@llvm.experimental.stackmap intrinsic crashes when the second parameter (numShadowBytes) is a variable instead of a constant

[DigOrDog]

Description

The llvm.experimental.stackmap intrinsic currently crashes when the numShadowBytes parameter is provided as a variable rather than a constant. According to the syntax, llvm.experimental.stackmap is expected to record the location of specified values in the stack map without generating code. However, when attempting to pass a variable as the second argument (numShadowBytes), the compiler fails, leading to a segmentation fault during the X86 DAG->DAG Instruction Selection pass.

Example code that triggers the crash:

@G = global i16 0
@G.1 = global i32 2147483647

define void @f(i32 %nelems) {
entry:
  %B = sub i32 %nelems, 65536
  %mem = alloca i32, i32 %nelems, align 4
  call void (i64, i32, ...) @llvm.experimental.stackmap(i64 0, i32 %B, ptr %mem)
  ret void
}

; Function Attrs: nocallback nofree nosync willreturn
declare void @llvm.experimental.stackmap(i64, i32, ...) #0

attributes #0 = { nocallback nofree nosync willreturn }

https://godbolt.org/z/eM46jdv7r

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: None (DigOrDog)

# Description The llvm.experimental.stackmap intrinsic currently crashes when the numShadowBytes parameter is provided as a variable rather than a constant. According to the syntax, llvm.experimental.stackmap is expected to record the location of specified values in the stack map without generating code. However, when attempting to pass a variable as the second argument (numShadowBytes), the compiler fails, leading to a segmentation fault during the X86 DAG->DAG Instruction Selection pass.

Example code that triggers the crash:

@<!-- -->G = global i16 0
@<!-- -->G.1 = global i32 2147483647

define void @<!-- -->f(i32 %nelems) {
entry:
  %B = sub i32 %nelems, 65536
  %mem = alloca i32, i32 %nelems, align 4
  call void (i64, i32, ...) @<!-- -->llvm.experimental.stackmap(i64 0, i32 %B, ptr %mem)
  ret void
}

; Function Attrs: nocallback nofree nosync willreturn
declare void @<!-- -->llvm.experimental.stackmap(i64, i32, ...) #<!-- -->0

attributes #<!-- -->0 = { nocallback nofree nosync willreturn }

https://godbolt.org/z/eM46jdv7r

[phoebewang]

The backtrace shows the problem is in generic codegen. I think we just need to add ImmArg<ArgIndex<0>, ImmArg<ArgIndex<1> to int_experimental_stackmap/

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: None (DigOrDog)

# Description The llvm.experimental.stackmap intrinsic currently crashes when the numShadowBytes parameter is provided as a variable rather than a constant. According to the syntax, llvm.experimental.stackmap is expected to record the location of specified values in the stack map without generating code. However, when attempting to pass a variable as the second argument (numShadowBytes), the compiler fails, leading to a segmentation fault during the X86 DAG->DAG Instruction Selection pass.

Example code that triggers the crash:

@<!-- -->G = global i16 0
@<!-- -->G.1 = global i32 2147483647

define void @<!-- -->f(i32 %nelems) {
entry:
  %B = sub i32 %nelems, 65536
  %mem = alloca i32, i32 %nelems, align 4
  call void (i64, i32, ...) @<!-- -->llvm.experimental.stackmap(i64 0, i32 %B, ptr %mem)
  ret void
}

; Function Attrs: nocallback nofree nosync willreturn
declare void @<!-- -->llvm.experimental.stackmap(i64, i32, ...) #<!-- -->0

attributes #<!-- -->0 = { nocallback nofree nosync willreturn }

https://godbolt.org/z/eM46jdv7r

[Atafid]

Hello,
I am new to contributing to LLVM, but I would like to try working on this if possible :)

[kmr-srbh]

Hello @Atafid! Are you working on this?