ZJIT: Delete Insn::CPushAll and Insn::CPopAll

Since we automatically preserve registers across calls, it's never
necessary to manually and imprecisely do it with `C{Push,Pop}All`.
Delete them to remove the maintenance burden and reduce confusion.

Author: XrXr

zjit/src/backend/arm64/mod.rs

@@ -1426,28 +1426,6 @@ impl Assembler {
                 Insn::CPopInto(opnd) => {
                     emit_pop(cb, opnd.into());
                 },
-                Insn::CPushAll => {
-                    let regs = Assembler::get_caller_save_regs();
-
-                    for reg in regs {
-                        emit_push(cb, A64Opnd::Reg(reg));
-                    }
-
-                    // Push the flags/state register
-                    mrs(cb, Self::EMIT_OPND, SystemRegister::NZCV);
-                    emit_push(cb, Self::EMIT_OPND);
-                },
-                Insn::CPopAll => {
-                    let regs = Assembler::get_caller_save_regs();
-
-                    // Pop the state/flags register
-                    msr(cb, SystemRegister::NZCV, Self::EMIT_OPND);
-                    emit_pop(cb, Self::EMIT_OPND);
-
-                    for reg in regs.into_iter().rev() {
-                        emit_pop(cb, A64Opnd::Reg(reg));
-                    }
-                },
                 Insn::CCall { fptr, .. } => {
                     match fptr {
                         Opnd::UImm(fptr) => {
@@ -1881,50 +1859,6 @@ mod tests {
         assert_snapshot!(cb.hexdump(), @"48656c6c6f2c20776f726c6421000000");
     }
 
-    #[test]
-    fn test_emit_cpush_all() {
-        let (mut asm, mut cb) = setup_asm();
-
-        asm.cpush_all();
-        asm.compile_with_num_regs(&mut cb, 0);
-
-        assert_disasm_snapshot!(cb.disasm(), @r"
-        0x0: str x1, [sp, #-0x10]!
-        0x4: str x9, [sp, #-0x10]!
-        0x8: str x10, [sp, #-0x10]!
-        0xc: str x11, [sp, #-0x10]!
-        0x10: str x12, [sp, #-0x10]!
-        0x14: str x13, [sp, #-0x10]!
-        0x18: str x14, [sp, #-0x10]!
-        0x1c: str x15, [sp, #-0x10]!
-        0x20: mrs x16, nzcv
-        0x24: str x16, [sp, #-0x10]!
-        ");
-        assert_snapshot!(cb.hexdump(), @"e10f1ff8e90f1ff8ea0f1ff8eb0f1ff8ec0f1ff8ed0f1ff8ee0f1ff8ef0f1ff810423bd5f00f1ff8");
-    }
-
-    #[test]
-    fn test_emit_cpop_all() {
-        let (mut asm, mut cb) = setup_asm();
-
-        asm.cpop_all();
-        asm.compile_with_num_regs(&mut cb, 0);
-
-        assert_disasm_snapshot!(cb.disasm(), @r"
-        0x0: msr nzcv, x16
-        0x4: ldr x16, [sp], #0x10
-        0x8: ldr x15, [sp], #0x10
-        0xc: ldr x14, [sp], #0x10
-        0x10: ldr x13, [sp], #0x10
-        0x14: ldr x12, [sp], #0x10
-        0x18: ldr x11, [sp], #0x10
-        0x1c: ldr x10, [sp], #0x10
-        0x20: ldr x9, [sp], #0x10
-        0x24: ldr x1, [sp], #0x10
-        ");
-        assert_snapshot!(cb.hexdump(), @"10421bd5f00741f8ef0741f8ee0741f8ed0741f8ec0741f8eb0741f8ea0741f8e90741f8e10741f8");
-    }
-
     #[test]
     fn test_emit_frame() {
         let (mut asm, mut cb) = setup_asm();

zjit/src/backend/lir.rs

@@ -377,18 +377,12 @@ pub enum Insn {
     /// Pop a register from the C stack
     CPop { out: Opnd },
 
-    /// Pop all of the caller-save registers and the flags from the C stack
-    CPopAll,
-
     /// Pop a register from the C stack and store it into another register
     CPopInto(Opnd),
 
     /// Push a register onto the C stack
     CPush(Opnd),
 
-    /// Push all of the caller-save registers and the flags to the C stack
-    CPushAll,
-
     // C function call with N arguments (variadic)
     CCall {
         opnds: Vec<Opnd>,
@@ -614,10 +608,8 @@ impl Insn {
             Insn::Comment(_) => "Comment",
             Insn::Cmp { .. } => "Cmp",
             Insn::CPop { .. } => "CPop",
-            Insn::CPopAll => "CPopAll",
             Insn::CPopInto(_) => "CPopInto",
             Insn::CPush(_) => "CPush",
-            Insn::CPushAll => "CPushAll",
             Insn::CCall { .. } => "CCall",
             Insn::CRet(_) => "CRet",
             Insn::CSelE { .. } => "CSelE",
@@ -851,8 +843,6 @@ impl<'a> Iterator for InsnOpndIterator<'a> {
             Insn::Breakpoint |
             Insn::Comment(_) |
             Insn::CPop { .. } |
-            Insn::CPopAll |
-            Insn::CPushAll |
             Insn::PadPatchPoint |
             Insn::PosMarker(_) => None,
 
@@ -1020,8 +1010,6 @@ impl<'a> InsnOpndMutIterator<'a> {
             Insn::Breakpoint |
             Insn::Comment(_) |
             Insn::CPop { .. } |
-            Insn::CPopAll |
-            Insn::CPushAll |
             Insn::FrameSetup { .. } |
             Insn::FrameTeardown { .. } |
             Insn::PadPatchPoint |
@@ -1867,10 +1855,7 @@ impl Assembler
                     }
 
                     if should_record_exit {
-                        // Preserve caller-saved registers that may be used in the shared exit.
-                        self.cpush_all();
                         asm_ccall!(self, rb_zjit_record_exit_stack, pc);
-                        self.cpop_all();
                     }
 
                     // If the side exit has already been compiled, jump to it.
@@ -2135,10 +2120,6 @@ impl Assembler {
         out
     }
 
-    pub fn cpop_all(&mut self) {
-        self.push_insn(Insn::CPopAll);
-    }
-
     pub fn cpop_into(&mut self, opnd: Opnd) {
         assert!(matches!(opnd, Opnd::Reg(_)), "Destination of cpop_into must be a register, got: {opnd:?}");
         self.push_insn(Insn::CPopInto(opnd));
@@ -2148,10 +2129,6 @@ impl Assembler {
         self.push_insn(Insn::CPush(opnd));
     }
 
-    pub fn cpush_all(&mut self) {
-        self.push_insn(Insn::CPushAll);
-    }
-
     pub fn cret(&mut self, opnd: Opnd) {
         self.push_insn(Insn::CRet(opnd));
     }

zjit/src/backend/x86_64/mod.rs

@@ -858,25 +858,6 @@ impl Assembler {
                     pop(cb, opnd.into());
                 },
 
-                // Push and pop to the C stack all caller-save registers and the
-                // flags
-                Insn::CPushAll => {
-                    let regs = Assembler::get_caller_save_regs();
-
-                    for reg in regs {
-                        push(cb, X86Opnd::Reg(reg));
-                    }
-                    pushfq(cb);
-                },
-                Insn::CPopAll => {
-                    let regs = Assembler::get_caller_save_regs();
-
-                    popfq(cb);
-                    for reg in regs.into_iter().rev() {
-                        pop(cb, X86Opnd::Reg(reg));
-                    }
-                },
-
                 // C function call
                 Insn::CCall { fptr, .. } => {
                     match fptr {