error {{'fastcall' calling convention is not supported for this target}}
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void __attribute__((thiscall)) funcF() {} // expected-error {{'thiscall' calling convention is not supported for this target}}
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#else
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void __vectorcall func_vc() {}
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void __regcall func_rc() {}
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void __attribute__((vectorcall)) funcA() {}
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void __attribute__((regcall)) funcB() {}
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void __attribute__((ms_abi)) funcH() {}
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void __attribute__((intel_ocl_bicc)) funcJ() {}
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void __attribute__((swiftcall)) funcK() {}
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void __attribute__((swiftasynccall)) funcKK() {}
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void __attribute__((preserve_most)) funcL() {}
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void __attribute__((preserve_all)) funcM() {}
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void __attribute__((preserve_none)) funcN() {}
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// Same function with different calling conventions. Error with a note pointing to the last decl.
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void __attribute__((preserve_all)) funcR(); // expected-note {{previous declaration is here}}
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void __attribute__((preserve_most)) funcR(); // expected-error {{function declared 'preserve_most' here was previously declared 'preserve_all'}}
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void __attribute__((pascal)) funcG() {} // expected-warning {{'pascal' calling convention is not supported for this target}}
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void __attribute__((stdcall)) funcD() {} // expected-warning {{'stdcall' calling convention is not supported for this target}}
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void __attribute__((fastcall)) funcE() {} // expected-warning {{'fastcall' calling convention is not supported for this target}}
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void __attribute__((thiscall)) funcF() {} // expected-warning {{'thiscall' calling convention is not supported for this target}}
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#endif
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void __attribute__((sysv_abi)) funcI() {}
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void __attribute__((cdecl)) funcC() {}
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