Implement va_arg for Hexagon targets #150008

androm3da · 2025-12-15T01:24:14Z

Implements proper variadic argument handling for hexagon-unknown-linux-musl targets using a 3-pointer VaList structure compatible with LLVM's HexagonBuiltinVaList implementation.

Handles register save area vs overflow area transition
Provides proper 4-byte and 8-byte alignment for arguments
Only activates for hexagon+musl targets via Arch::Hexagon & Env::Musl

rustbot · 2025-12-15T01:24:19Z

r? @lcnr

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androm3da · 2025-12-15T01:28:13Z

cc @folkertdev

Tested with #150009 #150010, and this config.toml:

# Rust build configuration for hexagon-unknown-linux-musl

[build]
# Build the hexagon-unknown-linux-musl target
target = ["x86_64-unknown-linux-gnu", "hexagon-unknown-linux-musl"]

[rust]
# Build the standard library for hexagon-unknown-linux-musl
std = true

# Enable codegen tests to verify the target works
codegen-tests = true

# Use local libc patches
optimize = false

[dist]
# Include the hexagon-unknown-linux-musl target in distributions
missing-tools = true

[target.hexagon-unknown-linux-musl]
# Use hexagon-linux-musl-clang as the linker
cc = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/hexagon-linux-musl-clang"
cxx = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/hexagon-linux-musl-clang++"
linker = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/hexagon-linux-musl-clang"
ar = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/hexagon-linux-musl-ar"
ranlib = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/hexagon-linux-musl-ranlib"
musl-root = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/target/hexagon-unknown-linux-musl/usr"

# Configure qemu-hexagon as the test runner for this target
runner = "/opt/clang+llvm-20.1.4-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/qemu-hexagon"

Implements proper variadic argument handling for hexagon-unknown-linux-musl targets using a 3-pointer VaList structure compatible with LLVM's HexagonBuiltinVaList implementation. * Handles register save area vs overflow area transition * Provides proper 4-byte and 8-byte alignment for arguments * Only activates for hexagon+musl targets via Arch::Hexagon & Env::Musl

rustbot · 2025-12-15T01:55:00Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

lcnr · 2025-12-15T09:17:49Z

@rustbot reroll

folkertdev · 2025-12-15T09:27:23Z

r? folkertdev

folkertdev

On its own this will miscompile, so maybe you can copy the changes from #149967 and just add them to this commit.

View changes since this review

compiler/rustc_codegen_llvm/src/va_arg.rs

androm3da · 2025-12-15T13:38:13Z

On its own this will miscompile, so maybe you can copy the changes from #149967 and just add them to this commit.

View changes since this review

Oh - oops. Or maybe I you can cherry-pick it on top of #149967? No need to make a separate PR if it should just go in that one, I suppose.

folkertdev

I'll just merge this when the other PR is merged then

View changes since this review

folkertdev · 2025-12-16T10:38:35Z

compiler/rustc_codegen_llvm/src/va_arg.rs

+
+    // Calculate offset: round up type size to 4-byte boundary (minimum stack slot size)
+    let type_size = layout.size.bytes();
+    let offset = ((type_size + 3) / 4) * 4; // align to 4 bytes


I believe that is

Suggested change

let offset = ((type_size + 3) / 4) * 4; // align to 4 bytes

let offset = type_size.next_multiple_of(4); // align to 4 bytes

change taken, thanks

folkertdev · 2025-12-16T10:39:54Z

compiler/rustc_codegen_llvm/src/va_arg.rs

+fn emit_hexagon_va_arg_bare_metal<'ll, 'tcx>(
+    bx: &mut Builder<'_, 'll, 'tcx>,
+    list: OperandRef<'tcx, &'ll Value>,
+    target_ty: Ty<'tcx>,
+) -> &'ll Value {


is this different from emit_ptr_va_arg?

Like, I know that this is what LLVM does, but unless I'm missing something LLVM implementation could also use emitVoidPtrVAArg

I think you might be right that clang could use emitVoidPtrVAArg. Do you mind if I take that up separately with the hexagon compiler team and revisit it based on that discussion?

Sounds good.

folkertdev · 2025-12-16T10:40:38Z

compiler/rustc_codegen_llvm/src/va_arg.rs

        // This includes `target.is_like_darwin`, which on x86_64 targets is like sysv64.
        Arch::X86_64 => emit_x86_64_sysv64_va_arg(bx, addr, target_ty),
        Arch::Xtensa => emit_xtensa_va_arg(bx, addr, target_ty),
+        Arch::Hexagon => emit_hexagon_va_arg(bx, addr, target_ty, target.env == Env::Musl),


I'd just inline emit_hexagon_va_arg here

rustbot · 2025-12-17T04:22:59Z

Some changes occurred in src/tools/cargo

cc @ehuss

folkertdev

Nice, thanks!

@bors r+

View changes since this review

folkertdev · 2025-12-17T09:51:48Z

compiler/rustc_codegen_llvm/src/va_arg.rs

+fn emit_hexagon_va_arg_bare_metal<'ll, 'tcx>(
+    bx: &mut Builder<'_, 'll, 'tcx>,
+    list: OperandRef<'tcx, &'ll Value>,
+    target_ty: Ty<'tcx>,
+) -> &'ll Value {


Sounds good.

folkertdev · 2025-12-17T10:00:27Z

@bors r+ rollup

bors · 2025-12-17T10:00:30Z

📌 Commit 4ff4b25 has been approved by folkertdev

It is now in the queue for this repository.

rustbot assigned lcnr Dec 15, 2025

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androm3da force-pushed the bcain/va_arg_rs branch from 961715a to 0c1612e Compare December 15, 2025 01:54

androm3da mentioned this pull request Dec 15, 2025

custom VaList layout for Hexagon #149967

Merged

rustbot assigned SparrowLii and unassigned lcnr Dec 15, 2025

rustbot assigned folkertdev and unassigned SparrowLii Dec 15, 2025

folkertdev reviewed Dec 15, 2025

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compiler/rustc_codegen_llvm/src/va_arg.rs Outdated Show resolved Hide resolved

fixup! Implement va_arg for Hexagon Linux musl targets

d8a0f80

androm3da changed the title ~~Implement va_arg for Hexagon Linux musl targets~~ Implement va_arg for Hexagon targets Dec 16, 2025

folkertdev reviewed Dec 16, 2025

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androm3da force-pushed the bcain/va_arg_rs branch from fa4a020 to 0a956c5 Compare December 17, 2025 04:22

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fixup! Implement va_arg for Hexagon Linux musl targets

4ff4b25

androm3da force-pushed the bcain/va_arg_rs branch from 0a956c5 to 4ff4b25 Compare December 17, 2025 04:26

folkertdev approved these changes Dec 17, 2025

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 17, 2025

	let offset = ((type_size + 3) / 4) * 4; // align to 4 bytes
	let offset = type_size.next_multiple_of(4); // align to 4 bytes

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Implement va_arg for Hexagon targets #150008

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