maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/clang/test/CodeGenCXX/debug-info-hotpatch-arm.cpp

Ignoring revisions in .git-blame-ignore-revs. Click here to bypass and see the normal blame view.

27 lines
1.1 KiB
C++
Raw Normal View History

[clang-cl] Support the /HOTPATCH flag This patch adds support for the MSVC /HOTPATCH flag: https://docs.microsoft.com/sv-se/cpp/build/reference/hotpatch-create-hotpatchable-image?view=msvc-170&viewFallbackFrom=vs-2019 The flag is translated to a new -fms-hotpatch flag, which in turn adds a 'patchable-function' attribute for each function in the TU. This is then picked up by the PatchableFunction pass which would generate a TargetOpcode::PATCHABLE_OP of minsize = 2 (which means the target instruction must resolve to at least two bytes). TargetOpcode::PATCHABLE_OP is only implemented for x86/x64. When targetting ARM/ARM64, /HOTPATCH isn't required (instructions are always 2/4 bytes and suitable for hotpatching). Additionally, when using /Z7, we generate a 'hot patchable' flag in the CodeView debug stream, in the S_COMPILE3 record. This flag is then picked up by LLD (or link.exe) and is used in conjunction with the linker /FUNCTIONPADMIN flag to generate extra space before each function, to accommodate for live patching long jumps. Please see: https://github.com/llvm/llvm-project/blob/d703b922961e0d02a5effdd4bfbb23ad50a3cc9f/lld/COFF/Writer.cpp#L1298 The outcome is that we can finally use Live++ or Recode along with clang-cl. NOTE: It seems that MSVC cl.exe always enables /HOTPATCH on x64 by default, although if we did the same I thought we might generate sub-optimal code (if this flag was active by default). Additionally, MSVC always generates a .debug$S section and a S_COMPILE3 record, which Clang doesn't do without /Z7. Therefore, the following MSVC command-line "cl /c file.cpp" would have to be written with Clang such as "clang-cl /c file.cpp /HOTPATCH /Z7" in order to obtain the same result. Depends on D43002, D80833 and D81301 for the full feature. Differential Revision: https://reviews.llvm.org/D116511
2022-01-21 00:04:46 +08:00
// REQUIRES: aarch64-registered-target || arm-registered-target
///
/// Check that using /hotpatch doesn't generate an error.
/// Binaries are always hotpatchable on ARM/ARM64.
///
// RUN: %clang_cl --target=arm-pc-windows-msvc /c /hotpatch /Z7 -- %s 2>&1
// RUN: %clang_cl --target=aarch64-pc-windows-msvc /c /hotpatch /Z7 -- %s 2>&1
///
/// Ensure that we set the hotpatchable flag in the debug information.
///
// RUN: %clang_cl --target=arm-pc-windows-msvc /c /Z7 -o %t.obj -- %s
// RUN: llvm-pdbutil dump -symbols %t.obj | FileCheck %s --check-prefix=HOTPATCH
// RUN: %clang_cl --target=aarch64-pc-windows-msvc /c /Z7 -o %t.obj -- %s
// RUN: llvm-pdbutil dump -symbols %t.obj | FileCheck %s --check-prefix=HOTPATCH
// HOTPATCH: S_COMPILE3 [size = [[#]]]
// HOTPATCH: flags = hot patchable
///
/// Unfortunately we need /Z7, Clang does not systematically generate S_COMPILE3.
///
// RUN: %clang_cl --target=aarch64-pc-windows-msvc /c -o %t.obj -- %s
// RUN: llvm-pdbutil dump -symbols %t.obj | FileCheck %s --check-prefix=NO-HOTPATCH
// NO-HOTPATCH-NOT: flags = hot patchable
int main() {
return 0;
}