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glsl: Better IAdd Overflow CC fix

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This ensures the original operand values are not overwritten when being used in the overflow detection.
This commit is contained in:
ameerj 2021-06-22 23:09:22 -04:00
parent 4397053d5c
commit 27ca8a0e13
2 changed files with 13 additions and 11 deletions
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2
src/shader_recompiler/backend/glsl/emit_glsl.cpp
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@ -227,7 +227,7 @@ std::string EmitGLSL(const Profile& profile, const RuntimeInfo& runtime_info, IR
ctx.header += "void main(){\n";
DefineVariables(ctx, ctx.header);
if (ctx.uses_cc_carry) {
ctx.header += "uint carry;uint iadd_op_b;";
ctx.header += "uint carry;";
}
if (program.info.uses_subgroup_shuffles) {
ctx.header += "bool shfl_in_bounds;";

22
src/shader_recompiler/backend/glsl/emit_glsl_integer.cpp
View file

@ -30,10 +30,21 @@ void SetSignFlag(EmitContext& ctx, IR::Inst& inst, std::string_view result) {
} // Anonymous namespace
void EmitIAdd32(EmitContext& ctx, IR::Inst& inst, std::string_view a, std::string_view b) {
// Compute the overflow CC first as it requires the original operand values,
// which may be overwritten by the result of the addition
if (IR::Inst * overflow{inst.GetAssociatedPseudoOperation(IR::Opcode::GetOverflowFromOp)}) {
// https://stackoverflow.com/questions/55468823/how-to-detect-integer-overflow-in-c
constexpr u32 s32_max{static_cast<u32>(std::numeric_limits<s32>::max())};
const auto sub_a{fmt::format("{}u-{}", s32_max, a)};
const auto positive_result{fmt::format("int({})>int({})", b, sub_a)};
const auto negative_result{fmt::format("int({})<int({})", b, sub_a)};
ctx.AddU1("{}=int({})>=0?{}:{};", *overflow, a, positive_result, negative_result);
overflow->Invalidate();
}
const auto result{ctx.var_alloc.Define(inst, GlslVarType::U32)};
if (IR::Inst* const carry{inst.GetAssociatedPseudoOperation(IR::Opcode::GetCarryFromOp)}) {
ctx.uses_cc_carry = true;
ctx.Add("iadd_op_b={};{}=uaddCarry({},{},carry);", b, result, a, b);
ctx.Add("{}=uaddCarry({},{},carry);", result, a, b);
ctx.AddU1("{}=carry!=0;", *carry);
carry->Invalidate();
} else {
@ -41,15 +52,6 @@ void EmitIAdd32(EmitContext& ctx, IR::Inst& inst, std::string_view a, std::strin
}
SetZeroFlag(ctx, inst, result);
SetSignFlag(ctx, inst, result);
if (IR::Inst * overflow{inst.GetAssociatedPseudoOperation(IR::Opcode::GetOverflowFromOp)}) {
// https://stackoverflow.com/questions/55468823/how-to-detect-integer-overflow-in-c
constexpr u32 s32_max{static_cast<u32>(std::numeric_limits<s32>::max())};
const auto sub_a{fmt::format("{}u-{}", s32_max, a)};
const auto op_b{ctx.uses_cc_carry ? "iadd_op_b" : b};
ctx.AddU1("{}=int({})>=0?int({})>int({}):int({})<int({});", *overflow, a, op_b, sub_a, op_b,
sub_a);
overflow->Invalidate();
}
}
void EmitIAdd64(EmitContext& ctx, IR::Inst& inst, std::string_view a, std::string_view b) {