s390x: Hard code the link register in all call and return instructions

cranelift/bforest/src/node.rs

@@ -13,7 +13,6 @@ use core::fmt;
 ///
 /// An inner node contains at least M/2 node references unless it is the right-most node at its
 /// level. A leaf node contains at least N/2 keys unless it is the right-most leaf.
-#[allow(dead_code)] // workaround for https://github.com/rust-lang/rust/issues/64362
 pub(super) enum NodeData<F: Forest> {
     Inner {
         /// The number of keys in this node.

cranelift/codegen/src/isa/riscv64/inst/imms.rs

@@ -2,7 +2,6 @@
 
 // Some variants are never constructed, but we still want them as options in the future.
 use super::Inst;
-#[allow(dead_code)]
 use std::fmt::{Debug, Display, Formatter, Result};
 
 #[derive(Copy, Clone, Debug, Default)]

cranelift/codegen/src/isa/s390x/abi.rs

@@ -638,7 +638,7 @@ impl ABIMachineSpec for S390xMachineDeps {
         _isa_flags: &s390x_settings::Flags,
         _frame_layout: &FrameLayout,
     ) -> SmallInstVec<Inst> {
-        smallvec![Inst::Ret { link: gpr(14) }]
+        smallvec![Inst::Ret]
     }
 
     fn gen_probestack(_insts: &mut SmallInstVec<Self::I>, _: u32) {

cranelift/codegen/src/isa/s390x/inst.isle

@@ -893,12 +893,10 @@
 
     ;; A machine call instruction.
     (Call
-      (link WritableReg)
       (info BoxCallInfo))
 
     ;; A machine indirect-call instruction.
     (CallInd
-      (link WritableReg)
       (info BoxCallIndInfo))
 
     ;; A machine tail call instruction.
@@ -920,8 +918,7 @@
     ;; ---- branches (exactly one must appear at end of BB) ----
 
     ;; A machine return instruction.
-    (Ret
-      (link Reg))
+    (Ret)
 
     ;; An unconditional branch.
     (Jump
@@ -1021,7 +1018,6 @@
       (tls_offset WritableReg)
       (got Reg)
       (got_offset Reg)
-      (link WritableReg)
       (symbol BoxSymbolReloc))
 ))
 
@@ -2699,14 +2695,14 @@
         dst))
 
 ;; Helper for emitting `MInst.Call` instructions.
-(decl call_impl (WritableReg BoxCallInfo) SideEffectNoResult)
-(rule (call_impl reg info)
-      (SideEffectNoResult.Inst (MInst.Call reg info)))
+(decl call_impl (BoxCallInfo) SideEffectNoResult)
+(rule (call_impl info)
+      (SideEffectNoResult.Inst (MInst.Call info)))
 
 ;; Helper for emitting `MInst.CallInd` instructions.
-(decl call_ind_impl (WritableReg BoxCallIndInfo) SideEffectNoResult)
-(rule (call_ind_impl reg info)
-      (SideEffectNoResult.Inst (MInst.CallInd reg info)))
+(decl call_ind_impl (BoxCallIndInfo) SideEffectNoResult)
+(rule (call_ind_impl info)
+      (SideEffectNoResult.Inst (MInst.CallInd info)))
 
 ;; Helper for emitting `MInst.ReturnCall` instructions.
 (decl return_call_impl (BoxReturnCallInfo) SideEffectNoResult)
@@ -3581,16 +3577,13 @@
 (decl abi_return_call_stack_args (Sig) MemArg)
 (extern constructor abi_return_call_stack_args abi_return_call_stack_args)
 
-(decl writable_link_reg () WritableReg)
-(rule (writable_link_reg) (writable_gpr 14))
-
 (decl abi_call (Sig ExternalName CallArgList CallRetList) SideEffectNoResult)
 (rule (abi_call abi name uses defs)
-      (call_impl (writable_link_reg) (abi_call_info abi name uses defs)))
+      (call_impl (abi_call_info abi name uses defs)))
 
 (decl abi_call_ind (Sig Reg CallArgList CallRetList) SideEffectNoResult)
 (rule (abi_call_ind abi target uses defs)
-      (call_ind_impl (writable_link_reg) (abi_call_ind_info abi target uses defs)))
+      (call_ind_impl (abi_call_ind_info abi target uses defs)))
 
 (decl abi_return_call (Sig ExternalName CallArgList) SideEffectNoResult)
 (rule (abi_return_call abi name uses)
@@ -3613,7 +3606,7 @@
 
 (decl lib_call (BoxCallInfo) SideEffectNoResult)
 (rule (lib_call info)
-      (call_impl (writable_link_reg) info))
+      (call_impl info))
 
 
 ;; Helpers for generating vector pack and unpack instructions ;;;;;;;;;;;;;;;;;;

cranelift/codegen/src/isa/s390x/inst/emit.rs

@@ -3257,9 +3257,7 @@ impl Inst {
                 inst.emit(sink, emit_info, state);
                 state.nominal_sp_offset += size;
             }
-            &Inst::Call { link, ref info } => {
-                debug_assert_eq!(link.to_reg(), gpr(14));
-
+            &Inst::Call { ref info } => {
                 let opcode = 0xc05; // BRASL
 
                 // Add relocation for target function.  This has to be done *before*
@@ -3272,21 +3270,19 @@ impl Inst {
                     sink.push_user_stack_map(state, offset, s);
                 }
 
-                put(sink, &enc_ril_b(opcode, link.to_reg(), 0));
+                put(sink, &enc_ril_b(opcode, link_reg(), 0));
                 sink.add_call_site();
 
                 state.nominal_sp_offset -= info.callee_pop_size;
             }
-            &Inst::CallInd { link, ref info } => {
-                debug_assert_eq!(link.to_reg(), gpr(14));
-
+            &Inst::CallInd { ref info } => {
                 if let Some(s) = state.take_stack_map() {
                     let offset = sink.cur_offset() + 2;
                     sink.push_user_stack_map(state, offset, s);
                 }
 
                 let opcode = 0x0d; // BASR
-                put(sink, &enc_rr(opcode, link.to_reg(), info.dest));
+                put(sink, &enc_rr(opcode, link_reg(), info.dest));
                 sink.add_call_site();
 
                 state.nominal_sp_offset -= info.callee_pop_size;
@@ -3319,11 +3315,7 @@ impl Inst {
                 put(sink, &enc_rr(opcode, gpr(15), rn));
                 sink.add_call_site();
             }
-            &Inst::ElfTlsGetOffset {
-                ref symbol, link, ..
-            } => {
-                debug_assert_eq!(link.to_reg(), gpr(14));
-
+            &Inst::ElfTlsGetOffset { ref symbol, .. } => {
                 let opcode = 0xc05; // BRASL
 
                 // Add relocation for target function. This has to be done
@@ -3341,10 +3333,9 @@ impl Inst {
             }
             &Inst::Args { .. } => {}
             &Inst::Rets { .. } => {}
-            &Inst::Ret { link } => {
-                debug_assert_eq!(link, gpr(14));
+            &Inst::Ret => {
                 let opcode = 0x07; // BCR
-                put(sink, &enc_rr(opcode, gpr(15), link));
+                put(sink, &enc_rr(opcode, gpr(15), link_reg()));
             }
             &Inst::Jump { dest } => {
                 let off = sink.cur_offset();

cranelift/codegen/src/isa/s390x/inst/emit_tests.rs

@@ -6982,7 +6982,6 @@ fn test_s390x_binemit() {
 
     insns.push((
         Inst::Call {
-            link: writable_gpr(14),
             info: Box::new(CallInfo::empty(
                 ExternalName::testcase("test0"),
                 CallConv::SystemV,
@@ -6994,14 +6993,13 @@ fn test_s390x_binemit() {
 
     insns.push((
         Inst::CallInd {
-            link: writable_gpr(14),
             info: Box::new(CallInfo::empty(gpr(1), CallConv::SystemV)),
         },
         "0DE1",
         "basr %r14, %r1",
     ));
 
-    insns.push((Inst::Ret { link: gpr(14) }, "07FE", "br %r14"));
+    insns.push((Inst::Ret, "07FE", "br %r14"));
 
     insns.push((Inst::Debugtrap, "0001", ".word 0x0001 # debugtrap"));
 

cranelift/codegen/src/isa/s390x/inst/mod.rs

@@ -873,7 +873,7 @@ fn s390x_get_operands(inst: &mut Inst, collector: &mut DenyReuseVisitor<impl Ope
             collector.reg_use(rn);
         }
         Inst::AllocateArgs { .. } => {}
-        Inst::Call { link, info, .. } => {
+        Inst::Call { info } => {
             let CallInfo {
                 uses,
                 defs,
@@ -884,14 +884,14 @@ fn s390x_get_operands(inst: &mut Inst, collector: &mut DenyReuseVisitor<impl Ope
                 collector.reg_fixed_use(vreg, *preg);
             }
             let mut clobbers = *clobbers;
-            clobbers.add(link.to_reg().to_real_reg().unwrap().into());
+            clobbers.add(link_reg().to_real_reg().unwrap().into());
             for CallRetPair { vreg, preg } in defs {
                 clobbers.remove(PReg::from(preg.to_real_reg().unwrap()));
                 collector.reg_fixed_def(vreg, *preg);
             }
             collector.reg_clobbers(clobbers);
         }
-        Inst::CallInd { link, info } => {
+        Inst::CallInd { info } => {
             let CallInfo {
                 dest,
                 uses,
@@ -904,7 +904,7 @@ fn s390x_get_operands(inst: &mut Inst, collector: &mut DenyReuseVisitor<impl Ope
                 collector.reg_fixed_use(vreg, *preg);
             }
             let mut clobbers = *clobbers;
-            clobbers.add(link.to_reg().to_real_reg().unwrap().into());
+            clobbers.add(link_reg().to_real_reg().unwrap().into());
             for CallRetPair { vreg, preg } in defs {
                 clobbers.remove(PReg::from(preg.to_real_reg().unwrap()));
                 collector.reg_fixed_def(vreg, *preg);
@@ -928,15 +928,14 @@ fn s390x_get_operands(inst: &mut Inst, collector: &mut DenyReuseVisitor<impl Ope
             tls_offset,
             got,
             got_offset,
-            link,
             ..
         } => {
             collector.reg_fixed_use(got, gpr(12));
             collector.reg_fixed_use(got_offset, gpr(2));
             collector.reg_fixed_def(tls_offset, gpr(2));
 
             let mut clobbers = S390xMachineDeps::get_regs_clobbered_by_call(CallConv::SystemV);
-            clobbers.add(link.to_reg().to_real_reg().unwrap().into());
+            clobbers.add(link_reg().to_real_reg().unwrap().into());
             clobbers.remove(gpr_preg(2));
             collector.reg_clobbers(clobbers);
         }
@@ -1063,8 +1062,8 @@ impl MachInst for Inst {
         // registers.
         match self {
             &Inst::Args { .. } => false,
-            &Inst::Call { ref info, .. } => info.caller_conv != info.callee_conv,
-            &Inst::CallInd { ref info, .. } => info.caller_conv != info.callee_conv,
+            &Inst::Call { ref info } => info.caller_conv != info.callee_conv,
+            &Inst::CallInd { ref info } => info.caller_conv != info.callee_conv,
             &Inst::ElfTlsGetOffset { .. } => false,
             _ => true,
         }
@@ -3141,31 +3140,27 @@ impl Inst {
                     format!("slgfi {}, {}", show_reg(stack_reg()), size)
                 }
             }
-            &Inst::Call { link, ref info } => {
-                let link = link.to_reg();
+            &Inst::Call { ref info } => {
                 let callee_pop_size = if info.callee_pop_size > 0 {
                     format!(" ; callee_pop_size {}", info.callee_pop_size)
                 } else {
                     "".to_string()
                 };
-                debug_assert_eq!(link, gpr(14));
                 format!(
                     "brasl {}, {}{}",
-                    show_reg(link),
+                    show_reg(link_reg()),
                     info.dest.display(None),
                     callee_pop_size
                 )
             }
-            &Inst::CallInd { link, ref info, .. } => {
-                let link = link.to_reg();
+            &Inst::CallInd { ref info, .. } => {
                 let rn = pretty_print_reg(info.dest);
                 let callee_pop_size = if info.callee_pop_size > 0 {
                     format!(" ; callee_pop_size {}", info.callee_pop_size)
                 } else {
                     "".to_string()
                 };
-                debug_assert_eq!(link, gpr(14));
-                format!("basr {}, {}{}", show_reg(link), rn, callee_pop_size)
+                format!("basr {}, {}{}", show_reg(link_reg()), rn, callee_pop_size)
             }
             &Inst::ReturnCall { ref info } => {
                 let callee_pop_size = if info.callee_pop_size > 0 {
@@ -3184,20 +3179,14 @@ impl Inst {
                 };
                 format!("return_call_ind {rn}{callee_pop_size}")
             }
-            &Inst::ElfTlsGetOffset {
-                ref symbol,
-                ref link,
-                ..
-            } => {
-                let link = link.to_reg();
+            &Inst::ElfTlsGetOffset { ref symbol, .. } => {
                 let dest = match &**symbol {
                     SymbolReloc::TlsGd { name } => {
                         format!("tls_gdcall:{}", name.display(None))
                     }
                     _ => unreachable!(),
                 };
-                debug_assert_eq!(link, gpr(14));
-                format!("brasl {}, {}", show_reg(link), dest)
+                format!("brasl {}, {}", show_reg(link_reg()), dest)
             }
             &Inst::Args { ref args } => {
                 let mut s = "args".to_string();
@@ -3217,9 +3206,8 @@ impl Inst {
                 }
                 s
             }
-            &Inst::Ret { link } => {
-                debug_assert_eq!(link, gpr(14));
-                let link = show_reg(link);
+            &Inst::Ret => {
+                let link = show_reg(link_reg());
                 format!("br {link}")
             }
             &Inst::Jump { dest } => {

cranelift/codegen/src/isa/s390x/inst/regs.rs

@@ -78,6 +78,10 @@ pub fn zero_reg() -> Reg {
     gpr(0)
 }
 
+pub fn link_reg() -> Reg {
+    gpr(14)
+}
+
 pub fn show_reg(reg: Reg) -> String {
     if let Some(rreg) = reg.to_real_reg() {
         match rreg.class() {

cranelift/codegen/src/isa/s390x/lower.isle

@@ -2279,7 +2279,7 @@
 (rule (lib_call_tls_get_offset got got_offset symbol)
       (let ((tls_offset WritableReg (temp_writable_reg $I64))
             (_ Unit (abi_for_elf_tls_get_offset))
-            (_ Unit (emit (MInst.ElfTlsGetOffset tls_offset got got_offset (writable_link_reg) symbol))))
+            (_ Unit (emit (MInst.ElfTlsGetOffset tls_offset got got_offset symbol))))
         tls_offset))
 
 (decl abi_for_elf_tls_get_offset () Unit)