diff --git a/library/compiler-builtins/.github/workflows/main.yaml b/library/compiler-builtins/.github/workflows/main.yaml
index c54df2e90b793..3afadbfe89418 100644
--- a/library/compiler-builtins/.github/workflows/main.yaml
+++ b/library/compiler-builtins/.github/workflows/main.yaml
@@ -51,8 +51,7 @@ jobs:
         - target: aarch64-unknown-linux-gnu
           os: ubuntu-24.04-arm
         - target: aarch64-pc-windows-msvc
-          os: windows-2025
-          build_only: 1
+          os: windows-11-arm
         - target: arm-unknown-linux-gnueabi
           os: ubuntu-24.04
         - target: arm-unknown-linux-gnueabihf
diff --git a/library/compiler-builtins/builtins-test/benches/float_conv.rs b/library/compiler-builtins/builtins-test/benches/float_conv.rs
index e0f488eb6855d..40c13d270ac8e 100644
--- a/library/compiler-builtins/builtins-test/benches/float_conv.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_conv.rs
@@ -1,4 +1,3 @@
-#![allow(improper_ctypes)]
 #![cfg_attr(f128_enabled, feature(f128))]
 
 use builtins_test::float_bench;
diff --git a/library/compiler-builtins/builtins-test/tests/addsub.rs b/library/compiler-builtins/builtins-test/tests/addsub.rs
index abe7dde645e04..f3334bd0e2d3a 100644
--- a/library/compiler-builtins/builtins-test/tests/addsub.rs
+++ b/library/compiler-builtins/builtins-test/tests/addsub.rs
@@ -1,4 +1,5 @@
 #![allow(unused_macros)]
+#![cfg_attr(f16_enabled, feature(f16))]
 #![cfg_attr(f128_enabled, feature(f128))]
 
 use builtins_test::*;
@@ -115,28 +116,25 @@ macro_rules! float_sum {
 mod float_addsub {
     use super::*;
 
+    #[cfg(f16_enabled)]
+    float_sum! {
+        f16, __addhf3, __subhf3, Half, all();
+    }
+
     float_sum! {
         f32, __addsf3, __subsf3, Single, all();
         f64, __adddf3, __subdf3, Double, all();
     }
-}
-
-#[cfg(f128_enabled)]
-#[cfg(not(x86_no_sse))]
-#[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
-mod float_addsub_f128 {
-    use super::*;
 
+    #[cfg(f128_enabled)]
+    #[cfg(not(x86_no_sse))]
+    #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
     float_sum! {
         f128, __addtf3, __subtf3, Quad, not(feature = "no-sys-f128");
     }
-}
-
-#[cfg(f128_enabled)]
-#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
-mod float_addsub_f128_ppc {
-    use super::*;
 
+    #[cfg(f128_enabled)]
+    #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
     float_sum! {
         f128, __addkf3, __subkf3, Quad, not(feature = "no-sys-f128");
     }
diff --git a/library/compiler-builtins/builtins-test/tests/cmp.rs b/library/compiler-builtins/builtins-test/tests/cmp.rs
index a904dc5f7de4d..4b01b6ca1c7d7 100644
--- a/library/compiler-builtins/builtins-test/tests/cmp.rs
+++ b/library/compiler-builtins/builtins-test/tests/cmp.rs
@@ -1,5 +1,6 @@
 #![allow(unused_macros)]
 #![allow(unreachable_code)]
+#![cfg_attr(f16_enabled, feature(f16))]
 #![cfg_attr(f128_enabled, feature(f128))]
 
 use builtins_test::*;
@@ -51,6 +52,26 @@ mod float_comparisons {
         };
     }
 
+    #[test]
+    #[cfg(f16_enabled)]
+    fn cmp_f16() {
+        use compiler_builtins::float::cmp::{
+            __eqhf2, __gehf2, __gthf2, __lehf2, __lthf2, __nehf2, __unordhf2,
+        };
+
+        fuzz_float_2(N, |x: f16, y: f16| {
+            assert_eq!(__unordhf2(x, y) != 0, x.is_nan() || y.is_nan());
+            cmp!(f16, x, y, Half, all(),
+                1, __lthf2;
+                1, __lehf2;
+                1, __eqhf2;
+                -1, __gehf2;
+                -1, __gthf2;
+                1, __nehf2;
+            );
+        });
+    }
+
     #[test]
     fn cmp_f32() {
         use compiler_builtins::float::cmp::{
diff --git a/library/compiler-builtins/builtins-test/tests/mul.rs b/library/compiler-builtins/builtins-test/tests/mul.rs
index 3072b45dca03f..bbf1157db42f9 100644
--- a/library/compiler-builtins/builtins-test/tests/mul.rs
+++ b/library/compiler-builtins/builtins-test/tests/mul.rs
@@ -1,5 +1,6 @@
-#![allow(unused_macros)]
+#![cfg_attr(f16_enabled, feature(f16))]
 #![cfg_attr(f128_enabled, feature(f128))]
+#![allow(unused_macros)]
 
 use builtins_test::*;
 
@@ -117,6 +118,11 @@ macro_rules! float_mul {
 mod float_mul {
     use super::*;
 
+    #[cfg(f16_enabled)]
+    float_mul! {
+        f16, __mulhf3, Half, all();
+    }
+
     // FIXME(#616): Stop ignoring arches that don't have native support once fix for builtins is in
     // nightly.
     float_mul! {
diff --git a/library/compiler-builtins/compiler-builtins/src/float/add.rs b/library/compiler-builtins/compiler-builtins/src/float/add.rs
index 0cc362f705b11..acdcd2ebe3133 100644
--- a/library/compiler-builtins/compiler-builtins/src/float/add.rs
+++ b/library/compiler-builtins/compiler-builtins/src/float/add.rs
@@ -130,7 +130,7 @@ where
             return F::from_bits(MinInt::ZERO);
         }
 
-        // If partial cancellation occured, we need to left-shift the result
+        // If partial cancellation occurred, we need to left-shift the result
         // and adjust the exponent:
         if a_significand < implicit_bit << 3 {
             let shift = a_significand.leading_zeros() as i32
@@ -191,6 +191,11 @@ where
 }
 
 intrinsics! {
+    #[cfg(f16_enabled)]
+    pub extern "C" fn __addhf3(a: f16, b: f16) -> f16 {
+        add(a, b)
+    }
+
     #[aapcs_on_arm]
     #[arm_aeabi_alias = __aeabi_fadd]
     pub extern "C" fn __addsf3(a: f32, b: f32) -> f32 {
diff --git a/library/compiler-builtins/compiler-builtins/src/float/cmp.rs b/library/compiler-builtins/compiler-builtins/src/float/cmp.rs
index f1e54dc1c83d1..8ab39c2b5914d 100644
--- a/library/compiler-builtins/compiler-builtins/src/float/cmp.rs
+++ b/library/compiler-builtins/compiler-builtins/src/float/cmp.rs
@@ -115,6 +115,37 @@ fn unord<F: Float>(a: F, b: F) -> bool {
     a_abs > inf_rep || b_abs > inf_rep
 }
 
+#[cfg(f16_enabled)]
+intrinsics! {
+    pub extern "C" fn __lehf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        cmp(a, b).to_le_abi()
+    }
+
+    pub extern "C" fn __gehf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        cmp(a, b).to_ge_abi()
+    }
+
+    pub extern "C" fn __unordhf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        unord(a, b) as crate::float::cmp::CmpResult
+    }
+
+    pub extern "C" fn __eqhf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        cmp(a, b).to_le_abi()
+    }
+
+    pub extern "C" fn __lthf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        cmp(a, b).to_le_abi()
+    }
+
+    pub extern "C" fn __nehf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        cmp(a, b).to_le_abi()
+    }
+
+    pub extern "C" fn __gthf2(a: f16, b: f16) -> crate::float::cmp::CmpResult {
+        cmp(a, b).to_ge_abi()
+    }
+}
+
 intrinsics! {
     pub extern "C" fn __lesf2(a: f32, b: f32) -> crate::float::cmp::CmpResult {
         cmp(a, b).to_le_abi()
diff --git a/library/compiler-builtins/compiler-builtins/src/float/mul.rs b/library/compiler-builtins/compiler-builtins/src/float/mul.rs
index dbed3095cda5d..49a2414eb5c69 100644
--- a/library/compiler-builtins/compiler-builtins/src/float/mul.rs
+++ b/library/compiler-builtins/compiler-builtins/src/float/mul.rs
@@ -180,6 +180,11 @@ where
 }
 
 intrinsics! {
+    #[cfg(f16_enabled)]
+    pub extern "C" fn __mulhf3(a: f16, b: f16) -> f16 {
+        mul(a, b)
+    }
+
     #[aapcs_on_arm]
     #[arm_aeabi_alias = __aeabi_fmul]
     pub extern "C" fn __mulsf3(a: f32, b: f32) -> f32 {
diff --git a/library/compiler-builtins/compiler-builtins/src/float/sub.rs b/library/compiler-builtins/compiler-builtins/src/float/sub.rs
index a0fd9dff97fcf..48ef33b0b826f 100644
--- a/library/compiler-builtins/compiler-builtins/src/float/sub.rs
+++ b/library/compiler-builtins/compiler-builtins/src/float/sub.rs
@@ -1,6 +1,11 @@
 use crate::float::Float;
 
 intrinsics! {
+    #[cfg(f16_enabled)]
+    pub extern "C" fn __subhf3(a: f16, b: f16) -> f16 {
+        crate::float::add::__addhf3(a, f16::from_bits(b.to_bits() ^ f16::SIGN_MASK))
+    }
+
     #[arm_aeabi_alias = __aeabi_fsub]
     pub extern "C" fn __subsf3(a: f32, b: f32) -> f32 {
         crate::float::add::__addsf3(a, f32::from_bits(b.to_bits() ^ f32::SIGN_MASK))
diff --git a/library/compiler-builtins/compiler-builtins/src/lib.rs b/library/compiler-builtins/compiler-builtins/src/lib.rs
index ca75f44e02a9c..b111dc0bd18f3 100644
--- a/library/compiler-builtins/compiler-builtins/src/lib.rs
+++ b/library/compiler-builtins/compiler-builtins/src/lib.rs
@@ -18,10 +18,6 @@
 #![no_std]
 #![allow(unused_features)]
 #![allow(internal_features)]
-// We use `u128` in a whole bunch of places which we currently agree with the
-// compiler on ABIs and such, so we should be "good enough" for now and changes
-// to the `u128` ABI will be reflected here.
-#![allow(improper_ctypes, improper_ctypes_definitions)]
 // `mem::swap` cannot be used because it may generate references to memcpy in unoptimized code.
 #![allow(clippy::manual_swap)]
 // Support compiling on both stage0 and stage1 which may differ in supported stable features.
diff --git a/library/compiler-builtins/compiler-builtins/src/probestack.rs b/library/compiler-builtins/compiler-builtins/src/probestack.rs
index 9a18216da99a3..72975485a7765 100644
--- a/library/compiler-builtins/compiler-builtins/src/probestack.rs
+++ b/library/compiler-builtins/compiler-builtins/src/probestack.rs
@@ -73,7 +73,7 @@ pub unsafe extern "custom" fn __rust_probestack() {
             // page needed.
             //
             // Note that we're also testing against `8(%rsp)` to account for the 8
-            // bytes pushed on the stack orginally with our return address. Using
+            // bytes pushed on the stack originally with our return address. Using
             // `8(%rsp)` simulates us testing the stack pointer in the caller's
             // context.
 
diff --git a/library/compiler-builtins/crates/symbol-check/src/main.rs b/library/compiler-builtins/crates/symbol-check/src/main.rs
index 1312a71797032..4e94552331a0f 100644
--- a/library/compiler-builtins/crates/symbol-check/src/main.rs
+++ b/library/compiler-builtins/crates/symbol-check/src/main.rs
@@ -9,7 +9,7 @@ use std::process::{Command, Stdio};
 
 use object::read::archive::{ArchiveFile, ArchiveMember};
 use object::{
-    File as ObjFile, Object, ObjectSymbol, Symbol, SymbolKind, SymbolScope, SymbolSection,
+    File as ObjFile, Object, ObjectSection, ObjectSymbol, Symbol, SymbolKind, SymbolScope,
 };
 use serde_json::Value;
 
@@ -154,7 +154,7 @@ struct SymInfo {
     name: String,
     kind: SymbolKind,
     scope: SymbolScope,
-    section: SymbolSection,
+    section: String,
     is_undefined: bool,
     is_global: bool,
     is_local: bool,
@@ -165,12 +165,22 @@ struct SymInfo {
 }
 
 impl SymInfo {
-    fn new(sym: &Symbol, member: &ArchiveMember) -> Self {
+    fn new(sym: &Symbol, obj: &ObjFile, member: &ArchiveMember) -> Self {
+        // Include the section name if possible. Fall back to the `Section` debug impl if not.
+        let section = sym.section();
+        let section_name = sym
+            .section()
+            .index()
+            .and_then(|idx| obj.section_by_index(idx).ok())
+            .and_then(|sec| sec.name().ok())
+            .map(ToString::to_string)
+            .unwrap_or_else(|| format!("{section:?}"));
+
         Self {
             name: sym.name().expect("missing name").to_owned(),
             kind: sym.kind(),
             scope: sym.scope(),
-            section: sym.section(),
+            section: section_name,
             is_undefined: sym.is_undefined(),
             is_global: sym.is_global(),
             is_local: sym.is_local(),
@@ -192,22 +202,27 @@ fn verify_no_duplicates(archive: &Archive) {
     let mut dups = Vec::new();
     let mut found_any = false;
 
-    archive.for_each_symbol(|symbol, member| {
+    archive.for_each_symbol(|symbol, obj, member| {
         // Only check defined globals
         if !symbol.is_global() || symbol.is_undefined() {
             return;
         }
 
-        let sym = SymInfo::new(&symbol, member);
+        let sym = SymInfo::new(&symbol, obj, member);
 
         // x86-32 includes multiple copies of thunk symbols
         if sym.name.starts_with("__x86.get_pc_thunk") {
             return;
         }
 
+        // GDB pretty printing symbols may show up more than once but are weak.
+        if sym.section == ".debug_gdb_scripts" && sym.is_weak {
+            return;
+        }
+
         // Windows has symbols for literal numeric constants, string literals, and MinGW pseudo-
         // relocations. These are allowed to have repeated definitions.
-        let win_allowed_dup_pfx = ["__real@", "__xmm@", "??_C@_", ".refptr"];
+        let win_allowed_dup_pfx = ["__real@", "__xmm@", "__ymm@", "??_C@_", ".refptr"];
         if win_allowed_dup_pfx
             .iter()
             .any(|pfx| sym.name.starts_with(pfx))
@@ -244,7 +259,7 @@ fn verify_core_symbols(archive: &Archive) {
     let mut undefined = Vec::new();
     let mut has_symbols = false;
 
-    archive.for_each_symbol(|symbol, member| {
+    archive.for_each_symbol(|symbol, obj, member| {
         has_symbols = true;
 
         // Find only symbols from `core`
@@ -252,7 +267,7 @@ fn verify_core_symbols(archive: &Archive) {
             return;
         }
 
-        let sym = SymInfo::new(&symbol, member);
+        let sym = SymInfo::new(&symbol, obj, member);
         if sym.is_undefined {
             undefined.push(sym);
         } else {
@@ -304,9 +319,9 @@ impl Archive {
     }
 
     /// For a given archive, do something with each symbol.
-    fn for_each_symbol(&self, mut f: impl FnMut(Symbol, &ArchiveMember)) {
+    fn for_each_symbol(&self, mut f: impl FnMut(Symbol, &ObjFile, &ArchiveMember)) {
         self.for_each_object(|obj, member| {
-            obj.symbols().for_each(|sym| f(sym, member));
+            obj.symbols().for_each(|sym| f(sym, &obj, member));
         });
     }
 }
diff --git a/library/compiler-builtins/etc/update-api-list.py b/library/compiler-builtins/etc/update-api-list.py
index 28ff22f4cbb3b..76c75cbf4dccb 100755
--- a/library/compiler-builtins/etc/update-api-list.py
+++ b/library/compiler-builtins/etc/update-api-list.py
@@ -34,7 +34,7 @@ def eprint(*args, **kwargs):
 
 @dataclass
 class Crate:
-    """Representation of public interfaces and function defintion locations in
+    """Representation of public interfaces and function definition locations in
     `libm`.
     """
 
diff --git a/library/compiler-builtins/libm/src/math/rem_pio2_large.rs b/library/compiler-builtins/libm/src/math/rem_pio2_large.rs
index f1fdf3673a8dc..bb2c532916b2a 100644
--- a/library/compiler-builtins/libm/src/math/rem_pio2_large.rs
+++ b/library/compiler-builtins/libm/src/math/rem_pio2_large.rs
@@ -146,7 +146,7 @@ const PIO2: [f64; 8] = [
 //                      x[i] = floor(z)
 //                      z    = (z-x[i])*2**24
 //
-//      y[]     ouput result in an array of double precision numbers.
+//      y[]     output result in an array of double precision numbers.
 //              The dimension of y[] is:
 //                      24-bit  precision       1
 //                      53-bit  precision       2
diff --git a/library/compiler-builtins/rust-version b/library/compiler-builtins/rust-version
index a4db05a879683..8489eacfcda28 100644
--- a/library/compiler-builtins/rust-version
+++ b/library/compiler-builtins/rust-version
@@ -1 +1 @@
-82310651b93a594a3fd69015e1562186a080d94c
+d36f964125163c2e698de5559efefb8217b8b7f0