[inst-simplify] Fail simplification if we have ownership and are not passed a non-null deadEndBlocks.

I am trying to be more careful about this rather than letting someone make this
mistake in the future. I also added some comments and a DeadEndBlocks instance
to TempRValueElimination so that it gets full simplifications in OSSA.

Author: gottesmm

include/swift/SILOptimizer/Analysis/SimplifyInstruction.h

@@ -45,6 +45,8 @@ replaceAllSimplifiedUsesAndErase(SILInstruction *I, SILValue result,
 ///
 /// NOTE: When OSSA is enabled this API assumes OSSA is properly formed and will
 /// insert compensating instructions.
+/// NOTE: When \p I is in an OSSA function, this fails to optimize if \p
+/// deadEndBlocks is null.
 SILBasicBlock::iterator simplifyAndReplaceAllSimplifiedUsesAndErase(
     SILInstruction *I, InstModCallbacks &callbacks,
     DeadEndBlocks *deadEndBlocks = nullptr);

lib/SILOptimizer/Analysis/SimplifyInstruction.cpp

@@ -793,6 +793,11 @@ SILBasicBlock::iterator swift::simplifyAndReplaceAllSimplifiedUsesAndErase(
   if (!svi->getFunction()->hasOwnership())
     return replaceAllUsesAndErase(svi, result, callbacks);
 
+  // If we weren't passed a dead end blocks, we can't optimize without ownership
+  // enabled.
+  if (!deadEndBlocks)
+    return next;
+
   JointPostDominanceSetComputer computer(*deadEndBlocks);
   OwnershipFixupContext ctx{callbacks, *deadEndBlocks, computer};
   OwnershipRAUWHelper helper(ctx, svi, result);

lib/SILOptimizer/Mandatory/OwnershipModelEliminator.cpp

@@ -482,6 +482,7 @@ static bool stripOwnership(SILFunction &func) {
     InstModCallbacks callbacks([&](SILInstruction *instToErase) {
       visitor.eraseInstruction(instToErase);
     });
+    // We are no longer in OSSA, so we don't need to pass in a deBlocks.
     simplifyAndReplaceAllSimplifiedUsesAndErase(*value, callbacks);
     madeChange |= callbacks.hadCallbackInvocation();
   }

lib/SILOptimizer/Transforms/TempRValueElimination.cpp

@@ -17,7 +17,9 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "sil-temp-rvalue-opt"
+
 #include "swift/SIL/DebugUtils.h"
+#include "swift/SIL/BasicBlockUtils.h"
 #include "swift/SIL/MemAccessUtils.h"
 #include "swift/SIL/SILArgument.h"
 #include "swift/SIL/SILBuilder.h"
@@ -749,14 +751,15 @@ void TempRValueOptPass::run() {
 #endif
   };
 
+  DeadEndBlocks deBlocks(getFunction());
   for (auto *deadCopy : deadCopies) {
     assert(changed);
     auto *srcInst = deadCopy->getSrc()->getDefiningInstruction();
     deadCopy->eraseFromParent();
     // Simplify any access scope markers that were only used by the dead
     // copy_addr and other potentially unused addresses.
     if (srcInst) {
-      simplifyAndReplaceAllSimplifiedUsesAndErase(srcInst, callbacks);
+      simplifyAndReplaceAllSimplifiedUsesAndErase(srcInst, callbacks, &deBlocks);
     }
   }
   if (changed) {