[PATCH] D114647: [TrivialDeadness] Introduce API separating two different usages

[Anna Thomas via Phabricator via llvm-commits]

anna updated this revision to Diff 391089.
anna added a comment.

updated to correct diff.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D114647/new/

https://reviews.llvm.org/D114647

Files:
  llvm/include/llvm/Transforms/Utils/Local.h
  llvm/lib/Transforms/Utils/Local.cpp


Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -402,6 +402,18 @@
   return wouldInstructionBeTriviallyDead(I, TLI);
 }
 
+bool llvm::wouldInstructionBeTriviallyDeadOnUnusedPaths(
+    Instruction *I, const TargetLibraryInfo *TLI) {
+  // Instructions that are "markers" and have implied meaning on code around
+  // them (without explicit uses), are not dead on unused paths.
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+    if (II->getIntrinsicID() == Intrinsic::stacksave ||
+        II->getIntrinsicID() == Intrinsic::launder_invariant_group ||
+        II->isLifetimeStartOrEnd())
+      return false;
+  return wouldInstructionBeTriviallyDead(I, TLI);
+}
+
 bool llvm::wouldInstructionBeTriviallyDead(Instruction *I,
                                            const TargetLibraryInfo *TLI) {
   if (I->isTerminator())
Index: llvm/include/llvm/Transforms/Utils/Local.h
===================================================================
--- llvm/include/llvm/Transforms/Utils/Local.h
+++ llvm/include/llvm/Transforms/Utils/Local.h
@@ -90,6 +90,14 @@
 bool wouldInstructionBeTriviallyDead(Instruction *I,
                                      const TargetLibraryInfo *TLI = nullptr);
 
+/// Return true if the result produced by the instruction has no side effects on
+/// any paths other than where it is used. This is less conservative than 
+/// wouldInstructionBeTriviallyDead which is based on the assumption
+/// that the use count will be 0. An example usage of this API is for
+/// identifying instructions that can be sunk down to use(s).
+bool wouldInstructionBeTriviallyDeadOnUnusedPaths(
+    Instruction *I, const TargetLibraryInfo *TLI = nullptr);
+
 /// If the specified value is a trivially dead instruction, delete it.
 /// If that makes any of its operands trivially dead, delete them too,
 /// recursively. Return true if any instructions were deleted.


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