machinst x64: implement float Floor/Ceil/Trunc/Nearest as VM calls;

cranelift/codegen/meta/src/shared/settings.rs

@@ -270,7 +270,7 @@ pub(crate) fn define() -> SettingGroup {
         "enable_heap_access_spectre_mitigation",
         r#"
         Enable Spectre mitigation on heap bounds checks.
-        
+
         This is a no-op for any heap that needs no bounds checks; e.g.,
         if the limit is static and the guard region is large enough that
         the index cannot reach past it.

cranelift/codegen/src/isa/call_conv.rs

@@ -1,5 +1,4 @@
-use crate::isa::TargetIsa;
-use crate::settings::LibcallCallConv;
+use crate::settings::{self, LibcallCallConv};
 use core::fmt;
 use core::str;
 use target_lexicon::{CallingConvention, Triple};
@@ -39,10 +38,10 @@ impl CallConv {
         }
     }
 
-    /// Returns the calling convention used for libcalls for the given ISA.
-    pub fn for_libcall(isa: &dyn TargetIsa) -> Self {
-        match isa.flags().libcall_call_conv() {
-            LibcallCallConv::IsaDefault => isa.default_call_conv(),
+    /// Returns the calling convention used for libcalls according to the current flags.
+    pub fn for_libcall(flags: &settings::Flags, default_call_conv: CallConv) -> Self {
+        match flags.libcall_call_conv() {
+            LibcallCallConv::IsaDefault => default_call_conv,
             LibcallCallConv::Fast => Self::Fast,
             LibcallCallConv::Cold => Self::Cold,
             LibcallCallConv::SystemV => Self::SystemV,

cranelift/codegen/src/isa/x64/abi.rs

@@ -1,8 +1,10 @@
 //! Implementation of the standard x64 ABI.
 
-use alloc::vec::Vec;
 use log::trace;
 use regalloc::{RealReg, Reg, RegClass, Set, SpillSlot, Writable};
+
+use alloc::boxed::Box;
+use alloc::vec::Vec;
 use std::mem;
 
 use crate::binemit::Stackmap;
@@ -1156,13 +1158,29 @@ impl ABICall for X64ABICall {
         }
 
         match &self.dest {
-            &CallDest::ExtName(ref name, ref _reloc_distance) => ctx.emit(Inst::call_known(
+            &CallDest::ExtName(ref name, RelocDistance::Near) => ctx.emit(Inst::call_known(
                 name.clone(),
                 uses,
                 defs,
                 self.loc,
                 self.opcode,
             )),
+            &CallDest::ExtName(ref name, RelocDistance::Far) => {
+                let tmp = ctx.alloc_tmp(RegClass::I64, I64);
+                ctx.emit(Inst::LoadExtName {
+                    dst: tmp,
+                    name: Box::new(name.clone()),
+                    offset: 0,
+                    srcloc: self.loc,
+                });
+                ctx.emit(Inst::call_unknown(
+                    RegMem::reg(tmp.to_reg()),
+                    uses,
+                    defs,
+                    self.loc,
+                    self.opcode,
+                ));
+            }
             &CallDest::Reg(reg) => ctx.emit(Inst::call_unknown(
                 RegMem::reg(reg),
                 uses,

cranelift/codegen/src/isa/x64/lower.rs

@@ -9,7 +9,10 @@ use smallvec::SmallVec;
 use crate::ir::types;
 use crate::ir::types::*;
 use crate::ir::Inst as IRInst;
-use crate::ir::{condcodes::FloatCC, condcodes::IntCC, InstructionData, Opcode, TrapCode, Type};
+use crate::ir::{
+    condcodes::FloatCC, condcodes::IntCC, AbiParam, ArgumentPurpose, ExternalName, InstructionData,
+    LibCall, Opcode, Signature, TrapCode, Type,
+};
 use alloc::boxed::Box;
 use alloc::vec::Vec;
 use cranelift_codegen_shared::condcodes::CondCode;
@@ -23,7 +26,8 @@ use crate::settings::Flags;
 use crate::isa::x64::abi::*;
 use crate::isa::x64::inst::args::*;
 use crate::isa::x64::inst::*;
-use crate::isa::x64::X64Backend;
+use crate::isa::{x64::X64Backend, CallConv};
+use target_lexicon::Triple;
 
 /// Context passed to all lowering functions.
 type Ctx<'a> = &'a mut dyn LowerCtx<I = Inst>;
@@ -222,6 +226,72 @@ fn emit_cmp(ctx: Ctx, insn: IRInst) {
     ctx.emit(Inst::cmp_rmi_r(ty.bytes() as u8, rhs, lhs));
 }
 
+fn make_libcall_sig(ctx: Ctx, insn: IRInst, call_conv: CallConv, ptr_ty: Type) -> Signature {
+    let mut sig = Signature::new(call_conv);
+    for i in 0..ctx.num_inputs(insn) {
+        sig.params.push(AbiParam::new(ctx.input_ty(insn, i)));
+    }
+    for i in 0..ctx.num_outputs(insn) {
+        sig.returns.push(AbiParam::new(ctx.output_ty(insn, i)));
+    }
+    if call_conv.extends_baldrdash() {
+        // Adds the special VMContext parameter to the signature.
+        sig.params
+            .push(AbiParam::special(ptr_ty, ArgumentPurpose::VMContext));
+    }
+    sig
+}
+
+fn emit_vm_call<C: LowerCtx<I = Inst>>(
+    ctx: &mut C,
+    flags: &Flags,
+    triple: &Triple,
+    libcall: LibCall,
+    insn: IRInst,
+    inputs: SmallVec<[InsnInput; 4]>,
+    outputs: SmallVec<[InsnOutput; 2]>,
+) -> CodegenResult<()> {
+    let extname = ExternalName::LibCall(libcall);
+
+    let dist = if flags.use_colocated_libcalls() {
+        RelocDistance::Near
+    } else {
+        RelocDistance::Far
+    };
+
+    // TODO avoid recreating signatures for every single Libcall function.
+    let call_conv = CallConv::for_libcall(flags, CallConv::triple_default(triple));
+    let sig = make_libcall_sig(ctx, insn, call_conv, I64);
+
+    let loc = ctx.srcloc(insn);
+    let mut abi = X64ABICall::from_func(&sig, &extname, dist, loc)?;
+
+    abi.emit_stack_pre_adjust(ctx);
+
+    let vm_context = if call_conv.extends_baldrdash() { 1 } else { 0 };
+    assert!(inputs.len() + vm_context == abi.num_args());
+
+    for (i, input) in inputs.iter().enumerate() {
+        let arg_reg = input_to_reg(ctx, *input);
+        abi.emit_copy_reg_to_arg(ctx, i, arg_reg);
+    }
+    if call_conv.extends_baldrdash() {
+        let vm_context_vreg = ctx
+            .get_vm_context()
+            .expect("should have a VMContext to pass to libcall funcs");
+        abi.emit_copy_reg_to_arg(ctx, inputs.len(), vm_context_vreg);
+    }
+
+    abi.emit_call(ctx);
+    for (i, output) in outputs.iter().enumerate() {
+        let retval_reg = output_to_reg(ctx, *output);
+        abi.emit_copy_retval_to_reg(ctx, i, retval_reg);
+    }
+    abi.emit_stack_post_adjust(ctx);
+
+    Ok(())
+}
+
 //=============================================================================
 // Top-level instruction lowering entry point, for one instruction.
 
@@ -230,6 +300,7 @@ fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
     ctx: &mut C,
     insn: IRInst,
     flags: &Flags,
+    triple: &Triple,
 ) -> CodegenResult<()> {
     let op = ctx.data(insn).opcode();
 
@@ -1203,6 +1274,29 @@ fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
             }
         }
 
+        Opcode::Ceil | Opcode::Floor | Opcode::Nearest | Opcode::Trunc => {
+            // TODO use ROUNDSS/ROUNDSD after sse4.1.
+
+            // Lower to VM calls when there's no access to SSE4.1.
+            let ty = ty.unwrap();
+            let libcall = match (ty, op) {
+                (F32, Opcode::Ceil) => LibCall::CeilF32,
+                (F64, Opcode::Ceil) => LibCall::CeilF64,
+                (F32, Opcode::Floor) => LibCall::FloorF32,
+                (F64, Opcode::Floor) => LibCall::FloorF64,
+                (F32, Opcode::Nearest) => LibCall::NearestF32,
+                (F64, Opcode::Nearest) => LibCall::NearestF64,
+                (F32, Opcode::Trunc) => LibCall::TruncF32,
+                (F64, Opcode::Trunc) => LibCall::TruncF64,
+                _ => panic!(
+                    "unexpected type/opcode {:?}/{:?} in Ceil/Floor/Nearest/Trunc",
+                    ty, op
+                ),
+            };
+
+            emit_vm_call(ctx, flags, triple, libcall, insn, inputs, outputs)?;
+        }
+
         Opcode::Load
         | Opcode::Uload8
         | Opcode::Sload8
@@ -1630,7 +1724,7 @@ impl LowerBackend for X64Backend {
     type MInst = Inst;
 
     fn lower<C: LowerCtx<I = Inst>>(&self, ctx: &mut C, ir_inst: IRInst) -> CodegenResult<()> {
-        lower_insn_to_regs(ctx, ir_inst, &self.flags)
+        lower_insn_to_regs(ctx, ir_inst, &self.flags, &self.triple)
     }
 
     fn lower_branch_group<C: LowerCtx<I = Inst>>(

cranelift/codegen/src/legalizer/libcall.rs

@@ -19,7 +19,7 @@ pub fn expand_as_libcall(inst: ir::Inst, func: &mut ir::Function, isa: &dyn Targ
     let mut args = Vec::new();
     args.extend_from_slice(func.dfg.inst_args(inst));
 
-    let call_conv = CallConv::for_libcall(isa);
+    let call_conv = CallConv::for_libcall(isa.flags(), isa.default_call_conv());
     if call_conv.extends_baldrdash() {
         let vmctx = func
             .special_param(ir::ArgumentPurpose::VMContext)

cranelift/codegen/src/machinst/lower.rs

@@ -8,8 +8,9 @@ use crate::inst_predicates::{has_side_effect_or_load, is_constant_64bit};
 use crate::ir::instructions::BranchInfo;
 use crate::ir::types::I64;
 use crate::ir::{
-    ArgumentExtension, Block, Constant, ConstantData, ExternalName, Function, GlobalValueData,
-    Inst, InstructionData, MemFlags, Opcode, Signature, SourceLoc, Type, Value, ValueDef,
+    ArgumentExtension, ArgumentPurpose, Block, Constant, ConstantData, ExternalName, Function,
+    GlobalValueData, Inst, InstructionData, MemFlags, Opcode, Signature, SourceLoc, Type, Value,
+    ValueDef,
 };
 use crate::machinst::{
     ABIBody, BlockIndex, BlockLoweringOrder, LoweredBlock, MachLabel, VCode, VCodeBuilder,
@@ -67,6 +68,8 @@ pub trait LowerCtx {
     /// not allow the backend to specify its own result register for the return?
     /// Because there may be multiple return points.)
     fn retval(&self, idx: usize) -> Writable<Reg>;
+    /// Returns the vreg containing the VmContext parameter, if there's one.
+    fn get_vm_context(&self) -> Option<Reg>;
 
     // General instruction queries:
 
@@ -261,6 +264,10 @@ pub struct Lower<'func, I: VCodeInst> {
 
     /// The register to use for GetPinnedReg, if any, on this architecture.
     pinned_reg: Option<Reg>,
+
+    /// The vreg containing the special VmContext parameter, if it is present in the current
+    /// function's signature.
+    vm_context: Option<Reg>,
 }
 
 /// Notion of "relocation distance". This gives an estimate of how far away a symbol will be from a
@@ -331,6 +338,15 @@ impl<'func, I: VCodeInst> Lower<'func, I> {
             }
         }
 
+        let vm_context = f
+            .signature
+            .special_param_index(ArgumentPurpose::VMContext)
+            .map(|vm_context_index| {
+                let entry_block = f.layout.entry_block().unwrap();
+                let param = f.dfg.block_params(entry_block)[vm_context_index];
+                value_regs[param]
+            });
+
         // Assign a vreg to each return value.
         let mut retval_regs = vec![];
         for ret in &f.signature.returns {
@@ -387,6 +403,7 @@ impl<'func, I: VCodeInst> Lower<'func, I> {
             bb_insts: vec![],
             ir_insts: vec![],
             pinned_reg: None,
+            vm_context,
         })
     }
 
@@ -830,6 +847,10 @@ impl<'func, I: VCodeInst> LowerCtx for Lower<'func, I> {
         Writable::from_reg(self.retval_regs[idx].0)
     }
 
+    fn get_vm_context(&self) -> Option<Reg> {
+        self.vm_context
+    }
+
     fn data(&self, ir_inst: Inst) -> &InstructionData {
         &self.f.dfg[ir_inst]
     }