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https://github.com/Lime3DS/Lime3DS
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shader_jit_x64_compiler: Remove ABI overhead of LG2 and EX2
This involves reimplementing log2f and exp2f.
This commit is contained in:
MerryMage
parent
235a251d3c
commit
c1aef260af
2 changed files with 185 additions and 17 deletions
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@ -432,27 +432,13 @@ void JitShader::Compile_DPH(Instruction instr) {
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void JitShader::Compile_EX2(Instruction instr) {
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Compile_SwizzleSrc(instr, 1, instr.common.src1, SRC1);
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movss(xmm0, SRC1); // ABI_PARAM1
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ABI_PushRegistersAndAdjustStack(*this, PersistentCallerSavedRegs(), 0);
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CallFarFunction(*this, exp2f);
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ABI_PopRegistersAndAdjustStack(*this, PersistentCallerSavedRegs(), 0);
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shufps(xmm0, xmm0, _MM_SHUFFLE(0, 0, 0, 0)); // ABI_RETURN
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movaps(SRC1, xmm0);
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call(exp2_subroutine);
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Compile_DestEnable(instr, SRC1);
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}
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void JitShader::Compile_LG2(Instruction instr) {
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Compile_SwizzleSrc(instr, 1, instr.common.src1, SRC1);
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movss(xmm0, SRC1); // ABI_PARAM1
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ABI_PushRegistersAndAdjustStack(*this, PersistentCallerSavedRegs(), 0);
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CallFarFunction(*this, log2f);
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ABI_PopRegistersAndAdjustStack(*this, PersistentCallerSavedRegs(), 0);
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shufps(xmm0, xmm0, _MM_SHUFFLE(0, 0, 0, 0)); // ABI_RETURN
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movaps(SRC1, xmm0);
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call(log2_subroutine);
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Compile_DestEnable(instr, SRC1);
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}
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@ -935,7 +921,179 @@ void JitShader::Compile(const std::array<u32, MAX_PROGRAM_CODE_LENGTH>* program_
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LOG_DEBUG(HW_GPU, "Compiled shader size=%lu", getSize());
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}
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JitShader::JitShader() : Xbyak::CodeGenerator(MAX_SHADER_SIZE) {}
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JitShader::JitShader() : Xbyak::CodeGenerator(MAX_SHADER_SIZE) {
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CompilePrelude();
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}
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void JitShader::CompilePrelude() {
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log2_subroutine = CompilePrelude_Log2();
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exp2_subroutine = CompilePrelude_Exp2();
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}
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Xbyak::Label JitShader::CompilePrelude_Log2() {
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Xbyak::Label subroutine;
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// SSE does not have a log instruction, thus we must approximate.
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// We perform this approximation first performaing a range reduction into the range [1.0, 2.0).
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// A minimax polynomial which was fit for the function log2(x) / (x - 1) is then evaluated.
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// We multiply the result by (x - 1) then restore the result into the appropriate range.
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// Coefficients for the minimax polynomial.
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// f(x) computes approximately log2(x) / (x - 1).
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// f(x) = c4 + x * (c3 + x * (c2 + x * (c1 + x * c0)).
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align(64);
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const void* c0 = getCurr();
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dd(0x3d74552f);
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const void* c1 = getCurr();
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dd(0xbeee7397);
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const void* c2 = getCurr();
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dd(0x3fbd96dd);
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const void* c3 = getCurr();
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dd(0xc02153f6);
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const void* c4 = getCurr();
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dd(0x4038d96c);
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align(16);
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const void* negative_infinity_vector = getCurr();
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dd(0xff800000);
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dd(0xff800000);
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dd(0xff800000);
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dd(0xff800000);
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const void* default_qnan_vector = getCurr();
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dd(0x7fc00000);
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dd(0x7fc00000);
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dd(0x7fc00000);
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dd(0x7fc00000);
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Xbyak::Label input_is_nan, input_is_zero, input_out_of_range;
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align(16);
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L(input_out_of_range);
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je(input_is_zero);
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movaps(SRC1, xword[rip + default_qnan_vector]);
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ret();
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L(input_is_zero);
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movaps(SRC1, xword[rip + negative_infinity_vector]);
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ret();
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align(16);
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L(subroutine);
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// Here we handle edge cases: input in {NaN, 0, -Inf, Negative}.
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xorps(SCRATCH, SCRATCH);
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ucomiss(SCRATCH, SRC1);
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jp(input_is_nan);
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jae(input_out_of_range);
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// Split input
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movd(eax, SRC1);
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mov(edx, eax);
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and_(eax, 0x7f800000);
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and_(edx, 0x007fffff);
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movss(SCRATCH, xword[rip + c0]); // Preload c0.
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or_(edx, 0x3f800000);
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movd(SRC1, edx);
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// SRC1 now contains the mantissa of the input.
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mulss(SCRATCH, SRC1);
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shr(eax, 23);
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sub(eax, 0x7f);
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cvtsi2ss(SCRATCH2, eax);
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// SCRATCH2 now contains the exponent of the input.
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// Complete computation of polynomial
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addss(SCRATCH, xword[rip + c1]);
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mulss(SCRATCH, SRC1);
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addss(SCRATCH, xword[rip + c2]);
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mulss(SCRATCH, SRC1);
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addss(SCRATCH, xword[rip + c3]);
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mulss(SCRATCH, SRC1);
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subss(SRC1, ONE);
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addss(SCRATCH, xword[rip + c4]);
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mulss(SCRATCH, SRC1);
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addss(SCRATCH2, SCRATCH);
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// Duplicate result across vector
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xorps(SRC1, SRC1); // break dependency chain
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movss(SRC1, SCRATCH2);
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L(input_is_nan);
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shufps(SRC1, SRC1, _MM_SHUFFLE(0, 0, 0, 0));
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ret();
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return subroutine;
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}
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Xbyak::Label JitShader::CompilePrelude_Exp2() {
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Xbyak::Label subroutine;
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// SSE does not have a exp instruction, thus we must approximate.
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// We perform this approximation first performaing a range reduction into the range [-0.5, 0.5).
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// A minimax polynomial which was fit for the function exp2(x) is then evaluated.
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// We then restore the result into the appropriate range.
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align(64);
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const void* input_max = getCurr();
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dd(0x43010000);
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const void* input_min = getCurr();
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dd(0xc2fdffff);
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const void* c0 = getCurr();
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dd(0x3c5dbe69);
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const void* half = getCurr();
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dd(0x3f000000);
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const void* c1 = getCurr();
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dd(0x3d5509f9);
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const void* c2 = getCurr();
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dd(0x3e773cc5);
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const void* c3 = getCurr();
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dd(0x3f3168b3);
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const void* c4 = getCurr();
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dd(0x3f800016);
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Xbyak::Label ret_label;
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align(16);
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L(subroutine);
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// Handle edge cases
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ucomiss(SRC1, SRC1);
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jp(ret_label);
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// Clamp to maximum range since we shift the value directly into the exponent.
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minss(SRC1, xword[rip + input_max]);
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maxss(SRC1, xword[rip + input_min]);
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// Decompose input
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movss(SCRATCH, SRC1);
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movss(SCRATCH2, xword[rip + c0]); // Preload c0.
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subss(SCRATCH, xword[rip + half]);
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cvtss2si(eax, SCRATCH);
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cvtsi2ss(SCRATCH, eax);
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// SCRATCH now contains input rounded to the nearest integer.
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add(eax, 0x7f);
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subss(SRC1, SCRATCH);
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// SRC1 contains input - round(input), which is in [-0.5, 0.5).
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mulss(SCRATCH2, SRC1);
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shl(eax, 23);
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movd(SCRATCH, eax);
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// SCRATCH contains 2^(round(input)).
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// Complete computation of polynomial.
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addss(SCRATCH2, xword[rip + c1]);
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mulss(SCRATCH2, SRC1);
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addss(SCRATCH2, xword[rip + c2]);
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mulss(SCRATCH2, SRC1);
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addss(SCRATCH2, xword[rip + c3]);
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mulss(SRC1, SCRATCH2);
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addss(SRC1, xword[rip + c4]);
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mulss(SRC1, SCRATCH);
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// Duplicate result across vector
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L(ret_label);
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shufps(SRC1, SRC1, _MM_SHUFFLE(0, 0, 0, 0));
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ret();
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return subroutine;
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}
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} // namespace Shader
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@ -106,6 +106,13 @@ private:
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*/
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void FindReturnOffsets();
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/**
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* Emits data and code for utility functions.
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*/
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void CompilePrelude();
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Xbyak::Label CompilePrelude_Log2();
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Xbyak::Label CompilePrelude_Exp2();
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const std::array<u32, MAX_PROGRAM_CODE_LENGTH>* program_code = nullptr;
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const std::array<u32, MAX_SWIZZLE_DATA_LENGTH>* swizzle_data = nullptr;
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@ -120,6 +127,9 @@ private:
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using CompiledShader = void(const void* setup, void* state, const u8* start_addr);
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CompiledShader* program = nullptr;
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Xbyak::Label log2_subroutine;
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Xbyak::Label exp2_subroutine;
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};
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} // Shader
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