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 5867a04aba..32c4f1da21 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 40f4535938..2892074e11 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<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) {