From 976cb0e21a7dec78a15920f4fa6e12e6975ce449 Mon Sep 17 00:00:00 2001
From: baldurk <baldurk@baldurk.org>
Date: Mon, 6 Sep 2021 17:07:35 +0100
Subject: [PATCH] Preserve uselists through DXIL decode/encode

---
 .../driver/shaders/dxil/dxil_bytecode.cpp     | 25 ++++++++++++++++++-
 renderdoc/driver/shaders/dxil/dxil_bytecode.h |  9 +++++++
 .../shaders/dxil/dxil_bytecode_editor.cpp     | 15 +++++++++++
 renderdoc/driver/shaders/dxil/llvm_common.h   |  6 +++++
 4 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/renderdoc/driver/shaders/dxil/dxil_bytecode.cpp b/renderdoc/driver/shaders/dxil/dxil_bytecode.cpp
index dcce8c0cb..4086490fd 100644
--- a/renderdoc/driver/shaders/dxil/dxil_bytecode.cpp
+++ b/renderdoc/driver/shaders/dxil/dxil_bytecode.cpp
@@ -1149,7 +1149,30 @@ Program::Program(const byte *bytes, size_t length)
             }
             else if(IS_KNOWN(funcChild.id, KnownBlock::USELIST_BLOCK))
             {
-              RDCDEBUG("Ignoring uselist block");
+              for(const LLVMBC::BlockOrRecord &uselist : funcChild.children)
+              {
+                if(uselist.IsBlock())
+                {
+                  RDCERR("Unexpected subblock in USELIST_BLOCK");
+                  continue;
+                }
+
+                const bool bb = IS_KNOWN(uselist.id, UselistRecord::BB);
+                if(IS_KNOWN(uselist.id, UselistRecord::DEFAULT) || bb)
+                {
+                  UselistEntry u;
+                  u.block = bb;
+                  u.shuffle = uselist.ops;
+                  u.value = m_Values[(size_t)u.shuffle.back()];
+                  u.shuffle.pop_back();
+                  f.uselist.push_back(u);
+                }
+                else
+                {
+                  RDCERR("Unexpected record %u in USELIST_BLOCK", uselist.id);
+                  continue;
+                }
+              }
             }
             else
             {
diff --git a/renderdoc/driver/shaders/dxil/dxil_bytecode.h b/renderdoc/driver/shaders/dxil/dxil_bytecode.h
index bd6afe944..c1bdc9d6f 100644
--- a/renderdoc/driver/shaders/dxil/dxil_bytecode.h
+++ b/renderdoc/driver/shaders/dxil/dxil_bytecode.h
@@ -579,6 +579,13 @@ struct Block
   rdcarray<const Block *> preds;
 };
 
+struct UselistEntry
+{
+  bool block = false;
+  Value value;
+  rdcarray<uint64_t> shuffle;
+};
+
 struct Function
 {
   rdcstr name;
@@ -597,6 +604,8 @@ struct Function
   rdcarray<Constant> constants;
   rdcarray<Metadata> metadata;
 
+  rdcarray<UselistEntry> uselist;
+
   AttachedMetadata attachedMeta;
 };
 
diff --git a/renderdoc/driver/shaders/dxil/dxil_bytecode_editor.cpp b/renderdoc/driver/shaders/dxil/dxil_bytecode_editor.cpp
index d15480d77..626006983 100644
--- a/renderdoc/driver/shaders/dxil/dxil_bytecode_editor.cpp
+++ b/renderdoc/driver/shaders/dxil/dxil_bytecode_editor.cpp
@@ -1098,6 +1098,21 @@ bytebuf DXIL::ProgramEditor::EncodeProgram() const
       writer.EndBlock();
     }
 
+    if(!f.uselist.empty())
+    {
+      writer.BeginBlock(LLVMBC::KnownBlock::USELIST_BLOCK);
+
+      for(const UselistEntry &u : f.uselist)
+      {
+        vals = u.shuffle;
+        vals.push_back(getValueID(u.value));
+
+        writer.Record(u.block ? LLVMBC::UselistRecord::BB : LLVMBC::UselistRecord::DEFAULT, vals);
+      }
+
+      writer.EndBlock();
+    }
+
     writer.EndBlock();
 
     values.resize(values.size() - f.values.size());
diff --git a/renderdoc/driver/shaders/dxil/llvm_common.h b/renderdoc/driver/shaders/dxil/llvm_common.h
index c5ce00fcd..f6172e1f2 100644
--- a/renderdoc/driver/shaders/dxil/llvm_common.h
+++ b/renderdoc/driver/shaders/dxil/llvm_common.h
@@ -175,6 +175,12 @@ enum class ValueSymtabRecord : uint32_t
   COMBINED_ENTRY = 5,
 };
 
+enum class UselistRecord : uint32_t
+{
+  DEFAULT = 1,
+  BB = 2,
+};
+
 enum class MetaDataRecord : uint32_t
 {
   STRING_OLD = 1,