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122 lines
2.8 KiB
C
122 lines
2.8 KiB
C
// The OS/K Team licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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#include <pc/arch.h>
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static bool eval_cond(ctx_t *ctx, uint cond)
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{
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bool neg = cond & (1 << 4);
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bool ok;
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cond &= ~(1 << 4);
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switch (cond)
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{
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case CD_NONE: ok = 1; break;
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case CD_C: ok = flg&CF; break;
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case CD_O: ok = flg&OF; break;
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case CD_Z: ok = flg&ZF; break;
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case CD_S: ok = flg&SF; break;
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case CD_P: ok = flg&PF; break;
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case CD_A: ok = !(flg&CF || flg&ZF); break;
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case CD_AE: ok = !(flg&CF); break;
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case CD_B: ok = flg&CF; break;
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case CD_BE: ok = flg&CF || flg&ZF; break;
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case CD_G: ok = !(flg&ZF) && (!(flg&SF) == !(flg&OF)); break;
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case CD_GE: ok = !(flg&SF) == !(flg&OF); break;
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case CD_L: ok = !(flg&SF) != !(flg&OF); break;
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case CD_LE: ok = flg&ZF || (!(flg&SF) != !(flg&OF)); break;
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case CD_CXZ: ok = !rcx; break;
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default:
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_except(ctx, E_ILL, "Invalid COND value: 0x%x", (neg?cond|(1<<4):cond));
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}
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return neg ? !ok : !!ok;
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}
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//
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// Executes an instruction
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//
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void exec_instr(ctx_t *ctx,
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instr_t *in,
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acc_t *p1,
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acc_t *p2,
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bool lock,
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bool rep,
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uint cond,
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ulong pc)
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{
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bool out;
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ulong r1 = 0, r2 = 0;
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// Debugging
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dump_instr(ctx, in, p1, p2, lock, rep, cond, pc);
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//
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// For REPs we evaluate the condition AFTER running the instruction,
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// in a do ... while(cond) fashion
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//
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if (!rep && !eval_cond(ctx, cond))
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return;
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do_rep:
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out = in->func(ctx, p1, p2, &r1, &r2);
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if (out)
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{
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if (p1->type == A_REG)
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R(p1->reg) = r1;
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else if (p1->type == A_IMM64)
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_except(ctx, E_ACC, "Trying to output to an IMM64");
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else
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{
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assert(ACC_IS_MEM(p1));
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writemem(ctx, r1, p1->addr, p1->mlen);
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}
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}
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if (out == 2)
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{
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if (p2->type == A_REG)
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R(p2->reg) = r2;
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else if (p2->type == A_IMM64)
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_except(ctx, E_ACC, "Trying to output to an IMM64");
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else
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{
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assert(ACC_IS_MEM(p2));
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writemem(ctx, r2, p2->addr, p2->mlen);
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}
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}
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if (rep)
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{
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// RCX remains untouched when condition fails
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if (!eval_cond(ctx, cond))
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return;
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if (rcx > 0)
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rcx--;
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if (rcx == 0)
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return;
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// Show that we're REP'ing
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dump_instr(ctx, in, p1, p2, lock, rep, cond, pc);
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goto do_rep;
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}
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}
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