[ValueTracking] Add with.overflow intrinsics to poison analysis functions

This is a patch teaching ValueTracking that `s/u*.with.overflow` intrinsics do not
create undef/poison and they propagate poison.
I couldn't write a nice example like the one with ctpop; ValueTrackingTest.cpp were simply updated
to check these instead.
This patch helps reducing regression while fixing https://llvm.org/pr49688 .

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D99671

1 files changed, 23 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 39d8f9b..e5c3f3f 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4887,6 +4887,12 @@ static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly) {
       switch (II->getIntrinsicID()) {
       // TODO: Add more intrinsics.
       case Intrinsic::ctpop:
+      case Intrinsic::sadd_with_overflow:
+      case Intrinsic::ssub_with_overflow:
+      case Intrinsic::smul_with_overflow:
+      case Intrinsic::uadd_with_overflow:
+      case Intrinsic::usub_with_overflow:
+      case Intrinsic::umul_with_overflow:
         return false;
       }
     }
@@ -5214,9 +5220,25 @@ bool llvm::propagatesPoison(const Operator *I) {
   case Instruction::Freeze:
   case Instruction::Select:
   case Instruction::PHI:
-  case Instruction::Call:
   case Instruction::Invoke:
     return false;
+  case Instruction::Call:
+    if (auto *II = dyn_cast<IntrinsicInst>(I)) {
+      switch (II->getIntrinsicID()) {
+      // TODO: Add more intrinsics.
+      case Intrinsic::sadd_with_overflow:
+      case Intrinsic::ssub_with_overflow:
+      case Intrinsic::smul_with_overflow:
+      case Intrinsic::uadd_with_overflow:
+      case Intrinsic::usub_with_overflow:
+      case Intrinsic::umul_with_overflow:
+        // If an input is a vector containing a poison element, the
+        // two output vectors (calculated results, overflow bits)'
+        // corresponding lanes are poison.
+        return true;
+      }
+    }
+    return false;
   case Instruction::ICmp:
   case Instruction::FCmp:
   case Instruction::GetElementPtr: