| Issue |
163454
|
| Summary |
[Docs][Intrisics] LLVM intrisics documentation use wrong `llvm.memset.inline` variants
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
niooss-ledger
|
Hello,
Since `llvm.memset.inline` was introduced (commit https://github.com/llvm/llvm-project/commit/38637ee477541370a90b37f149069d8e5c0c2efd), its documentation on https://llvm.org/docs/LangRef.html#llvm-memset-inline-intrinsic contains:
```text
declare void @llvm.memset.inline.p0.p0i8.i32(ptr <dest>, i8 <val>,
i32 <len>, i1 <isvolatile>)
declare void @llvm.memset.inline.p0.p0.i64(ptr <dest>, i8 <val>,
i64 <len>, i1 <isvolatile>)
```
Using `p0i8` and `p0.p0` in the names seems strange. Actually, this is not what `clang` generates. Indeed, when `clang` compiles `__builtin_memset_inline`, it produces `@llvm.memset.inline.p0.i64`. There already is a test for this: https://github.com/llvm/llvm-project/blob/20bcf123e2db033f208462f34f63e292efbe0946/clang/test/CodeGen/builtins-memset-inline.c#L6-L9
Moreover, even when compiling in 32-bit mode (using `clang -target i686-unknown-linux -S -emit-llvm clang/test/CodeGen/builtins-memset-inline.c -o -`) produces calls to `@llvm.memset.inline.p0.i64`, not `....p0.i32`. The 32-bit variant seems to be accepted by the LLVM IR compiler anyway:
```console
$ cat builtins-memset-inline.ll
target triple = "i686-unknown-linux"
; Function Attrs: noinline nounwind optnone uwtable
define dso_local void @test_memset_inline_4(ptr noundef %0, i8 noundef signext %1) #0 {
call void @llvm.memset.inline.p0.i32(ptr align 1 %0, i8 %1, i32 4, i1 false)
ret void
}
; Function Attrs: nocallback nofree nounwind willreturn memory(argmem: write)
declare void @llvm.memset.inline.p0.i32(ptr nocapture writeonly, i8, i32, i1 immarg) #1
$ clang -O2 -target i686-unknown-linux -S builtins-memset-inline.ll -o -
.file "builtins-memset-inline.ll"
.text
.globl test_memset_inline_4 # -- Begin function test_memset_inline_4
.p2align 4
.type test_memset_inline_4,@function
test_memset_inline_4: # @test_memset_inline_4
# %bb.0:
movzbl 8(%esp), %ecx
movl 4(%esp), %eax
imull $16843009, %ecx, %ecx # imm = 0x1010101
movl %ecx, (%eax)
retl
.Lfunc_end0:
.size test_memset_inline_4, .Lfunc_end0-test_memset_inline_4
# -- End function
.section ".note.GNU-stack","",@progbits
.addrsig
```
(The call to `@llvm.memset.inline.p0.i32` was correctly inlined to `imull $16843009, %ecx, %ecx` and `movl %ecx, (%eax)`)
In short, I believe there are 2 possible issues:
1. The documentation of `llvm.memset.inline`' intrinsics contain functions with the wrong names: https://github.com/llvm/llvm-project/blob/20bcf123e2db033f208462f34f63e292efbe0946/llvm/docs/LangRef.rst#L16013-L16016
2. When compiling a C program in 32-bit mode, `@llvm.memset.inline.p0.i64` is generated instead of `@llvm.memset.inline.p0.i32`.
What do you think?
In case it is useful, I used several released versions of `clang` to reproduce the tests, including clang 20.1.8 (0ubuntu4) on Ubuntu 25.10 and clang 21.1.3 (Fedora 21.1.3-1.fc44) on Fedora 44.
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