Fix data-flow analysis not propagating diff property through differentiable calls (#3010)

* Add test for nodiff diagnostic for non-diff call propagated through diff call

* Add logic to disambiguate calls to differentiable and non-differentiable methods

* Add expected results for test

* Simplify test

* Update slang-ir-check-differentiability.cpp

* Added comments for TreatAsDifferentiableExpr flavors

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/source/slang/slang-ir-check-differentiability.cpp b/source/slang/slang-ir-check-differentiability.cpp
index d4b93be5e..3207e0729 100644
--- a/source/slang/slang-ir-check-differentiability.cpp
+++ b/source/slang/slang-ir-check-differentiability.cpp
@@ -71,6 +71,15 @@ public:
         return false;
     }
 
+    bool shouldTreatCallAsDifferentiable(IRInst* callInst)
+    {
+        SLANG_ASSERT(as<IRCall>(callInst));
+
+        return (
+            callInst->findDecoration<IRTreatCallAsDifferentiableDecoration>() || 
+            callInst->findDecoration<IRDifferentiableCallDecoration>());
+    }
+
     bool isDifferentiableFunc(IRInst* func, DifferentiableLevel level)
     {
         switch (func->getOp())
@@ -300,7 +309,7 @@ public:
             case kIROp_FloatLit:
                 return true;
             case kIROp_Call:
-                return inst->findDecoration<IRTreatAsDifferentiableDecoration>() ||
+                return shouldTreatCallAsDifferentiable(inst) ||
                     isDifferentiableFunc(as<IRCall>(inst)->getCallee(), requiredDiffLevel) && isDifferentiableType(diffTypeContext, inst->getFullType());
             case kIROp_Load:
                 // We don't have more knowledge on whether diff is available at the destination address.
@@ -330,7 +339,7 @@ public:
             case kIROp_DetachDerivative:
                 return false;
             case kIROp_Call:
-                if (inst->findDecoration<IRTreatAsDifferentiableDecoration>())
+                if (shouldTreatCallAsDifferentiable(inst))
                     return false;
                 return isDifferentiableFunc(as<IRCall>(inst)->getCallee(), requiredDiffLevel) &&
                        isDifferentiableType(diffTypeContext, inst->getFullType());
@@ -451,7 +460,8 @@ public:
                     // If inst's type is differentiable, and it is in expectDiffInstWorkList,
                     // then some user is expecting the result of the call to produce a derivative.
                     // In this case we need to issue a diagnostic.
-                    if (isDifferentiableType(diffTypeContext, inst->getFullType()))
+                    if (isDifferentiableType(diffTypeContext, inst->getFullType()) && 
+                        !isDifferentiableFunc(call->getCallee(), requiredDiffLevel))
                     {
                         sink->diagnose(
                             inst,
@@ -490,9 +500,7 @@ public:
             case kIROp_Call:
             {
                 auto callInst = as<IRCall>(inst);
-                if (callInst->findDecoration<IRTreatAsDifferentiableDecoration>())
-                    continue;
-                if (!isDifferentiableFunc(callInst->getCallee(), DifferentiableLevel::Forward))
+                if (callInst->findDecoration<IRTreatCallAsDifferentiableDecoration>())
                     continue;
                 auto calleeFuncType = as<IRFuncType>(callInst->getCallee()->getFullType());
                 if (!calleeFuncType) continue;