interpreter: add handling for a branch in delay slot

diff --git a/libpcsxcore/psxinterpreter.c b/libpcsxcore/psxinterpreter.c
index 08b656f..3736b23 100644 (file)
--- a/libpcsxcore/psxinterpreter.c
+++ b/libpcsxcore/psxinterpreter.c
@@ -273,6 +273,128 @@ void psxDelayTest(int reg, u32 bpc) {
        psxBranchTest();
 }
 
+static u32 psxBranchNoDelay(void) {
+       u32 *code;
+       u32 temp;
+
+       code = (u32 *)PSXM(psxRegs.pc);
+       psxRegs.code = ((code == NULL) ? 0 : SWAP32(*code));
+       switch (_Op_) {
+               case 0x00: // SPECIAL
+                       switch (_Funct_) {
+                               case 0x08: // JR
+                                       return _u32(_rRs_);
+                               case 0x09: // JALR
+                                       temp = _u32(_rRs_);
+                                       if (_Rd_) { _SetLink(_Rd_); }
+                                       return temp;
+                       }
+                       break;
+               case 0x01: // REGIMM
+                       switch (_Rt_) {
+                               case 0x00: // BLTZ
+                                       if (_i32(_rRs_) < 0)
+                                               return _BranchTarget_;
+                                       break;
+                               case 0x01: // BGEZ
+                                       if (_i32(_rRs_) >= 0)
+                                               return _BranchTarget_;
+                                       break;
+                               case 0x08: // BLTZAL
+                                       if (_i32(_rRs_) < 0) {
+                                               _SetLink(31);
+                                               return _BranchTarget_;
+                                       }
+                                       break;
+                               case 0x09: // BGEZAL
+                                       if (_i32(_rRs_) >= 0) {
+                                               _SetLink(31);
+                                               return _BranchTarget_;
+                                       }
+                                       break;
+                       }
+                       break;
+               case 0x02: // J
+                       return _JumpTarget_;
+               case 0x03: // JAL
+                       _SetLink(31);
+                       return _JumpTarget_;
+               case 0x04: // BEQ
+                       if (_i32(_rRs_) == _i32(_rRt_))
+                               return _BranchTarget_;
+                       break;
+               case 0x05: // BNE
+                       if (_i32(_rRs_) != _i32(_rRt_))
+                               return _BranchTarget_;
+                       break;
+               case 0x06: // BLEZ
+                       if (_i32(_rRs_) <= 0)
+                               return _BranchTarget_;
+                       break;
+               case 0x07: // BGTZ
+                       if (_i32(_rRs_) > 0)
+                               return _BranchTarget_;
+                       break;
+       }
+
+       return (u32)-1;
+}
+
+static int psxDelayBranchExec(u32 tar) {
+       execI();
+
+       branch = 0;
+       psxRegs.pc = tar;
+       psxRegs.cycle += BIAS;
+       psxBranchTest();
+       return 1;
+}
+
+static int psxDelayBranchTest(u32 tar1) {
+       u32 tar2, tmp1, tmp2;
+
+       tar2 = psxBranchNoDelay();
+       if (tar2 == (u32)-1)
+               return 0;
+
+       debugI();
+
+       /*
+        * Branch in delay slot:
+        * - execute 1 instruction at tar1
+        * - jump to tar2 (target of branch in delay slot; this branch
+        *   has no normal delay slot, instruction at tar1 was fetched instead)
+        */
+       psxRegs.pc = tar1;
+       tmp1 = psxBranchNoDelay();
+       if (tmp1 == (u32)-1) {
+               return psxDelayBranchExec(tar2);
+       }
+       debugI();
+       psxRegs.cycle += BIAS;
+
+       /*
+        * Got a branch at tar1:
+        * - execute 1 instruction at tar2
+        * - jump to target of that branch (tmp1)
+        */
+       psxRegs.pc = tar2;
+       tmp2 = psxBranchNoDelay();
+       if (tmp2 == (u32)-1) {
+               return psxDelayBranchExec(tmp1);
+       }
+       debugI();
+       psxRegs.cycle += BIAS;
+
+       /*
+        * Got a branch at tar2:
+        * - execute 1 instruction at tmp1
+        * - jump to target of that branch (tmp2)
+        */
+       psxRegs.pc = tmp1;
+       return psxDelayBranchExec(tmp2);
+}
+
 __inline void doBranch(u32 tar) {
        u32 *code;
        u32 tmp;
@@ -280,6 +402,10 @@ __inline void doBranch(u32 tar) {
        branch2 = branch = 1;
        branchPC = tar;
 
+       // check for branch in delay slot
+       if (psxDelayBranchTest(tar))
+               return;
+
        code = (u32 *)PSXM(psxRegs.pc);
        psxRegs.code = ((code == NULL) ? 0 : SWAP32(*code));