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

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

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7 changes: 5 additions & 2 deletions ps2xRecomp/src/lib/fpu_translator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,9 @@ namespace ps2recomp
"else ctx->f[{}] = ctx->f[{}] / ctx->f[{}];",
ft, fd, fs, fd, fs, ft);
case COP1_S_SQRT:
return fmt::format("ctx->f[{}] = FPU_SQRT_S(ctx->f[{}]);", fd, fs);
// R5900: SQRT.S fd, ft takes its source from ft (the fs field is 0).
// Negative inputs use the magnitude (PCSX2 FPU.cpp SQRT_S).
return fmt::format("ctx->f[{}] = FPU_SQRT_S(fabsf(ctx->f[{}]));", fd, ft);
case COP1_S_ABS:
return fmt::format("ctx->f[{}] = FPU_ABS_S(ctx->f[{}]);", fd, fs);
case COP1_S_MOV:
Expand All @@ -76,7 +78,8 @@ namespace ps2recomp
case COP1_S_CVT_W:
return fmt::format("{{ int32_t tmp = FPU_CVT_W_S(ctx->f[{}]); std::memcpy(&ctx->f[{}], &tmp, sizeof(tmp)); }}", fs, fd);
case COP1_S_RSQRT:
return fmt::format("ctx->f[{}] = 1.0f / sqrtf(ctx->f[{}]);", fd, fs);
// R5900: RSQRT.S fd, fs, ft computes fs / sqrt(|ft|).
return fmt::format("ctx->f[{}] = ctx->f[{}] / sqrtf(fabsf(ctx->f[{}]));", fd, fs, ft);
case COP1_S_ADDA:
return fmt::format("FPU_SET_ACC(ctx, FPU_ADD_S(ctx->f[{}], ctx->f[{}]));", fs, ft);
case COP1_S_SUBA:
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34 changes: 34 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 @@ -1020,6 +1020,40 @@ void register_code_generator_tests()
t.IsTrue(ctc1Code.find("ignored") == std::string::npos, "CTC1 FCR31 should not be ignored");
});

tc.Run("SQRT.S/RSQRT.S use 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/RSQRT.S use the ft operand (SQRT.S)", sqrtCode);
t.IsTrue(sqrtCode.find("ctx->f[2] = FPU_SQRT_S(fabsf(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");

// rsqrt.s $f1, $f3, $f4: fd = fs / sqrt(|ft|)
Instruction rsqrtS{};
rsqrtS.opcode = OPCODE_COP1;
rsqrtS.rs = COP1_S;
rsqrtS.rt = 4;
rsqrtS.rd = 3;
rsqrtS.sa = 1;
rsqrtS.function = COP1_S_RSQRT;

std::string rsqrtCode = gen.translateInstruction(rsqrtS);
printGeneratedCode("SQRT.S/RSQRT.S use the ft operand (RSQRT.S)", rsqrtCode);
t.IsTrue(rsqrtCode.find("ctx->f[1] = ctx->f[3] / sqrtf(fabsf(ctx->f[4]))") != std::string::npos,
"RSQRT.S should compute fs / sqrt(|ft|)");
});

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