[ValueTracking] Take poison-generating metadata into account (PR59888)

In canCreateUndefOrPoison(), take not only poison-generating flags,
but also poison-generating metadata into account. The helpers are
written generically, but I believe the only case that can actually
matter is !range on calls -- !nonnull and !align are only valid on
loads, and those can create undef/poison anyway.

Unfortunately, this negatively impacts logical to bitwise and/or
conversion: For ctpop/ctlz/cttz we always attach !range metadata,
which will now block the transform, because it might introduce
poison. It would be possible to recover this regression by supporting
a ConsiderFlagsAndMetadata=false mode in impliesPoison() and clearing
flags/metadata on visited instructions.

Fixes https://github.com/llvm/llvm-project/issues/59888.

Differential Revision: https://reviews.llvm.org/D142115

1 files changed, 9 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 7c38c60..55fd419 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5236,9 +5236,9 @@ static bool shiftAmountKnownInRange(const Value *ShiftAmount) {
 }
 
 static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
-                                   bool ConsiderFlags) {
+                                   bool ConsiderFlagsAndMetadata) {
 
-  if (ConsiderFlags && Op->hasPoisonGeneratingFlags())
+  if (ConsiderFlagsAndMetadata && Op->hasPoisonGeneratingFlagsOrMetadata())
     return true;
 
   unsigned Opcode = Op->getOpcode();
@@ -5386,12 +5386,15 @@ static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
   }
 }
 
-bool llvm::canCreateUndefOrPoison(const Operator *Op, bool ConsiderFlags) {
-  return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/false, ConsiderFlags);
+bool llvm::canCreateUndefOrPoison(const Operator *Op,
+                                  bool ConsiderFlagsAndMetadata) {
+  return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/false,
+                                  ConsiderFlagsAndMetadata);
 }
 
-bool llvm::canCreatePoison(const Operator *Op, bool ConsiderFlags) {
-  return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/true, ConsiderFlags);
+bool llvm::canCreatePoison(const Operator *Op, bool ConsiderFlagsAndMetadata) {
+  return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/true,
+                                  ConsiderFlagsAndMetadata);
 }
 
 static bool directlyImpliesPoison(const Value *ValAssumedPoison,