[spirv] Add 'late' constants

Late constants can be used to reserve a placeholder ID for a constant
before the constant's value is known. The value can be changed later.
Only scalar 32-bit integer and floating point types are supported
as of right now.

src/spirv/spirv_module.cpp

@@ -361,6 +361,38 @@ namespace dxvk {
   }
 
 
+  uint32_t SpirvModule::lateConst32(
+          uint32_t                typeId) {
+    uint32_t resultId = this->allocateId();
+    m_lateConsts.insert(resultId);
+
+    m_typeConstDefs.putIns (spv::OpConstant, 4);
+    m_typeConstDefs.putWord(typeId);
+    m_typeConstDefs.putWord(resultId);
+    m_typeConstDefs.putWord(0);
+    return resultId;
+  }
+
+
+  void SpirvModule::setLateConst(
+            uint32_t                constId,
+      const uint32_t*               argIds) {
+    for (auto ins : m_typeConstDefs) {
+      if (ins.opCode() != spv::OpConstant
+       && ins.opCode() != spv::OpConstantComposite)
+        continue;
+      
+      if (ins.arg(2) != constId)
+        continue;
+
+      for (uint32_t i = 3; i < ins.length(); i++)
+        ins.setArg(i, argIds[i - 3]);
+
+      return;
+    }
+  }
+
+
   uint32_t SpirvModule::specConstBool(
           bool                    v) {
     uint32_t typeId   = this->defBoolType();
@@ -3371,8 +3403,13 @@ namespace dxvk {
       for (uint32_t i = 0; i < argCount && match; i++)
         match &= ins.arg(3 + i) == argIds[i];
       
-      if (match)
-        return ins.arg(2);
+      if (!match)
+        continue;
+      
+      uint32_t id = ins.arg(2);
+
+      if (m_lateConsts.find(id) == m_lateConsts.end())
+        return id;
     }
     
     // Constant not yet declared, make a new one

src/spirv/spirv_module.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <unordered_set>
+
 #include "spirv_code_buffer.h"
 
 namespace dxvk {
@@ -167,6 +169,13 @@ namespace dxvk {
     uint32_t constUndef(
             uint32_t                typeId);
     
+    uint32_t lateConst32(
+            uint32_t                typeId);
+
+    void setLateConst(
+            uint32_t                constId,
+      const uint32_t*               argIds);
+
     uint32_t specConstBool(
             bool                    v);
     
@@ -1166,6 +1175,8 @@ namespace dxvk {
     SpirvCodeBuffer m_typeConstDefs;
     SpirvCodeBuffer m_variables;
     SpirvCodeBuffer m_code;
+
+    std::unordered_set<uint32_t> m_lateConsts;
     
     uint32_t defType(
             spv::Op                 op,