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Fix SQRT.S operand selection in the FPU translator #277

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Fix SQRT.S operand selection in the FPU translator #277

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3 changes: 2 additions & 1 deletion ps2xRecomp/src/lib/fpu_translator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,8 @@ namespace ps2recomp
"ctx->f[{}] = FPU_DIV_S(ctx->f[{}], ctx->f[{}]); }}",
ft, fd, fs, ft);
case COP1_S_SQRT:
return fmt::format("ctx->f[{}] = FPU_SQRT_S(ctx->f[{}]);", fd, fs);
// SQRT.S fd, ft reads the ft field; fs is 0 in the encoding.
return fmt::format("ctx->f[{}] = FPU_SQRT_S(ctx->f[{}]);", fd, ft);
case COP1_S_ABS:
return fmt::format("ctx->f[{}] = FPU_ABS_S(ctx->f[{}]);", fd, fs);
case COP1_S_MOV:
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20 changes: 20 additions & 0 deletions ps2xTest/src/code_generator_tests.cpp
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Expand Up @@ -1020,6 +1020,26 @@ void register_code_generator_tests()
t.IsTrue(ctc1Code.find("ignored") == std::string::npos, "CTC1 FCR31 should not be ignored");
});

tc.Run("SQRT.S reads the ft operand", [](TestCase &t) {
CodeGenerator gen({}, {});

// sqrt.s $f2, $f2 (0x46020084): fs field is 0, the source is ft
Instruction sqrtS{};
sqrtS.raw = 0x46020084;
sqrtS.opcode = OPCODE_COP1;
sqrtS.rs = COP1_S;
sqrtS.rt = 2;
sqrtS.rd = 0;
sqrtS.sa = 2;
sqrtS.function = COP1_S_SQRT;

std::string sqrtCode = gen.translateInstruction(sqrtS);
printGeneratedCode("SQRT.S reads the ft operand", sqrtCode);
t.IsTrue(sqrtCode.find("ctx->f[2] = FPU_SQRT_S(ctx->f[2])") != std::string::npos,
"SQRT.S should take the square root of ft");
t.IsTrue(sqrtCode.find("ctx->f[0]") == std::string::npos, "SQRT.S must not read fs");
});

tc.Run("VU CFC2/CTC2 access VI registers directly", [](TestCase& t)
{
CodeGenerator gen({}, {});
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