From c31577953d5041c82375c22d847c2eba06106c58 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 25 Feb 2022 20:49:31 -0800
Subject: Improved SCCP, inlining and resource specialization passes, legalize
 `ImageSubscript` for GLSL (#2146)

---
 source/slang/slang-ir-simplify-cfg.cpp | 82 ++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 source/slang/slang-ir-simplify-cfg.cpp

(limited to 'source/slang/slang-ir-simplify-cfg.cpp')

diff --git a/source/slang/slang-ir-simplify-cfg.cpp b/source/slang/slang-ir-simplify-cfg.cpp
new file mode 100644
index 000000000..af0e7c0ce
--- /dev/null
+++ b/source/slang/slang-ir-simplify-cfg.cpp
@@ -0,0 +1,82 @@
+#include "slang-ir-simplify-cfg.h"
+
+#include "slang-ir-insts.h"
+#include "slang-ir.h"
+
+namespace Slang
+{
+
+bool processFunc(IRFunc* func)
+{
+    auto firstBlock = func->getFirstBlock();
+    if (!firstBlock)
+        return false;
+
+    bool changed = false;
+
+    List<IRBlock*> workList;
+    HashSet<IRBlock*> processedBlock;
+    workList.add(func->getFirstBlock());
+    while (workList.getCount())
+    {
+        auto block = workList.getFirst();
+        workList.fastRemoveAt(0);
+        while (block)
+        {
+            // If `block` does not end with an unconditional branch, bail.
+            if (block->getTerminator()->getOp() != kIROp_unconditionalBranch)
+                break;
+            auto branch = as<IRUnconditionalBranch>(block->getTerminator());
+            auto successor = branch->getTargetBlock();
+            // Only perform the merge if `block` is the only predecessor of `successor`.
+            // We also need to make sure not to merge a block that serves as the
+            // merge point in CFG. Such blocks will have more than one use.
+            if (successor->hasMoreThanOneUse())
+                break;
+            changed = true;
+            Index paramIndex = 0;
+            auto inst = successor->getFirstDecorationOrChild();
+            while (inst)
+            {
+                auto next = inst->getNextInst();
+                if (inst->getOp() == kIROp_Param)
+                {
+                    inst->replaceUsesWith(branch->getArg(paramIndex));
+                    paramIndex++;
+                }
+                else
+                {
+                    inst->removeFromParent();
+                    inst->insertAtEnd(block);
+                }
+                inst = next;
+            }
+            branch->removeAndDeallocate();
+            assert(!successor->hasUses());
+            successor->removeAndDeallocate();
+        }
+        for (auto successor : block->getSuccessors())
+        {
+            if (processedBlock.Add(successor))
+            {
+                workList.add(successor);
+            }
+        }
+    }
+    return changed;
+}
+
+bool simplifyCFG(IRModule* module)
+{
+    bool changed = false;
+    for (auto inst : module->getGlobalInsts())
+    {
+        if (auto func = as<IRFunc>(inst))
+        {
+            changed |= processFunc(func);
+        }
+    }
+    return changed;
+}
+
+} // namespace Slang
-- 
cgit v1.2.3