Rollup merge of #120965 - ChrisDenton:sahf, r=michaelwoerister

Add lahfsahf and prfchw target feature

This adds target features for LAHF/SAHF and PrefetchW. These came up. along with the existing CMPXCHG16b. as [baseline features](https://download.microsoft.com/download/c/1/5/c150e1ca-4a55-4a7e-94c5-bfc8c2e785c5/Windows%2010%20Minimum%20Hardware%20Requirements.pdf) required for x86_64 Windows 10+.

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -213,6 +213,7 @@ pub fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> LLVMFeature<'a> {
         ("x86", "rdrand") => LLVMFeature::new("rdrnd"),
         ("x86", "bmi1") => LLVMFeature::new("bmi"),
         ("x86", "cmpxchg16b") => LLVMFeature::new("cx16"),
+        ("x86", "lahfsahf") => LLVMFeature::new("sahf"),
         ("aarch64", "rcpc2") => LLVMFeature::new("rcpc-immo"),
         ("aarch64", "dpb") => LLVMFeature::new("ccpp"),
         ("aarch64", "dpb2") => LLVMFeature::new("ccdp"),

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -77,6 +77,8 @@ pub fn from_target_feature(
                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
                 Some(sym::csky_target_feature) => rust_features.csky_target_feature,
                 Some(sym::loongarch_target_feature) => rust_features.loongarch_target_feature,
+                Some(sym::lahfsahf_target_feature) => rust_features.lahfsahf_target_feature,
+                Some(sym::prfchw_target_feature) => rust_features.prfchw_target_feature,
                 Some(name) => bug!("unknown target feature gate {}", name),
                 None => true,
             };

compiler/rustc_feature/src/unstable.rs

@@ -301,9 +301,11 @@ declare_features! (
     (unstable, csky_target_feature, "1.73.0", Some(44839)),
     (unstable, ermsb_target_feature, "1.49.0", Some(44839)),
     (unstable, hexagon_target_feature, "1.27.0", Some(44839)),
+    (unstable, lahfsahf_target_feature, "CURRENT_RUSTC_VERSION", Some(44839)),
     (unstable, loongarch_target_feature, "1.73.0", Some(44839)),
     (unstable, mips_target_feature, "1.27.0", Some(44839)),
     (unstable, powerpc_target_feature, "1.27.0", Some(44839)),
+    (unstable, prfchw_target_feature, "CURRENT_RUSTC_VERSION", Some(44839)),
     (unstable, riscv_target_feature, "1.45.0", Some(44839)),
     (unstable, rtm_target_feature, "1.35.0", Some(44839)),
     (unstable, sse4a_target_feature, "1.27.0", Some(44839)),

compiler/rustc_span/src/symbol.rs

@@ -934,6 +934,7 @@ symbols! {
         kreg0,
         label,
         label_break_value,
+        lahfsahf_target_feature,
         lang,
         lang_items,
         large_assignments,
@@ -1242,6 +1243,7 @@ symbols! {
         prelude,
         prelude_import,
         preserves_flags,
+        prfchw_target_feature,
         print_macro,
         println_macro,
         proc_dash_macro: "proc-macro",

compiler/rustc_target/src/target_features.rs

@@ -218,10 +218,12 @@ const X86_ALLOWED_FEATURES: &[(&str, Stability)] = &[
     ("fma", Stable),
     ("fxsr", Stable),
     ("gfni", Unstable(sym::avx512_target_feature)),
+    ("lahfsahf", Unstable(sym::lahfsahf_target_feature)),
     ("lzcnt", Stable),
     ("movbe", Stable),
     ("pclmulqdq", Stable),
     ("popcnt", Stable),
+    ("prfchw", Unstable(sym::prfchw_target_feature)),
     ("rdrand", Stable),
     ("rdseed", Stable),
     ("rtm", Unstable(sym::rtm_target_feature)),

tests/ui/check-cfg/well-known-values.stderr

@@ -143,7 +143,7 @@ warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
 LL |     target_feature = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512er`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512pf`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, `avx512vpopcntdq`, `bf16`, `bmi1`, `bmi2`, `bti`, `bulk-memory`, `c`, `cache`, `cmpxchg16b`, `crc`, `crt-static`, `d`, `d32`, `dit`, `doloop`, `dotprod`, `dpb`, `dpb2`, `dsp`, `dsp1e2`, `dspe60`, `e`, `e1`, `e2`, `edsp`, `elrw`, `ermsb`, `exception-handling`, `f`, `f16c`, `f32mm`, `f64mm`, `fast-unaligned-access`, `fcma`, `fdivdu`, `fhm`, `flagm`, `float1e2`, `float1e3`, `float3e4`, `float7e60`, `floate1`, `fma`, `fp-armv8`, `fp16`, `fp64`, `fpuv2_df`, `fpuv2_sf`, `fpuv3_df`, `fpuv3_hf`, `fpuv3_hi`, `fpuv3_sf`, `frintts`, `fxsr`, `gfni`, `hard-float`, `hard-float-abi`, `hard-tp`, `high-registers`, `hvx`, `hvx-length128b`, `hwdiv`, `i8mm`, `jsconv`, `lasx`, `lbt`, `lor`, `lse`, `lsx`, `lvz`, `lzcnt`, `m`, `mclass`, `movbe`, `mp`, `mp1e2`, `msa`, `mte`, `multivalue`, `mutable-globals`, `neon`, `nontrapping-fptoint`, `nvic`, `paca`, `pacg`, `pan`, `pclmulqdq`, `pmuv3`, `popcnt`, `power10-vector`, `power8-altivec`, `power8-vector`, `power9-altivec`, `power9-vector`, `rand`, `ras`, `rclass`, `rcpc`, `rcpc2`, `rdm`, `rdrand`, `rdseed`, `reference-types`, `relax`, `relaxed-simd`, `rtm`, `sb`, `sha`, `sha2`, `sha3`, `sign-ext`, `simd128`, `sm4`, `spe`, `ssbs`, `sse`, `sse2`, `sse3`, `sse4.1`, `sse4.2`, `sse4a`, `ssse3`, `sve`, `sve2`, `sve2-aes`, `sve2-bitperm`, `sve2-sha3`, `sve2-sm4`, `tbm`, `thumb-mode`, `thumb2`, `tme`, `trust`, `trustzone`, `ual`, `v`, `v5te`, `v6`, `v6k`, `v6t2`, `v7`, `v8`, `v8.1a`, `v8.2a`, `v8.3a`, `v8.4a`, `v8.5a`, `v8.6a`, `v8.7a`, `vaes`, `vdsp2e60f`, `vdspv1`, `vdspv2`, `vfp2`, `vfp3`, `vfp4`, `vh`, `virt`, `virtualization`, `vpclmulqdq`, `vsx`, `xsave`, `xsavec`, `xsaveopt`, `xsaves`, `zba`, `zbb`, `zbc`, `zbkb`, `zbkc`, `zbkx`, `zbs`, `zdinx`, `zfh`, `zfhmin`, `zfinx`, `zhinx`, `zhinxmin`, `zk`, `zkn`, `zknd`, `zkne`, `zknh`, `zkr`, `zks`, `zksed`, `zksh`, `zkt`
+   = note: expected values for `target_feature` are: `10e60`, `2e3`, `3e3r1`, `3e3r2`, `3e3r3`, `3e7`, `7e10`, `a`, `aclass`, `adx`, `aes`, `altivec`, `alu32`, `atomics`, `avx`, `avx2`, `avx512bf16`, `avx512bitalg`, `avx512bw`, `avx512cd`, `avx512dq`, `avx512er`, `avx512f`, `avx512fp16`, `avx512ifma`, `avx512pf`, `avx512vbmi`, `avx512vbmi2`, `avx512vl`, `avx512vnni`, `avx512vp2intersect`, `avx512vpopcntdq`, `bf16`, `bmi1`, `bmi2`, `bti`, `bulk-memory`, `c`, `cache`, `cmpxchg16b`, `crc`, `crt-static`, `d`, `d32`, `dit`, `doloop`, `dotprod`, `dpb`, `dpb2`, `dsp`, `dsp1e2`, `dspe60`, `e`, `e1`, `e2`, `edsp`, `elrw`, `ermsb`, `exception-handling`, `f`, `f16c`, `f32mm`, `f64mm`, `fast-unaligned-access`, `fcma`, `fdivdu`, `fhm`, `flagm`, `float1e2`, `float1e3`, `float3e4`, `float7e60`, `floate1`, `fma`, `fp-armv8`, `fp16`, `fp64`, `fpuv2_df`, `fpuv2_sf`, `fpuv3_df`, `fpuv3_hf`, `fpuv3_hi`, `fpuv3_sf`, `frintts`, `fxsr`, `gfni`, `hard-float`, `hard-float-abi`, `hard-tp`, `high-registers`, `hvx`, `hvx-length128b`, `hwdiv`, `i8mm`, `jsconv`, `lahfsahf`, `lasx`, `lbt`, `lor`, `lse`, `lsx`, `lvz`, `lzcnt`, `m`, `mclass`, `movbe`, `mp`, `mp1e2`, `msa`, `mte`, `multivalue`, `mutable-globals`, `neon`, `nontrapping-fptoint`, `nvic`, `paca`, `pacg`, `pan`, `pclmulqdq`, `pmuv3`, `popcnt`, `power10-vector`, `power8-altivec`, `power8-vector`, `power9-altivec`, `power9-vector`, `prfchw`, `rand`, `ras`, `rclass`, `rcpc`, `rcpc2`, `rdm`, `rdrand`, `rdseed`, `reference-types`, `relax`, `relaxed-simd`, `rtm`, `sb`, `sha`, `sha2`, `sha3`, `sign-ext`, `simd128`, `sm4`, `spe`, `ssbs`, `sse`, `sse2`, `sse3`, `sse4.1`, `sse4.2`, `sse4a`, `ssse3`, `sve`, `sve2`, `sve2-aes`, `sve2-bitperm`, `sve2-sha3`, `sve2-sm4`, `tbm`, `thumb-mode`, `thumb2`, `tme`, `trust`, `trustzone`, `ual`, `v`, `v5te`, `v6`, `v6k`, `v6t2`, `v7`, `v8`, `v8.1a`, `v8.2a`, `v8.3a`, `v8.4a`, `v8.5a`, `v8.6a`, `v8.7a`, `vaes`, `vdsp2e60f`, `vdspv1`, `vdspv2`, `vfp2`, `vfp3`, `vfp4`, `vh`, `virt`, `virtualization`, `vpclmulqdq`, `vsx`, `xsave`, `xsavec`, `xsaveopt`, `xsaves`, `zba`, `zbb`, `zbc`, `zbkb`, `zbkc`, `zbkx`, `zbs`, `zdinx`, `zfh`, `zfhmin`, `zfinx`, `zhinx`, `zhinxmin`, `zk`, `zkn`, `zknd`, `zkne`, `zknh`, `zkr`, `zks`, `zksed`, `zksh`, `zkt`
    = note: see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`

tests/ui/target-feature/gate.rs

@@ -19,6 +19,8 @@
 // gate-test-aarch64_ver_target_feature
 // gate-test-csky_target_feature
 // gate-test-loongarch_target_feature
+// gate-test-lahfsahf_target_feature
+// gate-test-prfchw_target_feature
 
 #[target_feature(enable = "avx512bw")]
 //~^ ERROR: currently unstable

tests/ui/target-feature/gate.stderr

@@ -1,5 +1,5 @@
 error[E0658]: the target feature `avx512bw` is currently unstable
-  --> $DIR/gate.rs:23:18
+  --> $DIR/gate.rs:25:18
    |
 LL | #[target_feature(enable = "avx512bw")]
    |                  ^^^^^^^^^^^^^^^^^^^