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llvm-project/clang/test/CodeGen/uwtable-attr.c

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Extend the `uwtable` attribute with unwind table kind We have the `clang -cc1` command-line option `-funwind-tables=1|2` and the codegen option `VALUE_CODEGENOPT(UnwindTables, 2, 0) ///< Unwind tables (1) or asynchronous unwind tables (2)`. However, this is encoded in LLVM IR by the presence or the absence of the `uwtable` attribute, i.e. we lose the information whether to generate want just some unwind tables or asynchronous unwind tables. Asynchronous unwind tables take more space in the runtime image, I'd estimate something like 80-90% more, as the difference is adding roughly the same number of CFI directives as for prologues, only a bit simpler (e.g. `.cfi_offset reg, off` vs. `.cfi_restore reg`). Or even more, if you consider tail duplication of epilogue blocks. Asynchronous unwind tables could also restrict code generation to having only a finite number of frame pointer adjustments (an example of *not* having a finite number of `SP` adjustments is on AArch64 when untagging the stack (MTE) in some cases the compiler can modify `SP` in a loop). Having the CFI precise up to an instruction generally also means one cannot bundle together CFI instructions once the prologue is done, they need to be interspersed with ordinary instructions, which means extra `DW_CFA_advance_loc` commands, further increasing the unwind tables size. That is to say, async unwind tables impose a non-negligible overhead, yet for the most common use cases (like C++ exceptions), they are not even needed. This patch extends the `uwtable` attribute with an optional value: - `uwtable` (default to `async`) - `uwtable(sync)`, synchronous unwind tables - `uwtable(async)`, asynchronous (instruction precise) unwind tables Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D114543
2022-02-14 21:41:34 +08:00
// Test that function and modules attributes react on the command-line options,
// it does not state the current behaviour makes sense in all cases (it does not).
Fix test failure for targets with varying uwtable defaults Depending on toolchain and ABI, a target might not output DWARF unwind tables by default. Run the test for a target with a known behaviour, test coverage is not reduced. Reviewed By: dmgreen Differential Revision: https://reviews.llvm.org/D119724
2022-02-14 23:50:53 +08:00
// RUN: %clang -target x86_64-linux -S -emit-llvm -o - %s | FileCheck %s -check-prefixes=CHECK,DEFAULT
// RUN: %clang -target x86_64-linux -S -emit-llvm -o - %s -funwind-tables -fno-asynchronous-unwind-tables | FileCheck %s -check-prefixes=CHECK,TABLES
// RUN: %clang -target x86_64-linux -S -emit-llvm -o - %s -fno-unwind-tables -fno-asynchronous-unwind-tables | FileCheck %s -check-prefixes=CHECK,NO_TABLES
Extend the `uwtable` attribute with unwind table kind We have the `clang -cc1` command-line option `-funwind-tables=1|2` and the codegen option `VALUE_CODEGENOPT(UnwindTables, 2, 0) ///< Unwind tables (1) or asynchronous unwind tables (2)`. However, this is encoded in LLVM IR by the presence or the absence of the `uwtable` attribute, i.e. we lose the information whether to generate want just some unwind tables or asynchronous unwind tables. Asynchronous unwind tables take more space in the runtime image, I'd estimate something like 80-90% more, as the difference is adding roughly the same number of CFI directives as for prologues, only a bit simpler (e.g. `.cfi_offset reg, off` vs. `.cfi_restore reg`). Or even more, if you consider tail duplication of epilogue blocks. Asynchronous unwind tables could also restrict code generation to having only a finite number of frame pointer adjustments (an example of *not* having a finite number of `SP` adjustments is on AArch64 when untagging the stack (MTE) in some cases the compiler can modify `SP` in a loop). Having the CFI precise up to an instruction generally also means one cannot bundle together CFI instructions once the prologue is done, they need to be interspersed with ordinary instructions, which means extra `DW_CFA_advance_loc` commands, further increasing the unwind tables size. That is to say, async unwind tables impose a non-negligible overhead, yet for the most common use cases (like C++ exceptions), they are not even needed. This patch extends the `uwtable` attribute with an optional value: - `uwtable` (default to `async`) - `uwtable(sync)`, synchronous unwind tables - `uwtable(async)`, asynchronous (instruction precise) unwind tables Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D114543
2022-02-14 21:41:34 +08:00
Fix test failure for targets with varying uwtable defaults Depending on toolchain and ABI, a target might not output DWARF unwind tables by default. Run the test for a target with a known behaviour, test coverage is not reduced. Reviewed By: dmgreen Differential Revision: https://reviews.llvm.org/D119724
2022-02-14 23:50:53 +08:00
// RUN: %clang -target x86_64-linux -S -emit-llvm -o - -x c++ %s | FileCheck %s -check-prefixes=CHECK,DEFAULT
// RUN: %clang -target x86_64-linux -S -emit-llvm -o - -x c++ %s -funwind-tables -fno-asynchronous-unwind-tables | FileCheck %s -check-prefixes=CHECK,TABLES
// RUN: %clang -target x86_64-linux -S -emit-llvm -o - -x c++ %s -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables | FileCheck %s -check-prefixes=CHECK,NO_TABLES
// REQUIRES: x86-registered-target
Extend the `uwtable` attribute with unwind table kind We have the `clang -cc1` command-line option `-funwind-tables=1|2` and the codegen option `VALUE_CODEGENOPT(UnwindTables, 2, 0) ///< Unwind tables (1) or asynchronous unwind tables (2)`. However, this is encoded in LLVM IR by the presence or the absence of the `uwtable` attribute, i.e. we lose the information whether to generate want just some unwind tables or asynchronous unwind tables. Asynchronous unwind tables take more space in the runtime image, I'd estimate something like 80-90% more, as the difference is adding roughly the same number of CFI directives as for prologues, only a bit simpler (e.g. `.cfi_offset reg, off` vs. `.cfi_restore reg`). Or even more, if you consider tail duplication of epilogue blocks. Asynchronous unwind tables could also restrict code generation to having only a finite number of frame pointer adjustments (an example of *not* having a finite number of `SP` adjustments is on AArch64 when untagging the stack (MTE) in some cases the compiler can modify `SP` in a loop). Having the CFI precise up to an instruction generally also means one cannot bundle together CFI instructions once the prologue is done, they need to be interspersed with ordinary instructions, which means extra `DW_CFA_advance_loc` commands, further increasing the unwind tables size. That is to say, async unwind tables impose a non-negligible overhead, yet for the most common use cases (like C++ exceptions), they are not even needed. This patch extends the `uwtable` attribute with an optional value: - `uwtable` (default to `async`) - `uwtable(sync)`, synchronous unwind tables - `uwtable(async)`, asynchronous (instruction precise) unwind tables Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D114543
2022-02-14 21:41:34 +08:00
#ifdef __cplusplus
extern "C" void g(void);
struct S { ~S(); };
extern "C" int f() { S s; g(); return 0;};
#else
void g(void);
Use functions with prototypes when appropriate; NFC A significant number of our tests in C accidentally use functions without prototypes. This patch converts the function signatures to have a prototype for the situations where the test is not specific to K&R C declarations. e.g., void func(); becomes void func(void); This is the twelfth batch of tests being updated (the end may be in sight soon though).
2022-02-17 05:09:36 +08:00
int f(void) { g(); return 0; };
Extend the `uwtable` attribute with unwind table kind We have the `clang -cc1` command-line option `-funwind-tables=1|2` and the codegen option `VALUE_CODEGENOPT(UnwindTables, 2, 0) ///< Unwind tables (1) or asynchronous unwind tables (2)`. However, this is encoded in LLVM IR by the presence or the absence of the `uwtable` attribute, i.e. we lose the information whether to generate want just some unwind tables or asynchronous unwind tables. Asynchronous unwind tables take more space in the runtime image, I'd estimate something like 80-90% more, as the difference is adding roughly the same number of CFI directives as for prologues, only a bit simpler (e.g. `.cfi_offset reg, off` vs. `.cfi_restore reg`). Or even more, if you consider tail duplication of epilogue blocks. Asynchronous unwind tables could also restrict code generation to having only a finite number of frame pointer adjustments (an example of *not* having a finite number of `SP` adjustments is on AArch64 when untagging the stack (MTE) in some cases the compiler can modify `SP` in a loop). Having the CFI precise up to an instruction generally also means one cannot bundle together CFI instructions once the prologue is done, they need to be interspersed with ordinary instructions, which means extra `DW_CFA_advance_loc` commands, further increasing the unwind tables size. That is to say, async unwind tables impose a non-negligible overhead, yet for the most common use cases (like C++ exceptions), they are not even needed. This patch extends the `uwtable` attribute with an optional value: - `uwtable` (default to `async`) - `uwtable(sync)`, synchronous unwind tables - `uwtable(async)`, asynchronous (instruction precise) unwind tables Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D114543
2022-02-14 21:41:34 +08:00
#endif
// CHECK: define {{.*}} @f() #[[#F:]]
// CHECK: declare {{.*}} @g() #[[#]]
// DEFAULT: attributes #[[#F]] = { {{.*}} uwtable{{ }}{{.*}} }
// DEFAULT: ![[#]] = !{i32 7, !"uwtable", i32 2}
// TABLES: attributes #[[#F]] = { {{.*}} uwtable(sync){{.*}} }
// TABLES: ![[#]] = !{i32 7, !"uwtable", i32 1}
// NO_TABLES-NOT: uwtable