diff options
| -rw-r--r-- | source/slang/slang-ir-autodiff-unzip.cpp | 14 | ||||
| -rw-r--r-- | source/slang/slang-ir-util.cpp | 50 |
2 files changed, 45 insertions, 19 deletions
diff --git a/source/slang/slang-ir-autodiff-unzip.cpp b/source/slang/slang-ir-autodiff-unzip.cpp index 16862bb19..7e01fde28 100644 --- a/source/slang/slang-ir-autodiff-unzip.cpp +++ b/source/slang/slang-ir-autodiff-unzip.cpp @@ -581,20 +581,6 @@ IRFunc* DiffUnzipPass::extractPrimalFunc( } instsToRemove.add(inst); } - else if (auto primalCtx = inst->findDecoration<IRBackwardDerivativePrimalContextDecoration>()) - { - if (inst->getOp() == kIROp_Call) - { - // The primal calls should be marked as no side effect so they can be DCE'd if possible. - // We can only do so if the intermediate context of the callee is stored. - // - if (primalCtx->getBackwardDerivativePrimalContextVar() - ->findDecoration<IRPrimalValueStructKeyDecoration>()) - { - builder.addSimpleDecoration<IRNoSideEffectDecoration>(inst); - } - } - } } } diff --git a/source/slang/slang-ir-util.cpp b/source/slang/slang-ir-util.cpp index de03a1661..a27afee8a 100644 --- a/source/slang/slang-ir-util.cpp +++ b/source/slang/slang-ir-util.cpp @@ -609,17 +609,57 @@ bool isPureFunctionalCall(IRCall* call) { // 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; + IRFunc* parentFunc = nullptr; for (UInt i = 0; i < call->getArgCount(); i++) { - if (isValueType(call->getArg(i)->getDataType())) + auto arg = call->getArg(i); + if (isValueType(arg->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; + if (!parentFunc) + { + parentFunc = getParentFunc(call); + if (!parentFunc) + return false; + } + + if (arg->getOp() == kIROp_Var && getParentFunc(arg) == parentFunc) + { + // If the pointer argument is a local variable (thus can't alias with other addresses) + // and it is never read from in the function, we can safely treat the call as having + // no side-effect. + // This is a conservative test, but is sufficient to detect the most common case where + // a temporary variable is used as the inout argument and the result stored in the temp + // variable isn't being used elsewhere in the parent func. + // + // A more aggresive test can check all other address uses reachable from the call site + // and see if any of them are aliasing with the argument. + for (auto use = arg->firstUse; use; use = use->nextUse) + { + if (as<IRDecoration>(use->getUser())) + continue; + switch (use->getUser()->getOp()) + { + case kIROp_Store: + // We are fine with stores into the variable, since store operations + // are not dependent on whatever we do in the call here. + continue; + default: + // We have some other unknown use of the variable address, they can + // be loads, or calls using addresses derived from the variable, + // we will treat the call as having side effect to be safe. + return false; + } + } + } + else + { + return false; + } } - return !hasOutArg; + return true; } return false; } |