AArch64: port tls_value to ISLE. (#4821)

cranelift/codegen/src/isa/aarch64/inst.isle

@@ -825,7 +825,8 @@
 
        ;; A call to the `ElfTlsGetAddr` libcall. Returns address of TLS symbol in x0.
        (ElfTlsGetAddr
-        (symbol ExternalName))
+        (symbol ExternalName)
+        (rd WritableReg))
 
        ;; An unwind pseudo-instruction.
        (Unwind
@@ -3068,3 +3069,12 @@
       (if (ty_vec64 ty))
       (let ((src Reg (mov_from_vec src 0 (ScalarSize.Size64))))
        (cmp_imm (OperandSize.Size64) src (u8_into_imm12 0))))
+
+;;;; TLS Values ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; Helper for emitting ElfTlsGetAddr.
+(decl elf_tls_get_addr (ExternalName) Reg)
+(rule (elf_tls_get_addr name)
+      (let ((dst WritableReg (temp_writable_reg $I64))
+            (_ Unit (emit (MInst.ElfTlsGetAddr name dst))))
+        dst))

cranelift/codegen/src/isa/aarch64/inst/emit.rs

@@ -3191,7 +3191,10 @@ impl MachInstEmit for Inst {
                 }
             }
 
-            &Inst::ElfTlsGetAddr { ref symbol } => {
+            &Inst::ElfTlsGetAddr { ref symbol, rd } => {
+                let rd = allocs.next_writable(rd);
+                assert_eq!(xreg(0), rd.to_reg());
+
                 // This is the instruction sequence that GCC emits for ELF GD TLS Relocations in aarch64
                 // See: https://gcc.godbolt.org/z/KhMh5Gvra
 

cranelift/codegen/src/isa/aarch64/inst/mod.rs

@@ -1044,8 +1044,8 @@ fn aarch64_get_operands<F: Fn(VReg) -> VReg>(inst: &Inst, collector: &mut Operan
         }
         &Inst::VirtualSPOffsetAdj { .. } => {}
 
-        &Inst::ElfTlsGetAddr { .. } => {
-            collector.reg_def(Writable::from_reg(regs::xreg(0)));
+        &Inst::ElfTlsGetAddr { rd, .. } => {
+            collector.reg_fixed_def(rd, regs::xreg(0));
             let mut clobbers = AArch64MachineDeps::get_regs_clobbered_by_call(CallConv::SystemV);
             clobbers.remove(regs::xreg_preg(0));
             collector.reg_clobbers(clobbers);
@@ -2710,8 +2710,9 @@ impl Inst {
             }
             &Inst::EmitIsland { needed_space } => format!("emit_island {}", needed_space),
 
-            &Inst::ElfTlsGetAddr { ref symbol } => {
-                format!("x0 = elf_tls_get_addr {}", symbol.display(None))
+            &Inst::ElfTlsGetAddr { ref symbol, rd } => {
+                let rd = pretty_print_reg(rd.to_reg(), allocs);
+                format!("elf_tls_get_addr {}, {}", rd, symbol.display(None))
             }
             &Inst::Unwind { ref inst } => {
                 format!("unwind {:?}", inst)

cranelift/codegen/src/isa/aarch64/lower.isle

@@ -2364,7 +2364,9 @@
 
 ;;; Rules for `tls_value` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-;; TODO.
+(rule (lower (tls_value (symbol_value_data name _ _)))
+      (if (tls_model_is_elf_gd))
+      (elf_tls_get_addr name))
 
 ;;; Rules for `fcvt_low_from_sint` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 

cranelift/codegen/src/isa/aarch64/lower_inst.rs

@@ -9,7 +9,7 @@ use crate::isa::aarch64::inst::*;
 use crate::isa::aarch64::settings as aarch64_settings;
 use crate::machinst::lower::*;
 use crate::machinst::*;
-use crate::settings::{Flags, TlsModel};
+use crate::settings::Flags;
 use crate::{CodegenError, CodegenResult};
 use alloc::boxed::Box;
 use alloc::vec::Vec;
@@ -459,23 +459,7 @@ pub(crate) fn lower_insn_to_regs(
             implemented_in_isle(ctx)
         }
 
-        Opcode::TlsValue => match flags.tls_model() {
-            TlsModel::ElfGd => {
-                let dst = get_output_reg(ctx, outputs[0]).only_reg().unwrap();
-                let (name, _, _) = ctx.symbol_value(insn).unwrap();
-                let symbol = name.clone();
-                ctx.emit(Inst::ElfTlsGetAddr { symbol });
-
-                let x0 = xreg(0);
-                ctx.emit(Inst::gen_move(dst, x0, I64));
-            }
-            _ => {
-                return Err(CodegenError::Unsupported(format!(
-                    "Unimplemented TLS model in AArch64 backend: {:?}",
-                    flags.tls_model()
-                )));
-            }
-        },
+        Opcode::TlsValue => implemented_in_isle(ctx),
 
         Opcode::SqmulRoundSat => implemented_in_isle(ctx),
 

cranelift/codegen/src/machinst/lower.rs

@@ -1026,20 +1026,6 @@ impl<'func, I: VCodeInst> Lower<'func, I> {
         &self.f.dfg[ir_inst]
     }
 
-    /// Get the symbol name, relocation distance estimate, and offset for a
-    /// symbol_value instruction.
-    pub fn symbol_value<'b>(
-        &'b self,
-        ir_inst: Inst,
-    ) -> Option<(&'b ExternalName, RelocDistance, i64)> {
-        match &self.f.dfg[ir_inst] {
-            &InstructionData::UnaryGlobalValue { global_value, .. } => {
-                self.symbol_value_data(global_value)
-            }
-            _ => None,
-        }
-    }
-
     /// Likewise, but starting with a GlobalValue identifier.
     pub fn symbol_value_data<'b>(
         &'b self,