aganea added inline comments.
================
Comment at: clang/docs/ReleaseNotes.rst:155
+- Add support for MSVC-compatible ``/JMC``/``/JMC-`` flag in clang-cl, and
+ equivalent -cc1 flag ``-fjmc``. ``/JMC`` could only be used when ``/Zi`` or
+ ``/Z7`` is turned on. With this addition, clang-cl can be used in Visual
----------------
hans wrote:
> The cc1 flag is more of an implementation detail, so not sure it's worth
> mentioning in the release notes. Or do we want "clang -fjmc" to work?
@ychen @hans An additional question is whether we want to use the same cc1 flag
for an potential ELF port?
================
Comment at: clang/lib/Driver/ToolChains/Clang.cpp:7458
+ /*Default=*/false)) {
+ if (*EmitCodeView && *DebugInfoKind >=
codegenoptions::DebugInfoConstructor)
+ CmdArgs.push_back("-fjmc");
----------------
hans wrote:
> Why that level specifically and not e.g. *DebugInfoKind > NoDebugInfo?
@hans MSVC does this check too, not sure why.
```
D:\git\llvm-project>cl main.cpp /c /JMC
Microsoft (R) C/C++ Optimizing Compiler Version 19.29.30139 for ARM64
Copyright (C) Microsoft Corporation. All rights reserved.
cl : Command line warning D9007 : '/JMC' requires '/Zi, /ZI or /Z7'; option
ignored
main.cpp
```
================
Comment at: llvm/lib/CodeGen/JMCInstrumenter.cpp:111
+
+void createDefaultCheckFunction(Module &M, const char *CheckFunctionName,
+ bool Is32Bit) {
----------------
hans wrote:
> What's the purpose of the default check function? Doesn't the CRT always
> provide one? (And if it doesn't, will JMC work at all?)
@hans That's what MSVC does, to avoid a linker error if the CRT isn't linked in:
```
D:\git\llvm-project>cat main.cpp
int main() { }
D:\git\llvm-project>cl main.cpp /JMC /Z7 /c
Microsoft (R) C/C++ Optimizing Compiler Version 19.29.30139 for x64
Copyright (C) Microsoft Corporation. All rights reserved.
main.cpp
D:\git\llvm-project>dumpbin /disasm main.obj
Microsoft (R) COFF/PE Dumper Version 14.29.30139.0
Copyright (C) Microsoft Corporation. All rights reserved.
Dump of file main.obj
File Type: COFF OBJECT
main:
0000000000000000: 48 83 EC 28 sub rsp,28h
0000000000000004: 48 8D 0D 00 00 00 lea rcx,[__BB04C4AD_main@cpp]
00
000000000000000B: E8 00 00 00 00 call __CheckForDebuggerJustMyCode
0000000000000010: 33 C0 xor eax,eax
0000000000000012: 48 83 C4 28 add rsp,28h
0000000000000016: C3 ret
__JustMyCode_Default:
0000000000000000: C2 00 00 ret 0
Summary
50 .chks64
228 .debug$S
3EC .debug$T
70 .drectve
1 .msvcjmc
C .pdata
1A .text$mn
8 .xdata
D:\git\llvm-project>dumpbin /all main.obj | grep -B12 -A5 'COMDAT; sym=
__JustMyCode_Default'
SECTION HEADER #5
.text$mn name
0 physical address
0 virtual address
3 size of raw data
438 file pointer to raw data (00000438 to 0000043A)
0 file pointer to relocation table
0 file pointer to line numbers
0 number of relocations
0 number of line numbers
60501020 flags
Code
COMDAT; sym= __JustMyCode_Default
16 byte align
Execute Read
RAW DATA #5
00000000: C2 00 00 □..
```
================
Comment at: llvm/lib/CodeGen/JMCInstrumenter.cpp:157
+ const char *CheckFunctionName = "__CheckForDebuggerJustMyCode";
+ bool Is32Bit = Triple(M.getTargetTriple()).getArch() == Triple::x86;
+
----------------
hans wrote:
> That's a very x86 specific check. What about other targets? (Also the calling
> conventions are x86 specific..)
@ychen Worth nothing that /JMC works on ARM/ARM64 as well. Should we support
that too, not sure that's what @hans is implying?
```
D:\git\llvm-project>cl main.cpp /c /JMC /Z7
Microsoft (R) C/C++ Optimizing Compiler Version 19.29.30139 for ARM64
Copyright (C) Microsoft Corporation. All rights reserved.
main.cpp
D:\git\llvm-project>dumpbin /disasm main.obj
Microsoft (R) COFF/PE Dumper Version 14.29.30139.0
Copyright (C) Microsoft Corporation. All rights reserved.
Dump of file main.obj
File Type: COFF OBJECT
main:
0000000000000000: A9BF7BFD stp fp,lr,[sp,#-0x10]!
0000000000000004: 910003FD mov fp,sp
0000000000000008: 90000008 adrp x8,__BB04C4AD_main@cpp
000000000000000C: 91000100 add x0,x8,__BB04C4AD_main@cpp
0000000000000010: 94000000 bl __CheckForDebuggerJustMyCode
0000000000000014: 52800000 mov w0,#0
0000000000000018: A8C17BFD ldp fp,lr,[sp],#0x10
000000000000001C: D65F03C0 ret
__JustMyCode_Default:
0000000000000000: D65F03C0 ret
Summary
48 .chks64
228 .debug$S
3F0 .debug$T
70 .drectve
1 .msvcjmc
8 .pdata
24 .text$mn
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D118428/new/
https://reviews.llvm.org/D118428
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