Remove i586-pc-windows-msvc

See MCP 840.

I left a specialized error message that should help users that hit this
in the wild (for example, because they use it in their CI).

compiler/rustc_target/src/spec/mod.rs

@@ -1915,7 +1915,6 @@ supported_targets! {
     ("i686-pc-windows-msvc", i686_pc_windows_msvc),
     ("i686-uwp-windows-msvc", i686_uwp_windows_msvc),
     ("i686-win7-windows-msvc", i686_win7_windows_msvc),
-    ("i586-pc-windows-msvc", i586_pc_windows_msvc),
     ("thumbv7a-pc-windows-msvc", thumbv7a_pc_windows_msvc),
     ("thumbv7a-uwp-windows-msvc", thumbv7a_uwp_windows_msvc),
 
@@ -3503,7 +3502,15 @@ impl Target {
                     return load_file(&p);
                 }
 
-                Err(format!("Could not find specification for target {target_tuple:?}"))
+                // Leave in a specialized error message for the removed target.
+                // FIXME: If you see this and it's been a few months after this has been released,
+                // you can probably remove it.
+                if target_tuple == "i586-pc-windows-msvc" {
+                    Err("the `i586-pc-windows-msvc` target has been removed. Use the `i686-pc-windows-msvc` target instead.\n\
+                        Windows 10 (the minimum required OS version) requires a CPU baseline of at least i686 so you can safely switch".into())
+                } else {
+                    Err(format!("Could not find specification for target {target_tuple:?}"))
+                }
             }
             TargetTuple::TargetJson { ref contents, .. } => {
                 let obj = serde_json::from_str(contents).map_err(|e| e.to_string())?;

src/ci/github-actions/jobs.yml

@@ -591,7 +591,7 @@ auto:
       RUST_CONFIGURE_ARGS: >-
         --build=i686-pc-windows-msvc
         --host=i686-pc-windows-msvc
-        --target=i686-pc-windows-msvc,i586-pc-windows-msvc
+        --target=i686-pc-windows-msvc
         --enable-full-tools
         --enable-profiler
       SCRIPT: python x.py dist bootstrap --include-default-paths

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

@@ -162,7 +162,6 @@ target | std | notes
 [`armv7a-none-eabi`](platform-support/arm-none-eabi.md) | * | Bare Armv7-A
 [`armv7r-none-eabi`](platform-support/armv7r-none-eabi.md) | * | Bare Armv7-R
 [`armv7r-none-eabihf`](platform-support/armv7r-none-eabi.md) | * | Bare Armv7-R, hardfloat
-`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 ([Pentium 4 plus various extensions](https://developer.android.com/ndk/guides/abis.html#x86)) [^x86_32-floats-return-ABI]

src/tools/build-manifest/src/main.rs

@@ -97,7 +97,6 @@ static TARGETS: &[&str] = &[
     "bpfeb-unknown-none",
     "bpfel-unknown-none",
     "i386-apple-ios",
-    "i586-pc-windows-msvc",
     "i586-unknown-linux-gnu",
     "i586-unknown-linux-musl",
     "i586-unknown-redox",

tests/assembly/stack-protector/stack-protector-target-support.rs

@@ -3,7 +3,7 @@
 //
 //@ add-core-stubs
 //@ revisions: r1 r2 r3 r4 r5 r6 r7 r8 r9 r10 r11 r12 r13 r14 r15 r16 r17 r18 r19 r20 r21 r22 r23
-//@ revisions: r24 r25 r26 r27 r28 r29 r30 r31 r32 r33     r35 r36 r37 r38 r39 r40 r41 r42 r43 r44
+//@ revisions: r24 r25 r26 r27 r28 r29 r30 r31 r32 r33         r36 r37 r38 r39 r40 r41 r42 r43 r44
 //@ revisions: r45 r46 r47 r48 r49 r50 r51 r52 r53 r54 r55 r56 r57 r58 r59 r60 r61 r62 r63 r64 r65
 //@ revisions: r66 r67 r68 r69 r70 r71 r72 r73 r74 r75 r76 r77 r78 r79 r80 r81 r82 r83 r84 r85
 //@ assembly-output: emit-asm
@@ -73,9 +73,6 @@
 //@ [r32] needs-llvm-components: arm
 //@ [r33] compile-flags: --target armv7-unknown-linux-musleabihf
 //@ [r33] needs-llvm-components: arm
-
-//@ [r35] compile-flags: --target i586-pc-windows-msvc
-//@ [r35] needs-llvm-components: x86
 //@ [r36] compile-flags: --target i586-unknown-linux-gnu
 //@ [r36] needs-llvm-components: x86
 //@ [r37] compile-flags: --target i586-unknown-linux-musl
@@ -195,7 +192,6 @@ pub fn foo() {
     // r3: calll @__security_check_cookie
     // r7: callq __security_check_cookie
     // r13: bl __security_check_cookie
-    // r35: calll @__security_check_cookie
 
     // cuda doesn't support stack-smash protection
     // r49-NOT: __security_check_cookie

tests/assembly/targets/targets-pe.rs

@@ -25,9 +25,6 @@
 //@ revisions: bpfel_unknown_none
 //@ [bpfel_unknown_none] compile-flags: --target bpfel-unknown-none
 //@ [bpfel_unknown_none] needs-llvm-components: bpf
-//@ revisions: i586_pc_windows_msvc
-//@ [i586_pc_windows_msvc] compile-flags: --target i586-pc-windows-msvc
-//@ [i586_pc_windows_msvc] needs-llvm-components: x86
 //@ revisions: i686_pc_windows_gnu
 //@ [i686_pc_windows_gnu] compile-flags: --target i686-pc-windows-gnu
 //@ [i686_pc_windows_gnu] needs-llvm-components: x86