From bd6306cdaa4a49344658bd026721b6532e103d09 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 24 Feb 2023 10:01:47 -0800
Subject: More control flow simplifications. (#2673)

* More control flow and Phi param simplifications.

* Fix.

* Fix gcc error.

* Fix.

* More IR cleanup.

* Fix bug in phi param dce + ifelse simplify.

* Propagate and DCE side-effect-free functions.

* Enhance CFG simplifcation to remove loops with no side effects.

* Fix.

* Fixes.

* Fix tests. Add [__AlwaysFoldIntoUseSite] for rayPayloadLocation.

* More cleanup.

* Fixes.

* Fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>
---
 source/slang/slang-ir-util.cpp | 75 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 64 insertions(+), 11 deletions(-)

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

diff --git a/source/slang/slang-ir-util.cpp b/source/slang/slang-ir-util.cpp
index 3db036a8d..339521f41 100644
--- a/source/slang/slang-ir-util.cpp
+++ b/source/slang/slang-ir-util.cpp
@@ -157,6 +157,32 @@ IRInst* maybeSpecializeWithGeneric(IRBuilder& builder, IRInst* genericToSpecaili
     return genericToSpecailize;
 }
 
+bool isValueType(IRInst* dataType)
+{
+    dataType = getResolvedInstForDecorations(unwrapAttributedType(dataType));
+    if (as<IRBasicType>(dataType))
+        return true;
+    switch (dataType->getOp())
+    {
+    case kIROp_StructType:
+    case kIROp_InterfaceType:
+    case kIROp_ClassType:
+    case kIROp_VectorType:
+    case kIROp_MatrixType:
+    case kIROp_TupleType:
+    case kIROp_ResultType:
+    case kIROp_OptionalType:
+    case kIROp_DifferentialPairType:
+    case kIROp_DynamicType:
+    case kIROp_AnyValueType:
+    case kIROp_ArrayType:
+    case kIROp_FuncType:
+        return true;
+    default:
+        return false;
+    }
+}
+
 IRInst* hoistValueFromGeneric(IRBuilder& inBuilder, IRInst* value, IRInst*& outSpecializedVal, bool replaceExistingValue)
 {
     auto outerGeneric = as<IRGeneric>(findOuterGeneric(value));
@@ -402,8 +428,7 @@ bool canInstHaveSideEffectAtAddress(IRGlobalValueWithCode* func, IRInst* inst, I
             {
                 auto callee = call->getCallee();
                 if (callee &&
-                    callee->findDecoration<IRReadNoneDecoration>() &&
-                    callee->findDecoration<IRNoSideEffectDecoration>())
+                    callee->findDecoration<IRReadNoneDecoration>())
                 {
                     // An exception is if the callee is side-effect free and is not reading from
                     // memory.
@@ -423,6 +448,32 @@ bool canInstHaveSideEffectAtAddress(IRGlobalValueWithCode* func, IRInst* inst, I
                     if (canAddressesPotentiallyAlias(func, call->getArg(i), addr))
                         return true;
                 }
+                else if (!isValueType(call->getArg(i)->getDataType()))
+                {
+                    // This is some unknown handle type, we assume it can have any side effects.
+                    return true;
+                }
+            }
+        }
+        break;
+    case kIROp_unconditionalBranch:
+    case kIROp_loop:
+        {
+            auto branch = as<IRUnconditionalBranch>(inst);
+            // If any pointer typed argument of the branch inst may overlap addr, return true.
+            for (UInt i = 0; i < branch->getArgCount(); i++)
+            {
+                SLANG_RELEASE_ASSERT(branch->getArg(i)->getDataType());
+                if (isPtrLikeOrHandleType(branch->getArg(i)->getDataType()))
+                {
+                    if (canAddressesPotentiallyAlias(func, branch->getArg(i), addr))
+                        return true;
+                }
+                else if (!isValueType(branch->getArg(i)->getDataType()))
+                {
+                    // This is some unknown handle type, we assume it can have any side effects.
+                    return true;
+                }
             }
         }
         break;
@@ -434,6 +485,11 @@ bool canInstHaveSideEffectAtAddress(IRGlobalValueWithCode* func, IRInst* inst, I
             if (isPtrLikeOrHandleType(inst->getOperand(0)->getDataType()) &&
                 canAddressesPotentiallyAlias(func, inst->getOperand(0), addr))
                 return true;
+            else if (!isValueType(inst->getOperand(0)->getDataType()))
+            {
+                // This is some unknown handle type, we assume it can have any side effects.
+                return true;
+            }
         }
         break;
     default:
@@ -519,21 +575,18 @@ bool isPureFunctionalCall(IRCall* call)
 {
     auto callee = getResolvedInstForDecorations(call->getCallee());
     if (callee->findDecoration<IRReadNoneDecoration>())
-    {
-        return true;
-    }
-    if (callee->findDecoration<IRNoSideEffectDecoration>())
     {
         // If the function has no side effect and is not writing to any outputs,
         // we can safely treat the call as a normal inst.
         bool hasOutArg = false;
         for (UInt i = 0; i < call->getArgCount(); i++)
         {
-            if (as<IRPtrTypeBase>(call->getArg(i)->getDataType()))
-            {
-                hasOutArg = true;
-                break;
-            }
+            if (isValueType(call->getArg(i)->getDataType()))
+                continue;
+            // If the argument type is not a known value type,
+            // assume it is a pointer or handle through which side effect can take place.
+            hasOutArg = true;
+            break;
         }
         return !hasOutArg;
     }
-- 
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