Overhauled reverse-mode control flow handling (#2608)

* Added switch-case support; fixed non-diff parameter transposition

* Made region propagation much more robust. Partial loop unzip implementation

* WIP: Added most loop handling code, and a test. Still untested

* Added CFG Normalization pass + CFG Reversal Pass + Loop Unzipping + most loop transcription

* Add single-iter-loop test.

* proj files

* removed comments

* Update reverse-loop.slang

* Removed out-of-date code

* Disabled IR validation during constructSSA phase of normalizeCFG. constructSSA now reuses sharedBuilder

* Moved normalizeCFG() call to prepareFuncForBackwardDiff()

1 files changed, 20 insertions, 3 deletions

diff --git a/source/slang/slang-ir-ssa.cpp b/source/slang/slang-ir-ssa.cpp
index 0bd5c6e9f..ee55a6546 100644
--- a/source/slang/slang-ir-ssa.cpp
+++ b/source/slang/slang-ir-ssa.cpp
@@ -84,7 +84,7 @@ struct ConstructSSAContext
     Dictionary<IRBlock*, RefPtr<SSABlockInfo>> blockInfos;
 
     // IR building state to use during the operation
-    SharedIRBuilder sharedBuilder;
+    SharedIRBuilder* sharedBuilder;
 
     // Instructions to remove during cleanup
     List<IRInst*> instsToRemove;
@@ -1043,7 +1043,7 @@ static void breakCriticalEdges(
 
     for (auto edge : criticalEdges)
     {
-        context->sharedBuilder.insertBlockAlongEdge(edge);
+        context->sharedBuilder->insertBlockAlongEdge(edge);
     }
 }
 
@@ -1205,7 +1205,8 @@ bool constructSSA(IRModule* module, IRGlobalValueWithCode* globalVal)
     ConstructSSAContext context;
     context.globalVal = globalVal;
 
-    context.sharedBuilder.init(module);
+    SharedIRBuilder sharedBuilder(module);
+    context.sharedBuilder = &sharedBuilder;
 
     context.builder.init(context.sharedBuilder);
     context.builder.setInsertInto(module);
@@ -1213,6 +1214,22 @@ bool constructSSA(IRModule* module, IRGlobalValueWithCode* globalVal)
     return constructSSA(&context);
 }
 
+// Construct SSA form for a global value with code and reuse 
+// an existing sharedBuilder
+//
+bool constructSSA(SharedIRBuilder* sharedBuilder, IRGlobalValueWithCode* globalVal)
+{
+    ConstructSSAContext context;
+    context.globalVal = globalVal;
+    
+    context.sharedBuilder = sharedBuilder;
+
+    context.builder.init(sharedBuilder);
+    context.builder.setInsertInto(sharedBuilder->getModule());
+
+    return constructSSA(&context);
+}
+
 bool constructSSA(IRModule* module, IRInst* globalVal)
 {
     switch (globalVal->getOp())