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mips3: Ensure there is at least 1 cycle to be counted after reading Count. Without this, some timing loops won't exit to the scheduler until they complete.

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This commit is contained in:
Aaron Giles 2021-04-22 08:49:31 -07:00
parent a27f59b81a
commit 08688e3083
1 changed files with 12 additions and 0 deletions
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12
src/devices/cpu/mips/mips3drc.cpp
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@ -2460,6 +2460,11 @@ bool mips3_device::generate_set_cop0_reg(drcuml_block &block, compiler_state &co
return true;
case COP0_Count:
// don't count the cycle for this instruction yet; we need a non-zero cycle
// count in case we are in a delay slot, otherwise the test for negative cycles
// won't be generated (due to compiler.cycles == 0); see the loop during early
// boot of gauntdl, @BFC01A24
compiler.cycles--;
generate_update_cycles(block, compiler, desc->pc, !in_delay_slot); // <subtract cycles>
UML_MOV(block, CPR032(COP0_Count), I0); // mov [Count],i0
UML_CALLC(block, cfunc_get_cycles, this); // callc cfunc_get_cycles,mips3
@ -2468,6 +2473,7 @@ bool mips3_device::generate_set_cop0_reg(drcuml_block &block, compiler_state &co
UML_DSUB(block, mem(&m_core->count_zero_time), mem(&m_core->numcycles), I0);
// dsub [count_zero_time],[m_numcycles],i0
UML_CALLC(block, cfunc_mips3com_update_cycle_counting, this); // callc mips3com_update_cycle_counting,mips.core
compiler.cycles++;
return true;
case COP0_Compare:
@ -2513,12 +2519,18 @@ bool mips3_device::generate_get_cop0_reg(drcuml_block &block, compiler_state &co
switch (reg)
{
case COP0_Count:
// don't count the cycle for this instruction yet; we need a non-zero cycle
// count in case we are in a delay slot, otherwise the test for negative cycles
// won't be generated (due to compiler.cycles == 0); see the loop during early
// boot of gauntdl, @BFC01A24
compiler.cycles--;
generate_update_cycles(block, compiler, desc->pc, false); // <subtract cycles>
UML_CALLC(block, cfunc_get_cycles, this); // callc cfunc_get_cycles,mips3
UML_DSUB(block, I0, mem(&m_core->numcycles), mem(&m_core->count_zero_time));
// dsub i0,[numcycles],[count_zero_time]
UML_DSHR(block, I0, I0, 1); // dshr i0,i0,1
UML_DSEXT(block, I0, I0, SIZE_DWORD); // dsext i0,i0,dword
compiler.cycles++;
return true;
case COP0_Random: