1 files changed, 55 insertions, 10 deletions
diff --git a/src/shader_recompiler/backend/spirv/emit_spirv_image.cpp b/src/shader_recompiler/backend/spirv/emit_spirv_image.cpp
index fb5799c42..7d901c04b 100644
--- a/src/shader_recompiler/backend/spirv/emit_spirv_image.cpp
+++ b/src/shader_recompiler/backend/spirv/emit_spirv_image.cpp
@@ -201,6 +201,13 @@ Id Image(EmitContext& ctx, const IR::Value& index, IR::TextureInstInfo info) {
     }
 }
 
+bool IsTextureMsaa(EmitContext& ctx, const IR::TextureInstInfo& info) {
+    if (info.type == TextureType::Buffer) {
+        return false;
+    }
+    return ctx.textures.at(info.descriptor_index).is_multisample;
+}
+
 Id Decorate(EmitContext& ctx, IR::Inst* inst, Id sample) {
     const auto info{inst->Flags<IR::TextureInstInfo>()};
     if (info.relaxed_precision != 0) {
@@ -254,6 +261,30 @@ Id BitTest(EmitContext& ctx, Id mask, Id bit) {
     const Id bit_value{ctx.OpBitwiseAnd(ctx.U32[1], shifted, ctx.Const(1u))};
     return ctx.OpINotEqual(ctx.U1, bit_value, ctx.u32_zero_value);
 }
+
+Id ImageGatherSubpixelOffset(EmitContext& ctx, const IR::TextureInstInfo& info, Id texture,
+                             Id coords) {
+    // Apply a subpixel offset of 1/512 the texel size of the texture to ensure same rounding on
+    // AMD hardware as on Maxwell or other Nvidia architectures.
+    const auto calculate_coords{[&](size_t dim) {
+        const Id nudge{ctx.Const(0x1p-9f)};
+        const Id image_size{ctx.OpImageQuerySizeLod(ctx.U32[dim], texture, ctx.u32_zero_value)};
+        Id offset{dim == 2 ? ctx.ConstantComposite(ctx.F32[dim], nudge, nudge)
+                           : ctx.ConstantComposite(ctx.F32[dim], nudge, nudge, ctx.f32_zero_value)};
+        offset = ctx.OpFDiv(ctx.F32[dim], offset, ctx.OpConvertUToF(ctx.F32[dim], image_size));
+        return ctx.OpFAdd(ctx.F32[dim], coords, offset);
+    }};
+    switch (info.type) {
+    case TextureType::Color2D:
+    case TextureType::Color2DRect:
+        return calculate_coords(2);
+    case TextureType::ColorArray2D:
+    case TextureType::ColorCube:
+        return calculate_coords(3);
+    default:
+        return coords;
+    }
+}
 } // Anonymous namespace
 
 Id EmitBindlessImageSampleImplicitLod(EmitContext&) {
@@ -416,6 +447,9 @@ Id EmitImageGather(EmitContext& ctx, IR::Inst* inst, const IR::Value& index, Id
                    const IR::Value& offset, const IR::Value& offset2) {
     const auto info{inst->Flags<IR::TextureInstInfo>()};
     const ImageOperands operands(ctx, offset, offset2);
+    if (ctx.profile.need_gather_subpixel_offset) {
+        coords = ImageGatherSubpixelOffset(ctx, info, TextureImage(ctx, info, index), coords);
+    }
     return Emit(&EmitContext::OpImageSparseGather, &EmitContext::OpImageGather, ctx, inst,
                 ctx.F32[4], Texture(ctx, info, index), coords, ctx.Const(info.gather_component),
                 operands.MaskOptional(), operands.Span());
@@ -425,6 +459,9 @@ Id EmitImageGatherDref(EmitContext& ctx, IR::Inst* inst, const IR::Value& index,
                        const IR::Value& offset, const IR::Value& offset2, Id dref) {
     const auto info{inst->Flags<IR::TextureInstInfo>()};
     const ImageOperands operands(ctx, offset, offset2);
+    if (ctx.profile.need_gather_subpixel_offset) {
+        coords = ImageGatherSubpixelOffset(ctx, info, TextureImage(ctx, info, index), coords);
+    }
     return Emit(&EmitContext::OpImageSparseDrefGather, &EmitContext::OpImageDrefGather, ctx, inst,
                 ctx.F32[4], Texture(ctx, info, index), coords, dref, operands.MaskOptional(),
                 operands.Span());
@@ -436,34 +473,42 @@ Id EmitImageFetch(EmitContext& ctx, IR::Inst* inst, const IR::Value& index, Id c
     if (info.type == TextureType::Buffer) {
         lod = Id{};
     }
+    if (Sirit::ValidId(ms)) {
+        // This image is multisampled, lod must be implicit
+        lod = Id{};
+    }
     const ImageOperands operands(offset, lod, ms);
     return Emit(&EmitContext::OpImageSparseFetch, &EmitContext::OpImageFetch, ctx, inst, ctx.F32[4],
                 TextureImage(ctx, info, index), coords, operands.MaskOptional(), operands.Span());
 }
 
-Id EmitImageQueryDimensions(EmitContext& ctx, IR::Inst* inst, const IR::Value& index, Id lod) {
+Id EmitImageQueryDimensions(EmitContext& ctx, IR::Inst* inst, const IR::Value& index, Id lod,
+                            const IR::Value& skip_mips_val) {
     const auto info{inst->Flags<IR::TextureInstInfo>()};
     const Id image{TextureImage(ctx, info, index)};
     const Id zero{ctx.u32_zero_value};
-    const auto mips{[&] { return ctx.OpImageQueryLevels(ctx.U32[1], image); }};
+    const bool skip_mips{skip_mips_val.U1()};
+    const auto mips{[&] { return skip_mips ? zero : ctx.OpImageQueryLevels(ctx.U32[1], image); }};
+    const bool is_msaa{IsTextureMsaa(ctx, info)};
+    const bool uses_lod{!is_msaa && info.type != TextureType::Buffer};
+    const auto query{[&](Id type) {
+        return uses_lod ? ctx.OpImageQuerySizeLod(type, image, lod)
+                        : ctx.OpImageQuerySize(type, image);
+    }};
     switch (info.type) {
     case TextureType::Color1D:
-        return ctx.OpCompositeConstruct(ctx.U32[4], ctx.OpImageQuerySizeLod(ctx.U32[1], image, lod),
-                                        zero, zero, mips());
+        return ctx.OpCompositeConstruct(ctx.U32[4], query(ctx.U32[1]), zero, zero, mips());
     case TextureType::ColorArray1D:
     case TextureType::Color2D:
     case TextureType::ColorCube:
     case TextureType::Color2DRect:
-        return ctx.OpCompositeConstruct(ctx.U32[4], ctx.OpImageQuerySizeLod(ctx.U32[2], image, lod),
-                                        zero, mips());
+        return ctx.OpCompositeConstruct(ctx.U32[4], query(ctx.U32[2]), zero, mips());
     case TextureType::ColorArray2D:
     case TextureType::Color3D:
     case TextureType::ColorArrayCube:
-        return ctx.OpCompositeConstruct(ctx.U32[4], ctx.OpImageQuerySizeLod(ctx.U32[3], image, lod),
-                                        mips());
+        return ctx.OpCompositeConstruct(ctx.U32[4], query(ctx.U32[3]), mips());
     case TextureType::Buffer:
-        return ctx.OpCompositeConstruct(ctx.U32[4], ctx.OpImageQuerySize(ctx.U32[1], image), zero,
-                                        zero, mips());
+        return ctx.OpCompositeConstruct(ctx.U32[4], query(ctx.U32[1]), zero, zero, mips());
     }
     throw LogicError("Unspecified image type {}", info.type.Value());
 }