Rollup merge of rust-lang#136885 - RalfJung:linux-android-base-cpu, r=jieyouxu

i686-linux-android: increase CPU baseline to Pentium 4 (without an actual change

As per `@maurer's` [comment](rust-lang#136495 (comment)), this shouldn't actually change anything since we anyway add a bunch of extensions that bump things up way beyond Pentium 4. But Pentium 4 is consistent with the other i686 targets and I don't know enough about the exact sequence of CPU generations to be confident with more than this. ;)

Author: matthiaskrgr

compiler/rustc_target/src/spec/targets/i686_linux_android.rs

@@ -9,7 +9,7 @@ pub(crate) fn target() -> Target {
     base.max_atomic_width = Some(64);
 
     // https://developer.android.com/ndk/guides/abis.html#x86
-    base.cpu = "pentiumpro".into();
+    base.cpu = "pentium4".into();
     base.features = "+mmx,+sse,+sse2,+sse3,+ssse3".into();
     base.stack_probes = StackProbeType::Inline;
 

src/doc/rustc/src/platform-support.md

@@ -165,7 +165,7 @@ target | std | notes
 `i586-pc-windows-msvc` | * | 32-bit Windows (original Pentium) [^x86_32-floats-x87]
 `i586-unknown-linux-gnu` | ✓ | 32-bit Linux (kernel 3.2, glibc 2.17, original Pentium) [^x86_32-floats-x87]
 `i586-unknown-linux-musl` | ✓ | 32-bit Linux (musl 1.2.3, original Pentium) [^x86_32-floats-x87]
-[`i686-linux-android`](platform-support/android.md) | ✓ | 32-bit x86 Android ([PentiumPro with SSE](https://developer.android.com/ndk/guides/abis.html#x86)) [^x86_32-floats-return-ABI]
+[`i686-linux-android`](platform-support/android.md) | ✓ | 32-bit x86 Android ([Pentium 4 plus various extensions](https://developer.android.com/ndk/guides/abis.html#x86)) [^x86_32-floats-return-ABI]
 [`i686-pc-windows-gnullvm`](platform-support/pc-windows-gnullvm.md) | ✓ | 32-bit x86 MinGW (Windows 10+, Pentium 4), LLVM ABI [^x86_32-floats-return-ABI]
 [`i686-unknown-freebsd`](platform-support/freebsd.md) | ✓ | 32-bit x86 FreeBSD (Pentium 4) [^x86_32-floats-return-ABI]
 `i686-unknown-linux-musl` | ✓ | 32-bit Linux with musl 1.2.3 (Pentium 4) [^x86_32-floats-return-ABI]