[PATCH] D79748: [ValueTracking] And & Or propagate poison.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: aqjune, nlopes, reames.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

Both And and Or instructions propagate poison if any operand is poison.
Note the TODO in the function that most instructions expect a few should
propagate poison, but it is probably safer to enable them step-by-step.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79748

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Analysis/ScalarEvolution/nsw.ll


Index: llvm/test/Analysis/ScalarEvolution/nsw.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/nsw.ll
+++ llvm/test/Analysis/ScalarEvolution/nsw.ll
@@ -223,8 +223,26 @@
   ret void
 }
 
-define void @bad_postinc_nsw_b(i32 %n) {
-; CHECK-LABEL: Classifying expressions for: @bad_postinc_nsw_b
+define void @bad_postinc_nsw_b_or(i32 %n) {
+; CHECK-LABEL: Classifying expressions for: @bad_postinc_nsw_b_or
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
+  %iv.inc = add nsw i32 %iv, 7
+  %iv.inc.and = or i32 %iv.inc, 0
+; CHECK:    %iv.inc = add nsw i32 %iv, 7
+; CHECK-NEXT:  -->  {7,+,7}<nuw><nsw><%loop>
+  %becond = icmp ult i32 %iv.inc.and, %n
+  br i1 %becond, label %loop, label %leave
+
+leave:
+  ret void
+}
+
+define void @bad_postinc_nsw_b_and(i32 %n) {
+; CHECK-LABEL: Classifying expressions for: @bad_postinc_nsw_b_and
 entry:
   br label %loop
 
@@ -233,7 +251,7 @@
   %iv.inc = add nsw i32 %iv, 7
   %iv.inc.and = and i32 %iv.inc, 0
 ; CHECK:    %iv.inc = add nsw i32 %iv, 7
-; CHECK-NEXT:  -->  {7,+,7}<nuw><%loop>
+; CHECK-NEXT:  -->  {7,+,7}<nuw><nsw><%loop>
   %becond = icmp ult i32 %iv.inc.and, %n
   br i1 %becond, label %loop, label %leave
 
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4950,6 +4950,8 @@
   case Instruction::Mul:
   case Instruction::Shl:
   case Instruction::GetElementPtr:
+  case Instruction::And:
+  case Instruction::Or:
     // These operations all propagate poison unconditionally. Note that poison
     // is not any particular value, so xor or subtraction of poison with
     // itself still yields poison, not zero.


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