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fix(recomp): start VCALLMSR from CMSAR0 instead of indexing vi[] #268

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fix(recomp): start VCALLMSR from CMSAR0 instead of indexing vi[] #268

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21 changes: 10 additions & 11 deletions ps2xRecomp/src/lib/vu_translation_helpers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -164,17 +164,16 @@ namespace ps2recomp

std::string CodeGenerator::translateVU_VCALLMSR(const Instruction &inst)
{
// VCALLMSR calls a VU0 microprogram at address stored in integer register
uint8_t vis_reg_idx = inst.rd; // Source integer register (vis)

return fmt::format(
"{{ "
" uint16_t instr_index = ctx->vi[{}] & 0x1FF; " // Get instruction index from VI[IS], mask to 9 bits
" uint32_t target_byte_addr = (uint32_t)instr_index << 3; " // Convert to byte address
" ctx->vu0_pc = target_byte_addr; "
" runtime->vu0StartMicroProgram(rdram, ctx, target_byte_addr); "
"}}",
vis_reg_idx);
// VCALLMSR calls a VU0 microprogram at the address held in CMSAR0. CMSAR0 is VU0 control register 27
// (written by CTC2 $vi27, see VU0_CR_CMSAR0), not one of the 16 VI registers, so it lives in ctx->vu0_cmsar0.
(void)inst;

return "{ "
" uint16_t instr_index = (uint16_t)(ctx->vu0_cmsar0 & 0x1FF); " // Get instruction index from CMSAR0, mask to 9 bits
" uint32_t target_byte_addr = (uint32_t)instr_index << 3; " // Convert to byte address
" ctx->vu0_pc = target_byte_addr; "
" runtime->vu0StartMicroProgram(rdram, ctx, target_byte_addr); "
"}";
}

std::string CodeGenerator::translateVU_VRNEXT(const Instruction &inst)
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19 changes: 19 additions & 0 deletions ps2xTest/src/code_generator_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2035,6 +2035,25 @@ void register_code_generator_tests()
"VRXOR should keep the LFSR comment on its own line");
});

tc.Run("VCALLMSR starts the microprogram from CMSAR0, not a VI array slot", [](TestCase &t) {
CodeGenerator gen({}, {});

// VCALLMSR has no register operand; $vi27 in the assembly is CMSAR0 (VU0 control register 27).
Instruction inst{};
inst.opcode = OPCODE_COP2;
inst.function = VU0_S1_VCALLMSR;
inst.rd = 27;

const std::string generated = gen.translateVU_VCALLMSR(inst);
printGeneratedCode("VCALLMSR starts the microprogram from CMSAR0, not a VI array slot", generated);
t.IsTrue(generated.find("ctx->vu0_cmsar0") != std::string::npos,
"VCALLMSR should read the start address from CMSAR0");
t.IsTrue(generated.find("ctx->vi[") == std::string::npos,
"VCALLMSR must not index the 16-entry vi[] array with a control register number");
t.IsTrue(generated.find("runtime->vu0StartMicroProgram(") != std::string::npos,
"VCALLMSR should still start the VU0 microprogram");
});

tc.Run("resolveStubTarget allows leading underscore alias", [](TestCase &t) {
t.Equals(PS2Recompiler::resolveStubTarget("_rand"), StubTarget::Stub,
"_rand should resolve via rand stub alias");
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