Ensure we're commuting instructions only when internal one has a single

use. Fix couple of similar single use predicates while there.

Fixes #78848

Author: asl

lib/SILOptimizer/SILCombiner/SILCombinerCastVisitors.cpp

@@ -790,7 +790,7 @@ SILInstruction *SILCombiner::visitConvertEscapeToNoEscapeInst(
   //
   // This unblocks the `thin_to_thick_function` peephole optimization below.
   if (auto *CFI = dyn_cast<ConvertFunctionInst>(Cvt->getOperand())) {
-    if (CFI->getSingleUse()) {
+    if (hasOneNonDebugUse(CFI)) {
       if (auto *TTTFI = dyn_cast<ThinToThickFunctionInst>(CFI->getOperand())) {
         if (TTTFI->getSingleUse()) {
           auto convertedThickType = CFI->getType().castTo<SILFunctionType>();
@@ -836,7 +836,7 @@ SILInstruction *SILCombiner::visitConvertEscapeToNoEscapeInst(
   // %vjp' = convert_escape_to_noescape %vjp
   // %y = differentiable_function(%orig', %jvp', %vjp')
   if (auto *DFI = dyn_cast<DifferentiableFunctionInst>(Cvt->getOperand())) {
-    if (DFI->hasOneUse()) {
+    if (hasOneNonDebugUse(DFI)) {
       auto createConvertEscapeToNoEscape =
         [&](NormalDifferentiableFunctionTypeComponent extractee) {
           if (!DFI->hasExtractee(extractee))
@@ -1020,9 +1020,7 @@ SILCombiner::visitConvertFunctionInst(ConvertFunctionInst *cfi) {
   // %vjp' = convert_function %vjp
   // %y = differentiable_function(%orig', %jvp', %vjp')
   if (auto *DFI = dyn_cast<DifferentiableFunctionInst>(cfi->getOperand())) {
-    // Workaround for a problem with OSSA: https://github.com/swiftlang/swift/issues/78848
-    // TODO: remove this if-statement once the underlying problem is fixed.
-    if (cfi->getFunction()->hasOwnership())
+    if (!hasOneNonDebugUse(DFI))
       return nullptr;
 
     auto createConvertFunctionOfComponent =