Implement some llvm.x86.sse2.* intrinsics and add tests

Implements LLVM intrisics needed to run most SSE2 functions from `core::arch::x86{,_64}`.

Also adds miri tests for those functions (mostly copied from core_arch tests).

Author: eduardosm

src/shims/foreign_items.rs

@@ -1037,6 +1037,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     this, link_name, abi, args, dest,
                 );
             }
+            name if name.starts_with("llvm.x86.sse2.") => {
+                return shims::x86::sse2::EvalContextExt::emulate_x86_sse2_intrinsic(
+                    this, link_name, abi, args, dest,
+                );
+            }
 
             // Platform-specific shims
             _ =>

src/shims/x86/mod.rs

@@ -1 +1,45 @@
+use crate::InterpResult;
+
 pub(super) mod sse;
+pub(super) mod sse2;
+
+/// Floating point comparison operation
+///
+/// <https://www.felixcloutier.com/x86/cmpss>
+/// <https://www.felixcloutier.com/x86/cmpps>
+/// <https://www.felixcloutier.com/x86/cmpsd>
+/// <https://www.felixcloutier.com/x86/cmppd>
+#[derive(Copy, Clone)]
+enum FloatCmpOp {
+    Eq,
+    Lt,
+    Le,
+    Unord,
+    Neq,
+    /// Not less-than
+    Nlt,
+    /// Not less-or-equal
+    Nle,
+    /// Ordered, i.e. neither of them is NaN
+    Ord,
+}
+
+impl FloatCmpOp {
+    /// Convert from the `imm` argument used to specify the comparison
+    /// operation in intrinsics such as `llvm.x86.sse.cmp.ss`.
+    fn from_intrinsic_imm(imm: i8, intrinsic: &str) -> InterpResult<'_, Self> {
+        match imm {
+            0 => Ok(Self::Eq),
+            1 => Ok(Self::Lt),
+            2 => Ok(Self::Le),
+            3 => Ok(Self::Unord),
+            4 => Ok(Self::Neq),
+            5 => Ok(Self::Nlt),
+            6 => Ok(Self::Nle),
+            7 => Ok(Self::Ord),
+            imm => {
+                throw_unsup_format!("invalid `imm` parameter of {intrinsic}: {imm}");
+            }
+        }
+    }
+}

src/shims/x86/sse.rs

@@ -5,6 +5,7 @@ use rustc_target::spec::abi::Abi;
 
 use rand::Rng as _;
 
+use super::FloatCmpOp;
 use crate::*;
 use shims::foreign_items::EmulateByNameResult;
 
@@ -100,22 +101,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 let [left, right, imm] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 
-                let which = match this.read_scalar(imm)?.to_i8()? {
-                    0 => FloatBinOp::Cmp(FloatCmpOp::Eq),
-                    1 => FloatBinOp::Cmp(FloatCmpOp::Lt),
-                    2 => FloatBinOp::Cmp(FloatCmpOp::Le),
-                    3 => FloatBinOp::Cmp(FloatCmpOp::Unord),
-                    4 => FloatBinOp::Cmp(FloatCmpOp::Neq),
-                    5 => FloatBinOp::Cmp(FloatCmpOp::Nlt),
-                    6 => FloatBinOp::Cmp(FloatCmpOp::Nle),
-                    7 => FloatBinOp::Cmp(FloatCmpOp::Ord),
-                    imm => {
-                        throw_unsup_format!(
-                            "invalid 3rd parameter of llvm.x86.sse.cmp.ps: {}",
-                            imm
-                        );
-                    }
-                };
+                let which = FloatBinOp::Cmp(FloatCmpOp::from_intrinsic_imm(
+                    this.read_scalar(imm)?.to_i8()?,
+                    "llvm.x86.sse.cmp.ss",
+                )?);
 
                 bin_op_ss(this, which, left, right, dest)?;
             }
@@ -127,22 +116,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 let [left, right, imm] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 
-                let which = match this.read_scalar(imm)?.to_i8()? {
-                    0 => FloatBinOp::Cmp(FloatCmpOp::Eq),
-                    1 => FloatBinOp::Cmp(FloatCmpOp::Lt),
-                    2 => FloatBinOp::Cmp(FloatCmpOp::Le),
-                    3 => FloatBinOp::Cmp(FloatCmpOp::Unord),
-                    4 => FloatBinOp::Cmp(FloatCmpOp::Neq),
-                    5 => FloatBinOp::Cmp(FloatCmpOp::Nlt),
-                    6 => FloatBinOp::Cmp(FloatCmpOp::Nle),
-                    7 => FloatBinOp::Cmp(FloatCmpOp::Ord),
-                    imm => {
-                        throw_unsup_format!(
-                            "invalid 3rd parameter of llvm.x86.sse.cmp.ps: {}",
-                            imm
-                        );
-                    }
-                };
+                let which = FloatBinOp::Cmp(FloatCmpOp::from_intrinsic_imm(
+                    this.read_scalar(imm)?.to_i8()?,
+                    "llvm.x86.sse.cmp.ps",
+                )?);
 
                 bin_op_ps(this, which, left, right, dest)?;
             }
@@ -292,6 +269,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     let op = this.read_scalar(&this.project_index(&op, i)?)?;
                     let op = op.to_u32()?;
 
+                    // Extract the highest bit of `op` and place it in the `i`-th bit of `res`
                     res |= (op >> 31) << i;
                 }
 
@@ -303,25 +281,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
     }
 }
 
-/// Floating point comparison operation
-///
-/// <https://www.felixcloutier.com/x86/cmpss>
-/// <https://www.felixcloutier.com/x86/cmpps>
-#[derive(Copy, Clone)]
-enum FloatCmpOp {
-    Eq,
-    Lt,
-    Le,
-    Unord,
-    Neq,
-    /// Not less-than
-    Nlt,
-    /// Not less-or-equal
-    Nle,
-    /// Ordered, i.e. neither of them is NaN
-    Ord,
-}
-
 #[derive(Copy, Clone)]
 enum FloatBinOp {
     /// Arithmetic operation