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[DXBC] Multiplication signed zero handling

This commit is contained in:
Triang3l 2020-10-30 22:14:38 +03:00
parent adebaba799
commit feb8258a5e
3 changed files with 124 additions and 144 deletions
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215
src/xenia/gpu/dxbc_shader_translator_alu.cc
View File

@ -68,32 +68,34 @@ void DxbcShaderTranslator::ProcessVectorAluOperation(
break;
case AluVectorOpcode::kMul:
case AluVectorOpcode::kMad: {
bool is_mad = instr.vector_opcode == AluVectorOpcode::kMad;
if (is_mad) {
DxbcOpMAd(per_component_dest, operands[0], operands[1], operands[2]);
} else {
DxbcOpMul(per_component_dest, operands[0], operands[1]);
}
// Shader Model 3: 0 or denormal * anything = 0.
// FIXME(Triang3l): Signed zero needs research and handling.
uint32_t absolute_different =
// Not using DXBC mad to prevent fused multiply-add (mul followed by add
// may be optimized into non-fused mad by the driver in the identical
// operands case also).
DxbcOpMul(per_component_dest, operands[0], operands[1]);
uint32_t multiplicands_different =
used_result_components &
~instr.vector_operands[0].GetAbsoluteIdenticalComponents(
~instr.vector_operands[0].GetIdenticalMultiplicandComponents(
instr.vector_operands[1]);
if (absolute_different) {
if (multiplicands_different) {
// Shader Model 3: +-0 or denormal * anything = +0.
uint32_t is_zero_temp = PushSystemTemp();
DxbcOpMin(DxbcDest::R(is_zero_temp, absolute_different),
DxbcOpMin(DxbcDest::R(is_zero_temp, multiplicands_different),
operands[0].Abs(), operands[1].Abs());
// min isn't required to flush denormals, eq is.
DxbcOpEq(DxbcDest::R(is_zero_temp, absolute_different),
DxbcOpEq(DxbcDest::R(is_zero_temp, multiplicands_different),
DxbcSrc::R(is_zero_temp), DxbcSrc::LF(0.0f));
DxbcOpMovC(DxbcDest::R(system_temp_result_, absolute_different),
DxbcSrc::R(is_zero_temp),
is_mad ? operands[2] : DxbcSrc::LF(0.0f),
// Not replacing true `0 + term` with movc of the term because +0 + -0
// should result in +0, not -0.
DxbcOpMovC(DxbcDest::R(system_temp_result_, multiplicands_different),
DxbcSrc::R(is_zero_temp), DxbcSrc::LF(0.0f),
DxbcSrc::R(system_temp_result_));
// Release is_zero_temp.
PopSystemTemp();
}
if (instr.vector_opcode == AluVectorOpcode::kMad) {
DxbcOpAdd(per_component_dest, DxbcSrc::R(system_temp_result_),
operands[2]);
}
} break;
case AluVectorOpcode::kMax:
@ -179,69 +181,41 @@ void DxbcShaderTranslator::ProcessVectorAluOperation(
component_count = 4;
}
result_swizzle = DxbcSrc::kXXXX;
uint32_t absolute_different =
uint32_t multiplicands_different =
uint32_t((1 << component_count) - 1) &
~instr.vector_operands[0].GetAbsoluteIdenticalComponents(
~instr.vector_operands[0].GetIdenticalMultiplicandComponents(
instr.vector_operands[1]);
if (absolute_different) {
// Shader Model 3: 0 or denormal * anything = 0.
// FIXME(Triang3l): Signed zero needs research and handling.
// Add component products only if non-zero. For dp4, 16 scalar
// operations in the worst case (as opposed to always 20 for
// eq/movc/eq/movc/dp4 or min/eq/movc/movc/dp4 for preparing operands
// for dp4).
DxbcOpMul(DxbcDest::R(system_temp_result_, 0b0001),
operands[0].SelectFromSwizzled(0),
operands[1].SelectFromSwizzled(0));
if (absolute_different & 0b0001) {
DxbcOpMin(DxbcDest::R(system_temp_result_, 0b0010),
operands[0].SelectFromSwizzled(0).Abs(),
operands[1].SelectFromSwizzled(0).Abs());
DxbcOpEq(DxbcDest::R(system_temp_result_, 0b0010),
DxbcSrc::R(system_temp_result_, DxbcSrc::kYYYY),
for (uint32_t i = 0; i < component_count; ++i) {
DxbcOpMul(DxbcDest::R(system_temp_result_, i ? 0b0010 : 0b0001),
operands[0].SelectFromSwizzled(i),
operands[1].SelectFromSwizzled(i));
if ((multiplicands_different & (1 << i)) != 0) {
// Shader Model 3: +-0 or denormal * anything = +0 (also not replacing
// true `0 + term` with movc of the term because +0 + -0 should result
// in +0, not -0).
DxbcOpMin(DxbcDest::R(system_temp_result_, 0b0100),
operands[0].SelectFromSwizzled(i).Abs(),
operands[1].SelectFromSwizzled(i).Abs());
DxbcOpEq(DxbcDest::R(system_temp_result_, 0b0100),
DxbcSrc::R(system_temp_result_, DxbcSrc::kZZZZ),
DxbcSrc::LF(0.0f));
DxbcOpMovC(DxbcDest::R(system_temp_result_, 0b0001),
DxbcSrc::R(system_temp_result_, DxbcSrc::kYYYY),
DxbcSrc::LF(0.0f),
DxbcSrc::R(system_temp_result_, DxbcSrc::kXXXX));
}
for (uint32_t i = 1; i < component_count; ++i) {
bool component_different = (absolute_different & (1 << i)) != 0;
DxbcOpMAd(DxbcDest::R(system_temp_result_,
component_different ? 0b0010 : 0b0001),
operands[0].SelectFromSwizzled(i),
operands[1].SelectFromSwizzled(i),
DxbcSrc::R(system_temp_result_, DxbcSrc::kXXXX));
if (component_different) {
DxbcOpMin(DxbcDest::R(system_temp_result_, 0b0100),
operands[0].SelectFromSwizzled(i).Abs(),
operands[1].SelectFromSwizzled(i).Abs());
DxbcOpEq(DxbcDest::R(system_temp_result_, 0b0100),
DxbcOpMovC(DxbcDest::R(system_temp_result_, i ? 0b0010 : 0b0001),
DxbcSrc::R(system_temp_result_, DxbcSrc::kZZZZ),
DxbcSrc::LF(0.0f));
DxbcOpMovC(DxbcDest::R(system_temp_result_, 0b0001),
DxbcSrc::R(system_temp_result_, DxbcSrc::kZZZZ),
DxbcSrc::R(system_temp_result_, DxbcSrc::kXXXX),
DxbcSrc::R(system_temp_result_, DxbcSrc::kYYYY));
}
DxbcSrc::LF(0.0f),
DxbcSrc::R(system_temp_result_,
i ? DxbcSrc::kYYYY : DxbcSrc::kXXXX));
}
} else {
if (component_count == 2) {
DxbcOpDP2(DxbcDest::R(system_temp_result_, 0b0001), operands[0],
operands[1]);
} else if (component_count == 3) {
DxbcOpDP3(DxbcDest::R(system_temp_result_, 0b0001), operands[0],
operands[1]);
} else {
assert_true(component_count == 4);
DxbcOpDP4(DxbcDest::R(system_temp_result_, 0b0001), operands[0],
operands[1]);
if (i) {
// Not using DXBC dp# to avoid fused multiply-add, PC GPUs are scalar
// as of 2020 anyway, and not using mad for the same reason (mul
// followed by add may be optimized into non-fused mad by the driver
// in the identical operands case also).
DxbcOpAdd(DxbcDest::R(system_temp_result_, 0b0001),
DxbcSrc::R(system_temp_result_, DxbcSrc::kXXXX),
DxbcSrc::R(system_temp_result_, DxbcSrc::kYYYY));
}
}
if (component_count == 2) {
// Add the third operand. Since floating-point addition isn't
// associative, even though adding this in multiply-add for the first
// component would be faster, it's safer to add here, in the end.
DxbcOpAdd(DxbcDest::R(system_temp_result_, 0b0001),
DxbcSrc::R(system_temp_result_, DxbcSrc::kXXXX),
operands[2].SelectFromSwizzled(0));
@ -592,14 +566,13 @@ void DxbcShaderTranslator::ProcessVectorAluOperation(
DxbcOpMov(DxbcDest::R(system_temp_result_, 0b0001), DxbcSrc::LF(1.0f));
}
if (used_result_components & 0b0010) {
// Shader Model 3: 0 or denormal * anything = 0.
// FIXME(Triang3l): Signed zero needs research and handling.
DxbcOpMul(DxbcDest::R(system_temp_result_, 0b0010),
operands[0].SelectFromSwizzled(1),
operands[1].SelectFromSwizzled(1));
if (!(instr.vector_operands[0].GetAbsoluteIdenticalComponents(
if (!(instr.vector_operands[0].GetIdenticalMultiplicandComponents(
instr.vector_operands[1]) &
0b0010)) {
// Shader Model 3: +-0 or denormal * anything = +0.
DxbcOpMin(DxbcDest::R(system_temp_result_, 0b0100),
operands[0].SelectFromSwizzled(1).Abs(),
operands[1].SelectFromSwizzled(1).Abs());
@ -700,8 +673,7 @@ void DxbcShaderTranslator::ProcessScalarAluOperation(
DxbcOpMul(ps_dest, operand_0_a, operand_0_b);
if (instr.scalar_operands[0].components[0] !=
instr.scalar_operands[0].components[1]) {
// Shader Model 3: 0 or denormal * anything = 0.
// FIXME(Triang3l): Signed zero needs research and handling.
// Shader Model 3: +-0 or denormal * anything = +0.
uint32_t is_zero_temp = PushSystemTemp();
DxbcOpMin(DxbcDest::R(is_zero_temp, 0b0001), operand_0_a.Abs(),
operand_0_b.Abs());
@ -714,58 +686,50 @@ void DxbcShaderTranslator::ProcessScalarAluOperation(
PopSystemTemp();
}
break;
case AluScalarOpcode::kMulsPrev: {
// Shader Model 3: 0 or denormal * anything = 0.
// FIXME(Triang3l): Signed zero needs research and handling.
uint32_t is_zero_temp = PushSystemTemp();
DxbcOpMin(DxbcDest::R(is_zero_temp, 0b0001), operand_0_a.Abs(),
ps_src.Abs());
// min isn't required to flush denormals, eq is.
DxbcOpEq(DxbcDest::R(is_zero_temp, 0b0001),
DxbcSrc::R(is_zero_temp, DxbcSrc::kXXXX), DxbcSrc::LF(0.0f));
DxbcOpMul(ps_dest, operand_0_a, ps_src);
DxbcOpMovC(ps_dest, DxbcSrc::R(is_zero_temp, DxbcSrc::kXXXX),
DxbcSrc::LF(0.0f), ps_src);
// Release is_zero_temp.
PopSystemTemp();
} break;
case AluScalarOpcode::kMulsPrev:
case AluScalarOpcode::kMulsPrev2: {
uint32_t test_temp = PushSystemTemp();
// Check if need to select the src0.a * ps case.
// ps != -FLT_MAX.
DxbcOpNE(DxbcDest::R(test_temp, 0b0001), ps_src, DxbcSrc::LF(-FLT_MAX));
// isfinite(ps), or |ps| <= FLT_MAX, or -|ps| >= -FLT_MAX, since -FLT_MAX
// is already loaded to an SGPR, this is also false if it's NaN.
DxbcOpGE(DxbcDest::R(test_temp, 0b0010), -ps_src.Abs(),
DxbcSrc::LF(-FLT_MAX));
DxbcOpAnd(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::R(test_temp, DxbcSrc::kYYYY));
// isfinite(src0.b).
DxbcOpGE(DxbcDest::R(test_temp, 0b0010), -operand_0_b.Abs(),
DxbcSrc::LF(-FLT_MAX));
DxbcOpAnd(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::R(test_temp, DxbcSrc::kYYYY));
// src0.b > 0 (need !(src0.b <= 0), but src0.b has already been checked
// for NaN).
DxbcOpLT(DxbcDest::R(test_temp, 0b0010), DxbcSrc::LF(0.0f), operand_0_b);
DxbcOpAnd(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::R(test_temp, DxbcSrc::kYYYY));
DxbcOpIf(true, DxbcSrc::R(test_temp, DxbcSrc::kXXXX));
// Shader Model 3: 0 or denormal * anything = 0.
// ps is already known to be not NaN or Infinity, so multiplying it by 0
// will result in 0. However, src0.a can be anything, so the result should
// be zero if ps is zero.
// FIXME(Triang3l): Signed zero needs research and handling.
DxbcOpEq(DxbcDest::R(test_temp, 0b0001), ps_src, DxbcSrc::LF(0.0f));
if (instr.scalar_opcode == AluScalarOpcode::kMulsPrev2) {
// Check if need to select the src0.a * ps case.
// ps != -FLT_MAX.
DxbcOpNE(DxbcDest::R(test_temp, 0b0001), ps_src, DxbcSrc::LF(-FLT_MAX));
// isfinite(ps), or |ps| <= FLT_MAX, or -|ps| >= -FLT_MAX, since
// -FLT_MAX is already loaded to an SGPR, this is also false if it's
// NaN.
DxbcOpGE(DxbcDest::R(test_temp, 0b0010), -ps_src.Abs(),
DxbcSrc::LF(-FLT_MAX));
DxbcOpAnd(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::R(test_temp, DxbcSrc::kYYYY));
// isfinite(src0.b).
DxbcOpGE(DxbcDest::R(test_temp, 0b0010), -operand_0_b.Abs(),
DxbcSrc::LF(-FLT_MAX));
DxbcOpAnd(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::R(test_temp, DxbcSrc::kYYYY));
// src0.b > 0 (need !(src0.b <= 0), but src0.b has already been checked
// for NaN).
DxbcOpLT(DxbcDest::R(test_temp, 0b0010), DxbcSrc::LF(0.0f),
operand_0_b);
DxbcOpAnd(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::R(test_temp, DxbcSrc::kYYYY));
DxbcOpIf(true, DxbcSrc::R(test_temp, DxbcSrc::kXXXX));
}
// Shader Model 3: +-0 or denormal * anything = +0.
DxbcOpMin(DxbcDest::R(test_temp, 0b0001), operand_0_a.Abs(),
ps_src.Abs());
// min isn't required to flush denormals, eq is.
DxbcOpEq(DxbcDest::R(test_temp, 0b0001),
DxbcSrc::R(test_temp, DxbcSrc::kXXXX), DxbcSrc::LF(0.0f));
DxbcOpMul(ps_dest, operand_0_a, ps_src);
DxbcOpMovC(ps_dest, DxbcSrc::R(test_temp, DxbcSrc::kXXXX),
DxbcSrc::LF(0.0f), ps_src);
DxbcOpElse();
DxbcOpMov(ps_dest, DxbcSrc::LF(-FLT_MAX));
DxbcOpEndIf();
if (instr.scalar_opcode == AluScalarOpcode::kMulsPrev2) {
DxbcOpElse();
DxbcOpMov(ps_dest, DxbcSrc::LF(-FLT_MAX));
DxbcOpEndIf();
}
// Release test_temp.
PopSystemTemp();
} break;
@ -1023,11 +987,10 @@ void DxbcShaderTranslator::ProcessScalarAluOperation(
case AluScalarOpcode::kMulsc0:
case AluScalarOpcode::kMulsc1:
DxbcOpMul(ps_dest, operand_0_a, operand_1);
if (!(instr.scalar_operands[0].GetAbsoluteIdenticalComponents(
if (!(instr.scalar_operands[0].GetIdenticalMultiplicandComponents(
instr.scalar_operands[1]) &
0b0001)) {
// Shader Model 3: 0 or denormal * anything = 0.
// FIXME(Triang3l): Signed zero needs research and handling.
// Shader Model 3: +-0 or denormal * anything = +0.
uint32_t is_zero_temp = PushSystemTemp();
DxbcOpMin(DxbcDest::R(is_zero_temp, 0b0001), operand_0_a.Abs(),
operand_1.Abs());

26
src/xenia/gpu/shader.h
View File

@ -212,14 +212,19 @@ struct InstructionOperand {
return false;
}
// Returns which components of two operands are identical, but may have
// different signs (for simplicity of usage with GetComponent, treating the
// rightmost component as replicated).
uint32_t GetAbsoluteIdenticalComponents(
// Returns which components of two operands are identical, so that
// multiplication of them would result in pow2 with + sign, including in case
// they're zero (because -0 * |-0|, or -0 * +0, is -0), for providing a fast
// path in emulation of the Shader Model 3 +-0 * x = +0 multiplication
// behavior (disregarding component_count for simplicity of usage with
// GetComponent, treating the rightmost component as replicated).
uint32_t GetIdenticalMultiplicandComponents(
const InstructionOperand& other) const {
if (storage_source != other.storage_source ||
storage_index != other.storage_index ||
storage_addressing_mode != other.storage_addressing_mode) {
storage_addressing_mode != other.storage_addressing_mode ||
is_absolute_value != other.is_absolute_value ||
(!is_absolute_value && is_negated != other.is_negated)) {
return 0;
}
uint32_t identical_components = 0;
@ -229,15 +234,14 @@ struct InstructionOperand {
}
return identical_components;
}
// Returns which components of two operands will always be bitwise equal, but
// may have different signs (disregarding component_count for simplicity of
// usage with GetComponent, treating the rightmost component as replicated).
// Returns which components of two operands will always be bitwise equal
// (disregarding component_count for simplicity of usage with GetComponent,
// treating the rightmost component as replicated).
uint32_t GetIdenticalComponents(const InstructionOperand& other) const {
if (is_negated != other.is_negated ||
is_absolute_value != other.is_absolute_value) {
if (is_negated != other.is_negated) {
return 0;
}
return GetAbsoluteIdenticalComponents(other);
return GetIdenticalMultiplicandComponents(other);
}
};

27
src/xenia/gpu/ucode.h
View File

@ -800,13 +800,26 @@ static_assert_size(TextureFetchInstruction, 12);
// Both are valid only within the current ALU clause. They are not modified
// when the instruction that would write them fails its predication check.
// - Direct3D 9 rules (like in GCN v_*_legacy_f32 instructions) for
// multiplication (0 or denormal * anything = 0) wherever it's present (mul,
// mad, dp, etc.) and for NaN in min/max. It's very important to respect this
// rule for multiplication, as games often rely on it in vector normalization
// (rcp and mul), Infinity * 0 resulting in NaN breaks a lot of things in
// games - causes white screen in Halo 3, white specular on characters in GTA
// IV.
// TODO(Triang3l): Investigate signed zero handling in multiplication.
// multiplication (+-0 or denormal * anything = +0) wherever it's present
// (mul, mad, dp, etc.) and for NaN in min/max. It's very important to respect
// this rule for multiplication, as games often rely on it in vector
// normalization (rcp and mul), Infinity * 0 resulting in NaN breaks a lot of
// things in games - causes white screen in Halo 3, white specular on
// characters in GTA IV. The result is always positive zero in this case, no
// matter what the signs of the other operands are, according to R5xx
// Acceleration section 8.7.5 "Legacy multiply behavior" and testing on
// Adreno 200. This means that the following need to be taken into account
// (according to 8.7.2 "ALU Non-Transcendental Floating Point"):
// - +0 * -0 is -0 with IEEE conformance, however, with this legacy SM3
// handling, it should result in +0.
// - +0 + -0 is +0, so multiply-add should not be replaced with conditional
// move of the third operand in case of zero multiplicands, because the term
// may be -0, while the result should be +0 in this case.
// http://developer.amd.com/wordpress/media/2013/10/R5xx_Acceleration_v1.5.pdf
// Multiply-add also appears to be not fused (the SM3 behavior instruction on
// GCN is called v_mad_legacy_f32, not v_fma_legacy_f32) - shader translators
// should not use instructions that may be interpreted by the host GPU as
// fused multiply-add.
enum class AluScalarOpcode : uint32_t {
// Floating-Point Add