From f4a7b5b81c938a1638cb5265b6ad485a9bf5b785 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=BCnther=20Brammer?= <gbrammer@gmx.de>
Date: Mon, 9 Oct 2023 00:52:28 +0200
Subject: [PATCH 1/2] Override -C target-feature with features implied by
 --target

Change the features enabled by various target specifications from defaults
to mandatory features. This will be used to prevent -C target-feature=-x87
and -C target-feature=-sse from changing the ABI on x86.
---
 compiler/rustc_codegen_llvm/src/llvm_util.rs | 38 ++++++++++----------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index a76c9c9b7356c..5b459cd18e307 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -459,23 +459,25 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
     // Features that come earlier are overridden by conflicting features later in the string.
     // Typically we'll want more explicit settings to override the implicit ones, so:
     //
+    // * Features disabled by --target; are overridden by
     // * Features from -Ctarget-cpu=*; are overridden by [^1]
-    // * Features implied by --target; are overridden by
     // * Features from -Ctarget-feature; are overridden by
+    // * Features implied by --target; are overridden by
     // * function specific features.
     //
     // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly
     // through LLVM TargetMachine implementation.
-    //
-    // FIXME(nagisa): it isn't clear what's the best interaction between features implied by
-    // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always
-    // override anything that's implicit, so e.g. when there's no `--target` flag, features implied
-    // the host target are overridden by `-Ctarget-cpu=*`. On the other hand, what about when both
-    // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both
-    // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence
-    // should be taken in cases like these.
     let mut features = vec![];
 
+    // Features disabled by an implicit or explicit `--target`.
+    features.extend(
+        sess.target
+            .features
+            .split(',')
+            .filter(|v| !v.is_empty() && backend_feature_name(v).is_some() && v.starts_with("-"))
+            .map(String::from),
+    );
+
     // -Ctarget-cpu=native
     match sess.opts.cg.target_cpu {
         Some(ref s) if s == "native" => {
@@ -501,15 +503,6 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
         Some(_) | None => {}
     };
 
-    // Features implied by an implicit or explicit `--target`.
-    features.extend(
-        sess.target
-            .features
-            .split(',')
-            .filter(|v| !v.is_empty() && backend_feature_name(v).is_some())
-            .map(String::from),
-    );
-
     // -Ctarget-features
     let supported_features = supported_target_features(sess);
     let mut featsmap = FxHashMap::default();
@@ -583,6 +576,15 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
         .flatten();
     features.extend(feats);
 
+    // Features implied by an implicit or explicit `--target`.
+    features.extend(
+        sess.target
+            .features
+            .split(',')
+            .filter(|v| !v.is_empty() && backend_feature_name(v).is_some() && v.starts_with("+"))
+            .map(String::from),
+    );
+
     if diagnostics && let Some(f) = check_tied_features(sess, &featsmap) {
         sess.emit_err(TargetFeatureDisableOrEnable {
             features: f,

From 66625a9e2ae812f9a0bc1b3c6d7f4008b8bba619 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=BCnther=20Brammer?= <gbrammer@gmx.de>
Date: Mon, 9 Oct 2023 01:21:33 +0200
Subject: [PATCH 2/2] Make x87, sse and sse2 mandatory on targets enabling them

These features enable registers that are or will be used in the ABI.
Instead of only being implied by the target cpu, they are now explicitly
enabled so that they cannot be disabled by -C target-feature.
---
 compiler/rustc_target/src/spec/i386_apple_ios.rs          | 1 +
 compiler/rustc_target/src/spec/i386_unknown_linux_gnu.rs  | 1 +
 compiler/rustc_target/src/spec/i486_unknown_linux_gnu.rs  | 1 +
 compiler/rustc_target/src/spec/i586_pc_nto_qnx700.rs      | 1 +
 compiler/rustc_target/src/spec/i586_pc_windows_msvc.rs    | 1 +
 compiler/rustc_target/src/spec/i586_unknown_linux_gnu.rs  | 1 +
 compiler/rustc_target/src/spec/i586_unknown_linux_musl.rs | 1 +
 compiler/rustc_target/src/spec/i686_apple_darwin.rs       | 1 +
 compiler/rustc_target/src/spec/i686_linux_android.rs      | 2 +-
 compiler/rustc_target/src/spec/i686_pc_windows_gnu.rs     | 1 +
 compiler/rustc_target/src/spec/i686_pc_windows_gnullvm.rs | 1 +
 compiler/rustc_target/src/spec/i686_pc_windows_msvc.rs    | 1 +
 compiler/rustc_target/src/spec/i686_unknown_freebsd.rs    | 1 +
 compiler/rustc_target/src/spec/i686_unknown_haiku.rs      | 1 +
 compiler/rustc_target/src/spec/i686_unknown_linux_gnu.rs  | 1 +
 compiler/rustc_target/src/spec/i686_unknown_linux_musl.rs | 1 +
 compiler/rustc_target/src/spec/i686_unknown_netbsd.rs     | 1 +
 compiler/rustc_target/src/spec/i686_unknown_openbsd.rs    | 1 +
 compiler/rustc_target/src/spec/i686_uwp_windows_gnu.rs    | 1 +
 compiler/rustc_target/src/spec/i686_uwp_windows_msvc.rs   | 1 +
 compiler/rustc_target/src/spec/i686_wrs_vxworks.rs        | 1 +
 21 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_target/src/spec/i386_apple_ios.rs b/compiler/rustc_target/src/spec/i386_apple_ios.rs
index 5819981612e84..0b51ccf44a5cb 100644
--- a/compiler/rustc_target/src/spec/i386_apple_ios.rs
+++ b/compiler/rustc_target/src/spec/i386_apple_ios.rs
@@ -17,6 +17,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             max_atomic_width: Some(64),
             stack_probes: StackProbeType::X86,
+            features: "+x87".into(),
             ..opts("ios", arch)
         },
     }
diff --git a/compiler/rustc_target/src/spec/i386_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/i386_unknown_linux_gnu.rs
index 801a88933994a..c639bbabf569c 100644
--- a/compiler/rustc_target/src/spec/i386_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/i386_unknown_linux_gnu.rs
@@ -3,6 +3,7 @@ use crate::spec::Target;
 pub fn target() -> Target {
     let mut base = super::i686_unknown_linux_gnu::target();
     base.cpu = "i386".into();
+    base.features = "+x87".into();
     base.llvm_target = "i386-unknown-linux-gnu".into();
     base
 }
diff --git a/compiler/rustc_target/src/spec/i486_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/i486_unknown_linux_gnu.rs
index a11fbecc3c354..27b11e77c389f 100644
--- a/compiler/rustc_target/src/spec/i486_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/i486_unknown_linux_gnu.rs
@@ -3,6 +3,7 @@ use crate::spec::Target;
 pub fn target() -> Target {
     let mut base = super::i686_unknown_linux_gnu::target();
     base.cpu = "i486".into();
+    base.features = "+x87".into();
     base.llvm_target = "i486-unknown-linux-gnu".into();
     base
 }
diff --git a/compiler/rustc_target/src/spec/i586_pc_nto_qnx700.rs b/compiler/rustc_target/src/spec/i586_pc_nto_qnx700.rs
index 68afa7fe40127..d6c204cdd8b9a 100644
--- a/compiler/rustc_target/src/spec/i586_pc_nto_qnx700.rs
+++ b/compiler/rustc_target/src/spec/i586_pc_nto_qnx700.rs
@@ -11,6 +11,7 @@ pub fn target() -> Target {
         arch: "x86".into(),
         options: TargetOptions {
             cpu: "pentium4".into(),
+            features: "+x87".into(),
             max_atomic_width: Some(64),
             pre_link_args: TargetOptions::link_args(
                 LinkerFlavor::Gnu(Cc::Yes, Lld::No),
diff --git a/compiler/rustc_target/src/spec/i586_pc_windows_msvc.rs b/compiler/rustc_target/src/spec/i586_pc_windows_msvc.rs
index befb0f89f3b03..711c0b9c7ec41 100644
--- a/compiler/rustc_target/src/spec/i586_pc_windows_msvc.rs
+++ b/compiler/rustc_target/src/spec/i586_pc_windows_msvc.rs
@@ -3,6 +3,7 @@ use crate::spec::Target;
 pub fn target() -> Target {
     let mut base = super::i686_pc_windows_msvc::target();
     base.cpu = "pentium".into();
+    base.features = "+x87".into();
     base.llvm_target = "i586-pc-windows-msvc".into();
     base
 }
diff --git a/compiler/rustc_target/src/spec/i586_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/i586_unknown_linux_gnu.rs
index b699a7af17749..83ca39aed4caf 100644
--- a/compiler/rustc_target/src/spec/i586_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/i586_unknown_linux_gnu.rs
@@ -3,6 +3,7 @@ use crate::spec::Target;
 pub fn target() -> Target {
     let mut base = super::i686_unknown_linux_gnu::target();
     base.cpu = "pentium".into();
+    base.features = "+x87".into();
     base.llvm_target = "i586-unknown-linux-gnu".into();
     base
 }
diff --git a/compiler/rustc_target/src/spec/i586_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/i586_unknown_linux_musl.rs
index 55a26eb004a7a..f8408debd912c 100644
--- a/compiler/rustc_target/src/spec/i586_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/i586_unknown_linux_musl.rs
@@ -3,6 +3,7 @@ use crate::spec::Target;
 pub fn target() -> Target {
     let mut base = super::i686_unknown_linux_musl::target();
     base.cpu = "pentium".into();
+    base.features = "+x87".into();
     base.llvm_target = "i586-unknown-linux-musl".into();
     base
 }
diff --git a/compiler/rustc_target/src/spec/i686_apple_darwin.rs b/compiler/rustc_target/src/spec/i686_apple_darwin.rs
index b5103d15db695..f8e286c6fe942 100644
--- a/compiler/rustc_target/src/spec/i686_apple_darwin.rs
+++ b/compiler/rustc_target/src/spec/i686_apple_darwin.rs
@@ -5,6 +5,7 @@ pub fn target() -> Target {
     // ld64 only understands i386 and not i686
     let arch = Arch::I386;
     let mut base = opts("macos", arch);
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Darwin(Cc::Yes, Lld::No), &["-m32"]);
     base.stack_probes = StackProbeType::X86;
diff --git a/compiler/rustc_target/src/spec/i686_linux_android.rs b/compiler/rustc_target/src/spec/i686_linux_android.rs
index c7c30c23901d3..422fa006488d6 100644
--- a/compiler/rustc_target/src/spec/i686_linux_android.rs
+++ b/compiler/rustc_target/src/spec/i686_linux_android.rs
@@ -10,7 +10,7 @@ pub fn target() -> Target {
 
     // https://developer.android.com/ndk/guides/abis.html#x86
     base.cpu = "pentiumpro".into();
-    base.features = "+mmx,+sse,+sse2,+sse3,+ssse3".into();
+    base.features = "+x87,+mmx,+sse,+sse2,+sse3,+ssse3".into();
     base.stack_probes = StackProbeType::X86;
 
     Target {
diff --git a/compiler/rustc_target/src/spec/i686_pc_windows_gnu.rs b/compiler/rustc_target/src/spec/i686_pc_windows_gnu.rs
index 7a11138754fa8..e82a05d555064 100644
--- a/compiler/rustc_target/src/spec/i686_pc_windows_gnu.rs
+++ b/compiler/rustc_target/src/spec/i686_pc_windows_gnu.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, Target};
 pub fn target() -> Target {
     let mut base = super::windows_gnu_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.frame_pointer = FramePointer::Always; // Required for backtraces
     base.linker = Some("i686-w64-mingw32-gcc".into());
diff --git a/compiler/rustc_target/src/spec/i686_pc_windows_gnullvm.rs b/compiler/rustc_target/src/spec/i686_pc_windows_gnullvm.rs
index 3154b512a5202..e8bff42dcb903 100644
--- a/compiler/rustc_target/src/spec/i686_pc_windows_gnullvm.rs
+++ b/compiler/rustc_target/src/spec/i686_pc_windows_gnullvm.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, Target};
 pub fn target() -> Target {
     let mut base = super::windows_gnullvm_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.frame_pointer = FramePointer::Always; // Required for backtraces
     base.linker = Some("i686-w64-mingw32-clang".into());
diff --git a/compiler/rustc_target/src/spec/i686_pc_windows_msvc.rs b/compiler/rustc_target/src/spec/i686_pc_windows_msvc.rs
index db4c00dc697d7..f8e4e1f60b0d5 100644
--- a/compiler/rustc_target/src/spec/i686_pc_windows_msvc.rs
+++ b/compiler/rustc_target/src/spec/i686_pc_windows_msvc.rs
@@ -3,6 +3,7 @@ use crate::spec::{LinkerFlavor, Lld, Target};
 pub fn target() -> Target {
     let mut base = super::windows_msvc_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
 
     base.add_pre_link_args(
diff --git a/compiler/rustc_target/src/spec/i686_unknown_freebsd.rs b/compiler/rustc_target/src/spec/i686_unknown_freebsd.rs
index 35ca78034f170..ba8b325787027 100644
--- a/compiler/rustc_target/src/spec/i686_unknown_freebsd.rs
+++ b/compiler/rustc_target/src/spec/i686_unknown_freebsd.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target};
 pub fn target() -> Target {
     let mut base = super::freebsd_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32", "-Wl,-znotext"]);
     base.stack_probes = StackProbeType::X86;
diff --git a/compiler/rustc_target/src/spec/i686_unknown_haiku.rs b/compiler/rustc_target/src/spec/i686_unknown_haiku.rs
index e6b72336c5cf5..08827bfd323be 100644
--- a/compiler/rustc_target/src/spec/i686_unknown_haiku.rs
+++ b/compiler/rustc_target/src/spec/i686_unknown_haiku.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target};
 pub fn target() -> Target {
     let mut base = super::haiku_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
     base.stack_probes = StackProbeType::X86;
diff --git a/compiler/rustc_target/src/spec/i686_unknown_linux_gnu.rs b/compiler/rustc_target/src/spec/i686_unknown_linux_gnu.rs
index 73e536a7e4d93..b2bf7b757dcce 100644
--- a/compiler/rustc_target/src/spec/i686_unknown_linux_gnu.rs
+++ b/compiler/rustc_target/src/spec/i686_unknown_linux_gnu.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, SanitizerSet, StackProbeType, Target};
 pub fn target() -> Target {
     let mut base = super::linux_gnu_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.supported_sanitizers = SanitizerSet::ADDRESS;
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
diff --git a/compiler/rustc_target/src/spec/i686_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/i686_unknown_linux_musl.rs
index 3825082ba25e4..a8a38837bc440 100644
--- a/compiler/rustc_target/src/spec/i686_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/i686_unknown_linux_musl.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, StackProbeType, Target};
 pub fn target() -> Target {
     let mut base = super::linux_musl_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32", "-Wl,-melf_i386"]);
     base.stack_probes = StackProbeType::X86;
diff --git a/compiler/rustc_target/src/spec/i686_unknown_netbsd.rs b/compiler/rustc_target/src/spec/i686_unknown_netbsd.rs
index b191996c7de0d..c6a41a08b7925 100644
--- a/compiler/rustc_target/src/spec/i686_unknown_netbsd.rs
+++ b/compiler/rustc_target/src/spec/i686_unknown_netbsd.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target, TargetOptions};
 pub fn target() -> Target {
     let mut base = super::netbsd_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
     base.stack_probes = StackProbeType::X86;
diff --git a/compiler/rustc_target/src/spec/i686_unknown_openbsd.rs b/compiler/rustc_target/src/spec/i686_unknown_openbsd.rs
index 8babe55971280..f383808798106 100644
--- a/compiler/rustc_target/src/spec/i686_unknown_openbsd.rs
+++ b/compiler/rustc_target/src/spec/i686_unknown_openbsd.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target};
 pub fn target() -> Target {
     let mut base = super::openbsd_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32", "-fuse-ld=lld"]);
     base.stack_probes = StackProbeType::X86;
diff --git a/compiler/rustc_target/src/spec/i686_uwp_windows_gnu.rs b/compiler/rustc_target/src/spec/i686_uwp_windows_gnu.rs
index a3e32569827fb..49ee4d9a5df68 100644
--- a/compiler/rustc_target/src/spec/i686_uwp_windows_gnu.rs
+++ b/compiler/rustc_target/src/spec/i686_uwp_windows_gnu.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, Target};
 pub fn target() -> Target {
     let mut base = super::windows_uwp_gnu_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.frame_pointer = FramePointer::Always; // Required for backtraces
 
diff --git a/compiler/rustc_target/src/spec/i686_uwp_windows_msvc.rs b/compiler/rustc_target/src/spec/i686_uwp_windows_msvc.rs
index 4c657fe908ac4..c84162e4fb521 100644
--- a/compiler/rustc_target/src/spec/i686_uwp_windows_msvc.rs
+++ b/compiler/rustc_target/src/spec/i686_uwp_windows_msvc.rs
@@ -3,6 +3,7 @@ use crate::spec::Target;
 pub fn target() -> Target {
     let mut base = super::windows_uwp_msvc_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
 
     Target {
diff --git a/compiler/rustc_target/src/spec/i686_wrs_vxworks.rs b/compiler/rustc_target/src/spec/i686_wrs_vxworks.rs
index b5cfdfcebea90..0523d59e7f54f 100644
--- a/compiler/rustc_target/src/spec/i686_wrs_vxworks.rs
+++ b/compiler/rustc_target/src/spec/i686_wrs_vxworks.rs
@@ -3,6 +3,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target};
 pub fn target() -> Target {
     let mut base = super::vxworks_base::opts();
     base.cpu = "pentium4".into();
+    base.features = "+x87,+sse,+sse2".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
     base.stack_probes = StackProbeType::X86;