Revert r246232 and r246304.

This reverts isSafeToSpeculativelyExecute's use of ReadNone until we
split ReadNone into two pieces: one attribute which reasons about how
the function reasons about memory and another attribute which determines
how it may be speculated, CSE'd, trap, etc.

llvm-svn: 246331

1 files changed, 12 insertions, 10 deletions

diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index 33ad88358e5..98d4c8afc7b 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -506,16 +506,18 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
 
   // If I will have a chain, make sure no other instruction that will have a
   // chain interposes between I and the return.
-  for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
-    if (&*BBI == I)
-      break;
-    // Debug info intrinsics do not get in the way of tail call optimization.
-    if (isa<DbgInfoIntrinsic>(BBI))
-      continue;
-    if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
-        !isSafeToSpeculativelyExecute(BBI))
-      return false;
-  }
+  if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
+      !isSafeToSpeculativelyExecute(I))
+    for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
+      if (&*BBI == I)
+        break;
+      // Debug info intrinsics do not get in the way of tail call optimization.
+      if (isa<DbgInfoIntrinsic>(BBI))
+        continue;
+      if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
+          !isSafeToSpeculativelyExecute(BBI))
+        return false;
+    }
 
   const Function *F = ExitBB->getParent();
   return returnTypeIsEligibleForTailCall(