Wasm Relaxed SIMD intrinsics need new names for LLVM 16

[alexcrichton]

As pointed out here and discovered here the relaxed simd intrinsics for wasm added in https://github.com/rust-lang/stdarch/pull/1393 don't compile with LLVM 16 due to the intrinsics in LLVM being renamed. The patch needed to get the test suite working again is:

diff --git a/crates/core_arch/src/wasm32/relaxed_simd.rs b/crates/core_arch/src/wasm32/relaxed_simd.rs
index 8fe935d1..ae8346aa 100644
--- a/crates/core_arch/src/wasm32/relaxed_simd.rs
+++ b/crates/core_arch/src/wasm32/relaxed_simd.rs
@@ -17,22 +17,22 @@ extern "C" {
     #[link_name = "llvm.wasm.relaxed.trunc.unsigned.zero"]
     fn llvm_relaxed_trunc_unsigned_zero(a: simd::f64x2) -> simd::i32x4;

-    #[link_name = "llvm.wasm.fma.v4f32"]
+    #[link_name = "llvm.wasm.relaxed.madd.v4f32"]
     fn llvm_f32x4_fma(a: simd::f32x4, b: simd::f32x4, c: simd::f32x4) -> simd::f32x4;
-    #[link_name = "llvm.wasm.fms.v4f32"]
+    #[link_name = "llvm.wasm.relaxed.nmadd.v4f32"]
     fn llvm_f32x4_fms(a: simd::f32x4, b: simd::f32x4, c: simd::f32x4) -> simd::f32x4;
-    #[link_name = "llvm.wasm.fma.v2f64"]
+    #[link_name = "llvm.wasm.relaxed.madd.v2f64"]
     fn llvm_f64x2_fma(a: simd::f64x2, b: simd::f64x2, c: simd::f64x2) -> simd::f64x2;
-    #[link_name = "llvm.wasm.fms.v2f64"]
+    #[link_name = "llvm.wasm.relaxed.nmadd.v2f64"]
     fn llvm_f64x2_fms(a: simd::f64x2, b: simd::f64x2, c: simd::f64x2) -> simd::f64x2;

-    #[link_name = "llvm.wasm.laneselect.v16i8"]
+    #[link_name = "llvm.wasm.relaxed.laneselect.v16i8"]
     fn llvm_i8x16_laneselect(a: simd::i8x16, b: simd::i8x16, c: simd::i8x16) -> simd::i8x16;
-    #[link_name = "llvm.wasm.laneselect.v8i16"]
+    #[link_name = "llvm.wasm.relaxed.laneselect.v8i16"]
     fn llvm_i16x8_laneselect(a: simd::i16x8, b: simd::i16x8, c: simd::i16x8) -> simd::i16x8;
-    #[link_name = "llvm.wasm.laneselect.v4i32"]
+    #[link_name = "llvm.wasm.relaxed.laneselect.v4i32"]
     fn llvm_i32x4_laneselect(a: simd::i32x4, b: simd::i32x4, c: simd::i32x4) -> simd::i32x4;
-    #[link_name = "llvm.wasm.laneselect.v2i64"]
+    #[link_name = "llvm.wasm.relaxed.laneselect.v2i64"]
     fn llvm_i64x2_laneselect(a: simd::i64x2, b: simd::i64x2, c: simd::i64x2) -> simd::i64x2;

     #[link_name = "llvm.wasm.relaxed.min.v4f32"]
@@ -46,9 +46,9 @@ extern "C" {

     #[link_name = "llvm.wasm.relaxed.q15mulr.signed"]
     fn llvm_relaxed_q15mulr_signed(a: simd::i16x8, b: simd::i16x8) -> simd::i16x8;
-    #[link_name = "llvm.wasm.dot.i8x16.i7x16.signed"]
+    #[link_name = "llvm.wasm.relaxed.dot.i8x16.i7x16.signed"]
     fn llvm_i16x8_relaxed_dot_i8x16_i7x16_s(a: simd::i8x16, b: simd::i8x16) -> simd::i16x8;
-    #[link_name = "llvm.wasm.dot.i8x16.i7x16.add.signed"]
+    #[link_name = "llvm.wasm.relaxed.dot.i8x16.i7x16.add.signed"]
     fn llvm_i32x4_relaxed_dot_i8x16_i7x16_add_s(
         a: simd::i8x16,
         b: simd::i8x16,

but @Amanieu I wanted to ask, is there a means by which nowadays the intrinsics can have conditional definitions based on the LLVM version used? It looks like the current Rust nightly reverted back to LLVM 15 so this patch can't land on the main branch right now. I'd be happy to adjust with #[cfg_attr], though, if there's selectors for the LLVM version.

[thomcc]

There's no cfg currently passed for LLVM version, although I think we've been through something similar before which we solved using a new llvm14-builtins-abi target feature (but perhaps I misunderstood what that was for).

[nikic]

This is an LLVM bug: Missing autoupgrade for the intrinsic renames.

For reference, the buggy patch was https://reviews.llvm.org/D138249.

[Amanieu]

llvm14-builtins-abi was for compiler-builtins, not stdarch. In general stdarch is extremely sensitive to the LLVM version since it directly binds to LLVM intrinsics. It is difficult to support anything other than the "current" LLVM version used by rustc.

[alexcrichton]

Ok sounds like I'll wait for the LLVM 16 update to re-land and then I can send a PR with the above changes

[nikic]

Upstream fix: https://reviews.llvm.org/D146424