[IR] Move willReturn() to Instruction

This moves the willReturn() helper from CallBase to Instruction,
so that it can be used in a more generic manner. This will make
it easier to fix additional passes (ADCE and BDCE), and will give
us one place to change if additional instructions should become
non-willreturn (e.g. there has been talk about handling volatile
operations this way).

I have also included the IntrinsicInst workaround directly in
here, so that it gets applied consistently. (As such this change
is not entirely NFC -- FuncAttrs will now use this as well.)

Differential Revision: https://reviews.llvm.org/D96992

1 files changed, 3 insertions, 25 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 493eb08..edf165c 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5056,36 +5056,14 @@ bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
   // arbitrary length of time, but programs aren't allowed to rely on that.
 
   // If there is no successor, then execution can't transfer to it.
-  if (const auto *CRI = dyn_cast<CleanupReturnInst>(I))
-    return !CRI->unwindsToCaller();
-  if (const auto *CatchSwitch = dyn_cast<CatchSwitchInst>(I))
-    return !CatchSwitch->unwindsToCaller();
-  if (isa<ResumeInst>(I))
-    return false;
   if (isa<ReturnInst>(I))
     return false;
   if (isa<UnreachableInst>(I))
     return false;
 
-  // Calls can throw, or contain an infinite loop, or kill the process.
-  if (const auto *CB = dyn_cast<CallBase>(I)) {
-    // Call sites that throw have implicit non-local control flow.
-    if (!CB->doesNotThrow())
-      return false;
-
-    // A function which doens't throw and has "willreturn" attribute will
-    // always return.
-    if (CB->hasFnAttr(Attribute::WillReturn))
-      return true;
-
-    // FIXME: Temporarily assume that all side-effect free intrinsics will
-    // return. Remove this workaround once all intrinsics are appropriately
-    // annotated.
-    return isa<IntrinsicInst>(CB) && CB->onlyReadsMemory();
-  }
-
-  // Other instructions return normally.
-  return true;
+  // An instruction that returns without throwing must transfer control flow
+  // to a successor.
+  return !I->mayThrow() && I->willReturn();
 }
 
 bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {