Add option to preserve shader parameter declaration in output SPIRV. (#4344)

* Add option to preserve shader parameter declarations in output.

* Add test.

12 files changed, 49 insertions, 15 deletions

diff --git a/docs/command-line-slangc-reference.md b/docs/command-line-slangc-reference.md
index 7c2beb7e0..594e25912 100644
--- a/docs/command-line-slangc-reference.md
+++ b/docs/command-line-slangc-reference.md
diff --git a/slang.h b/slang.h
index ce659b007..d807efec4 100644
--- a/slang.h
+++ b/slang.h
@@ -865,6 +865,7 @@ extern "C"
             MinimumSlangOptimization, // bool
             DisableNonEssentialValidations, // bool
             DisableSourceMap,       // bool
+            PreserveParameters,       // bool: preserve all resource parameters in the output code.
 
             // Target
 
diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index fd4b1d491..10c263793 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -6431,10 +6431,13 @@ SlangResult emitSPIRVFromIR(
     }
 #endif
 
+    auto shouldPreserveParams = codeGenContext->getTargetProgram()->getOptionSet().getBoolOption(CompilerOptionName::PreserveParameters);
     for (auto inst : irModule->getGlobalInsts())
     {
         if (as<IRDebugSource>(inst))
             context.ensureInst(inst);
+        if (shouldPreserveParams && as<IRGlobalParam>(inst))
+            context.ensureInst(inst);
     }
 
     // Emit source language info.
diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index 6d0ab1daa..38f066c6c 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -585,6 +585,7 @@ Result linkAndOptimizeIR(
     IRDeadCodeEliminationOptions deadCodeEliminationOptions = IRDeadCodeEliminationOptions();
     fastIRSimplificationOptions.minimalOptimization = defaultIRSimplificationOptions.minimalOptimization;
     deadCodeEliminationOptions.useFastAnalysis = fastIRSimplificationOptions.minimalOptimization;
+    deadCodeEliminationOptions.keepGlobalParamsAlive = targetProgram->getOptionSet().getBoolOption(CompilerOptionName::PreserveParameters);
 
     simplifyIR(targetProgram, irModule, defaultIRSimplificationOptions, sink);
 
diff --git a/source/slang/slang-ir-dce.cpp b/source/slang/slang-ir-dce.cpp
index 4eefeabd5..f414f7266 100644
--- a/source/slang/slang-ir-dce.cpp
+++ b/source/slang/slang-ir-dce.cpp
@@ -423,6 +423,8 @@ bool shouldInstBeLiveIfParentIsLive(IRInst* inst, IRDeadCodeEliminationOptions o
     case kIROp_WitnessTableEntry:
         return true;
 
+    case kIROp_GlobalParam:
+        return options.keepGlobalParamsAlive;
     default:
         break;
     }
diff --git a/source/slang/slang-ir-dce.h b/source/slang/slang-ir-dce.h
index d52ec817e..55eed1c92 100644
--- a/source/slang/slang-ir-dce.h
+++ b/source/slang/slang-ir-dce.h
@@ -12,6 +12,7 @@ namespace Slang
         bool keepExportsAlive = false;
         bool keepLayoutsAlive = false;
         bool useFastAnalysis = false;
+        bool keepGlobalParamsAlive = true;
     };
 
         /// Eliminate "dead" code from the given IR module.
diff --git a/source/slang/slang-ir-link.cpp b/source/slang/slang-ir-link.cpp
index eb660c8a7..5bb485b22 100644
--- a/source/slang/slang-ir-link.cpp
+++ b/source/slang/slang-ir-link.cpp
@@ -1830,12 +1830,16 @@ LinkedIR linkIR(
         }
     }
 
+    bool shouldCopyGlobalParams = linkage->m_optionSet.getBoolOption(CompilerOptionName::PreserveParameters);
+
     for (IRModule* irModule : irModules)
     {
         for (auto inst : irModule->getGlobalInsts())
         {
-            // Is it (HLSL) `export` clone
-            if (_isHLSLExported(inst))
+            // We need to copy over exported symbols,
+            // and any global parameters if preserve-params option is set.
+            if (_isHLSLExported(inst) ||
+                shouldCopyGlobalParams && as<IRGlobalParam>(inst))
             {
                 auto cloned = cloneValue(context, inst);
                 if (!cloned->findDecorationImpl(kIROp_KeepAliveDecoration))
diff --git a/source/slang/slang-ir-specialize.cpp b/source/slang/slang-ir-specialize.cpp
index 8fac31a2b..5713b9639 100644
--- a/source/slang/slang-ir-specialize.cpp
+++ b/source/slang/slang-ir-specialize.cpp
@@ -49,7 +49,6 @@ struct SpecializationContext
     IRModule* module;
     DiagnosticSink* sink;
     TargetProgram* targetProgram;
-
     bool changed = false;
 
 
@@ -861,7 +860,7 @@ struct SpecializationContext
             if (iterChanged)
             {
                 this->changed = true;
-                eliminateDeadCode(module->getModuleInst(), IRDeadCodeEliminationOptions());
+                eliminateDeadCode(module->getModuleInst());
             }
 
             // Once the work list has gone dry, we should have the invariant
diff --git a/source/slang/slang-ir-ssa-simplification.cpp b/source/slang/slang-ir-ssa-simplification.cpp
index 2a9c0da43..b8d6360ad 100644
--- a/source/slang/slang-ir-ssa-simplification.cpp
+++ b/source/slang/slang-ir-ssa-simplification.cpp
@@ -24,6 +24,9 @@ namespace Slang
         else
             result.cfgOptions = CFGSimplificationOptions::getDefault();
         result.peepholeOptions = PeepholeOptimizationOptions();
+        if (targetProgram)
+            result.deadCodeElimOptions.keepGlobalParamsAlive = targetProgram->getOptionSet().getBoolOption(CompilerOptionName::PreserveParameters);
+        result.deadCodeElimOptions.useFastAnalysis = result.minimalOptimization;
         return result;
     }
 
@@ -33,6 +36,9 @@ namespace Slang
         result.minimalOptimization = targetProgram ? targetProgram->getOptionSet().shouldPerformMinimumOptimizations() : false;
         result.cfgOptions = CFGSimplificationOptions::getFast();
         result.peepholeOptions = PeepholeOptimizationOptions();
+        if (targetProgram)
+            result.deadCodeElimOptions.keepGlobalParamsAlive = targetProgram->getOptionSet().getBoolOption(CompilerOptionName::PreserveParameters);
+        result.deadCodeElimOptions.useFastAnalysis = result.minimalOptimization;
         return result;
     }
 
@@ -45,8 +51,6 @@ namespace Slang
         const int kMaxIterations = 8;
         const int kMaxFuncIterations = 16;
         int iterationCounter = 0;
-        IRDeadCodeEliminationOptions dceOptions = IRDeadCodeEliminationOptions();
-        dceOptions.useFastAnalysis = options.minimalOptimization;
 
         while (changed && iterationCounter < kMaxIterations)
         {
@@ -79,7 +83,7 @@ namespace Slang
                     // Note: we disregard the `changed` state from dead code elimination pass since
                     // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
                     // DCE will always remove those nearly generated consts and always returns true here.
-                    eliminateDeadCode(func, dceOptions);
+                    eliminateDeadCode(func, options.deadCodeElimOptions);
                     if (funcIterationCount == 0)
                         funcChanged |= constructSSA(func);
                     changed |= funcChanged;
@@ -88,7 +92,7 @@ namespace Slang
             }
             iterationCounter++;
         }
-        eliminateDeadCode(module, dceOptions);
+        eliminateDeadCode(module, options.deadCodeElimOptions);
     }
 
     void simplifyNonSSAIR(TargetProgram* target, IRModule* module, IRSimplificationOptions options)
@@ -96,8 +100,6 @@ namespace Slang
         bool changed = true;
         const int kMaxIterations = 8;
         int iterationCounter = 0;
-        IRDeadCodeEliminationOptions dceOptions = IRDeadCodeEliminationOptions();
-        dceOptions.useFastAnalysis = options.minimalOptimization;
 
         while (changed && iterationCounter < kMaxIterations)
         {
@@ -111,7 +113,7 @@ namespace Slang
             // Note: we disregard the `changed` state from dead code elimination pass since
             // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
             // DCE will always remove those nearly generated consts and always returns true here.
-            eliminateDeadCode(module, dceOptions);
+            eliminateDeadCode(module, options.deadCodeElimOptions);
             iterationCounter++;
         }
     }
@@ -119,9 +121,6 @@ namespace Slang
 
     void simplifyFunc(TargetProgram* target, IRGlobalValueWithCode* func, IRSimplificationOptions options, DiagnosticSink* sink)
     {
-        IRDeadCodeEliminationOptions dceOptions = IRDeadCodeEliminationOptions();
-        dceOptions.useFastAnalysis = options.minimalOptimization;
-
         bool changed = true;
         const int kMaxIterations = 8;
         int iterationCounter = 0;
@@ -140,7 +139,7 @@ namespace Slang
             // Note: we disregard the `changed` state from dead code elimination pass since
             // SCCP pass could be generating temporarily evaluated constant values and never actually use them.
             // DCE will always remove those nearly generated consts and always returns true here.
-            eliminateDeadCode(func, dceOptions);
+            eliminateDeadCode(func, options.deadCodeElimOptions);
 
             changed |= constructSSA(func);
 
diff --git a/source/slang/slang-ir-ssa-simplification.h b/source/slang/slang-ir-ssa-simplification.h
index 166f5a5f3..d524241ae 100644
--- a/source/slang/slang-ir-ssa-simplification.h
+++ b/source/slang/slang-ir-ssa-simplification.h
@@ -3,6 +3,7 @@
 
 #include "slang-ir-simplify-cfg.h"
 #include "slang-ir-peephole.h"
+#include "slang-ir-dce.h"
 
 namespace Slang
 {
@@ -15,6 +16,8 @@ namespace Slang
     {
         CFGSimplificationOptions cfgOptions;
         PeepholeOptimizationOptions peepholeOptions;
+        IRDeadCodeEliminationOptions deadCodeElimOptions;
+
         bool minimalOptimization = false;
 
         static IRSimplificationOptions getDefault(TargetProgram* targetProgram);
diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index 4bbd0dcaf..aefb14deb 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -347,6 +347,7 @@ void initCommandOptions(CommandOptions& options)
         { OptionKind::SourceEmbedLanguage, "-source-embed-language", "-source-embed-language <language>",
         "The language to be used for source embedding. Defaults to C/C++. Currently only C/C++ are supported"},
         { OptionKind::DisableShortCircuit, "-disable-short-circuit", nullptr, "Disable short-circuiting for \"&&\" and \"||\" operations" },
+        { OptionKind::PreserveParameters, "-preserve-params", nullptr, "Preserve all resource parameters in the output code, even if they are not used by the shader."}
     };
 
     _addOptions(makeConstArrayView(generalOpts), options);
@@ -1704,6 +1705,7 @@ SlangResult OptionsParser::_parse(
             case OptionKind::NoHLSLBinding:
             case OptionKind::NoHLSLPackConstantBufferElements:
             case OptionKind::LoopInversion:
+            case OptionKind::PreserveParameters:
                 linkage->m_optionSet.set(optionKind, true); break;
                 break;
             case OptionKind::MatrixLayoutRow:
diff --git a/tests/spirv/preserve-param.slang b/tests/spirv/preserve-param.slang
new file mode 100644
index 000000000..e9cc82291
--- /dev/null
+++ b/tests/spirv/preserve-param.slang
@@ -0,0 +1,19 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -preserve-params -O0
+
+// Test that -preserve-params option preserves shader paraemter declarations in the output spirv code.
+
+// CHECK-DAG: OpDecorate %{{.*}} Binding 0
+
+// CHECK-DAG: OpDecorate %{{.*}} Binding 1
+
+RWStructuredBuffer<float> buffer;
+
+struct TT
+{
+    Texture2D tex;    
+}
+[numthreads(1, 1, 1)]
+void f(ConstantBuffer<TT> t)
+{
+    return;
+}
\ No newline at end of file