Rollup merge of #92425 - calebzulawski:simd-cast, r=workingjubilee

Improve SIMD casts

* Allows `simd_cast` intrinsic to take `usize` and `isize`
* Adds `simd_as` intrinsic, which is the same as `simd_cast` except for saturating float-to-int conversions (matching the behavior of `as`).

cc `@workingjubilee`

2 files changed, 62 insertions, 27 deletions

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 5217fa2758f..8a9450c20dd 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -731,27 +731,11 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn fptoui_sat(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> Option<&'ll Value> {
-        if !self.fptoint_sat_broken_in_llvm() {
-            let src_ty = self.cx.val_ty(val);
-            let float_width = self.cx.float_width(src_ty);
-            let int_width = self.cx.int_width(dest_ty);
-            let name = format!("llvm.fptoui.sat.i{}.f{}", int_width, float_width);
-            return Some(self.call_intrinsic(&name, &[val]));
-        }
-
-        None
+        self.fptoint_sat(false, val, dest_ty)
     }
 
     fn fptosi_sat(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> Option<&'ll Value> {
-        if !self.fptoint_sat_broken_in_llvm() {
-            let src_ty = self.cx.val_ty(val);
-            let float_width = self.cx.float_width(src_ty);
-            let int_width = self.cx.int_width(dest_ty);
-            let name = format!("llvm.fptosi.sat.i{}.f{}", int_width, float_width);
-            return Some(self.call_intrinsic(&name, &[val]));
-        }
-
-        None
+        self.fptoint_sat(true, val, dest_ty)
     }
 
     fn fptoui(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> &'ll Value {
@@ -1455,4 +1439,43 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
             _ => false,
         }
     }
+
+    fn fptoint_sat(
+        &mut self,
+        signed: bool,
+        val: &'ll Value,
+        dest_ty: &'ll Type,
+    ) -> Option<&'ll Value> {
+        if !self.fptoint_sat_broken_in_llvm() {
+            let src_ty = self.cx.val_ty(val);
+            let (float_ty, int_ty, vector_length) = if self.cx.type_kind(src_ty) == TypeKind::Vector
+            {
+                assert_eq!(self.cx.vector_length(src_ty), self.cx.vector_length(dest_ty));
+                (
+                    self.cx.element_type(src_ty),
+                    self.cx.element_type(dest_ty),
+                    Some(self.cx.vector_length(src_ty)),
+                )
+            } else {
+                (src_ty, dest_ty, None)
+            };
+            let float_width = self.cx.float_width(float_ty);
+            let int_width = self.cx.int_width(int_ty);
+
+            let instr = if signed { "fptosi" } else { "fptoui" };
+            let name = if let Some(vector_length) = vector_length {
+                format!(
+                    "llvm.{}.sat.v{}i{}.v{}f{}",
+                    instr, vector_length, int_width, vector_length, float_width
+                )
+            } else {
+                format!("llvm.{}.sat.i{}.f{}", instr, int_width, float_width)
+            };
+            let f =
+                self.declare_cfn(&name, llvm::UnnamedAddr::No, self.type_func(&[src_ty], dest_ty));
+            Some(self.call(self.type_func(&[src_ty], dest_ty), f, &[val], None))
+        } else {
+            None
+        }
+    }
 }
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index cebb6d13c4e..5adfa18035a 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -1688,7 +1688,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
     bitwise_red!(simd_reduce_all: vector_reduce_and, true);
     bitwise_red!(simd_reduce_any: vector_reduce_or, true);
 
-    if name == sym::simd_cast {
+    if name == sym::simd_cast || name == sym::simd_as {
         require_simd!(ret_ty, "return");
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
         require!(
@@ -1714,14 +1714,26 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         let (in_style, in_width) = match in_elem.kind() {
             // vectors of pointer-sized integers should've been
             // disallowed before here, so this unwrap is safe.
-            ty::Int(i) => (Style::Int(true), i.bit_width().unwrap()),
-            ty::Uint(u) => (Style::Int(false), u.bit_width().unwrap()),
+            ty::Int(i) => (
+                Style::Int(true),
+                i.normalize(bx.tcx().sess.target.pointer_width).bit_width().unwrap(),
+            ),
+            ty::Uint(u) => (
+                Style::Int(false),
+                u.normalize(bx.tcx().sess.target.pointer_width).bit_width().unwrap(),
+            ),
             ty::Float(f) => (Style::Float, f.bit_width()),
             _ => (Style::Unsupported, 0),
         };
         let (out_style, out_width) = match out_elem.kind() {
-            ty::Int(i) => (Style::Int(true), i.bit_width().unwrap()),
-            ty::Uint(u) => (Style::Int(false), u.bit_width().unwrap()),
+            ty::Int(i) => (
+                Style::Int(true),
+                i.normalize(bx.tcx().sess.target.pointer_width).bit_width().unwrap(),
+            ),
+            ty::Uint(u) => (
+                Style::Int(false),
+                u.normalize(bx.tcx().sess.target.pointer_width).bit_width().unwrap(),
+            ),
             ty::Float(f) => (Style::Float, f.bit_width()),
             _ => (Style::Unsupported, 0),
         };
@@ -1748,10 +1760,10 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                 });
             }
             (Style::Float, Style::Int(out_is_signed)) => {
-                return Ok(if out_is_signed {
-                    bx.fptosi(args[0].immediate(), llret_ty)
-                } else {
-                    bx.fptoui(args[0].immediate(), llret_ty)
+                return Ok(match (out_is_signed, name == sym::simd_as) {
+                    (false, false) => bx.fptoui(args[0].immediate(), llret_ty),
+                    (true, false) => bx.fptosi(args[0].immediate(), llret_ty),
+                    (_, true) => bx.cast_float_to_int(out_is_signed, args[0].immediate(), llret_ty),
                 });
             }
             (Style::Float, Style::Float) => {