From 27ca8a0e13deeebb4185ec22619d2b78b5ad8b21 Mon Sep 17 00:00:00 2001 From: ameerj <52414509+ameerj@users.noreply.github.com> Date: Tue, 22 Jun 2021 23:09:22 -0400 Subject: [PATCH] glsl: Better IAdd Overflow CC fix This ensures the original operand values are not overwritten when being used in the overflow detection. --- .../backend/glsl/emit_glsl.cpp | 2 +- .../backend/glsl/emit_glsl_integer.cpp | 22 ++++++++++--------- 2 files changed, 13 insertions(+), 11 deletions(-) diff --git a/src/shader_recompiler/backend/glsl/emit_glsl.cpp b/src/shader_recompiler/backend/glsl/emit_glsl.cpp index 5867a04ab..32c4f1da2 100644 --- a/src/shader_recompiler/backend/glsl/emit_glsl.cpp +++ b/src/shader_recompiler/backend/glsl/emit_glsl.cpp @@ -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;"; diff --git a/src/shader_recompiler/backend/glsl/emit_glsl_integer.cpp b/src/shader_recompiler/backend/glsl/emit_glsl_integer.cpp index 40f453593..2892074e1 100644 --- a/src/shader_recompiler/backend/glsl/emit_glsl_integer.cpp +++ b/src/shader_recompiler/backend/glsl/emit_glsl_integer.cpp @@ -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(std::numeric_limits::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({})=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(std::numeric_limits::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({})Invalidate(); - } } void EmitIAdd64(EmitContext& ctx, IR::Inst& inst, std::string_view a, std::string_view b) {