[IsKnownNonZero] Handle the case with non-constant phi nodes

Handle the case when all inputs of phi are proven to be non zero.

Constants are checked in beginning of this method before check for depth of recursion,
so it is a partial case of non-constant phi.

Recursion depth is already handled by the function.

Reviewers: aqjune, nikic, efriedma
Reviewed By: nikic
Subscribers: dantrushin, hiraditya, jdoerfert, llvm-commits
Differential Revision: https://reviews.llvm.org/D88276

Author: Serguei Katkov

llvm/lib/Analysis/ValueTracking.cpp

@@ -2561,11 +2561,16 @@ bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
         }
       }
     }
-    // Check if all incoming values are non-zero constant.
-    bool AllNonZeroConstants = llvm::all_of(PN->operands(), [](Value *V) {
-      return isa<ConstantInt>(V) && !cast<ConstantInt>(V)->isZero();
+    // Check if all incoming values are non-zero using recursion.
+    Query RecQ = Q;
+    unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
+    bool AllNonZero = llvm::all_of(PN->operands(), [&](const Use &U) {
+      if (U.get() == PN)
+        return true;
+      RecQ.CxtI = PN->getIncomingBlock(U)->getTerminator();
+      return isKnownNonZero(U.get(), DemandedElts, NewDepth, RecQ);
     });
-    if (AllNonZeroConstants)
+    if (AllNonZero)
       return true;
   }
   // ExtractElement

llvm/test/Transforms/InstCombine/phi.ll

@@ -1056,6 +1056,35 @@ if.end:                                           ; preds = %if.else, %if.then
   ret i1 %cmp1
 }
 
+define i1 @phi_allnonzerononconstant(i1 %c, i32 %a, i32* nonnull %b1, i32* nonnull %b2) {
+; CHECK-LABEL: @phi_allnonzerononconstant(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    br label [[IF_END:%.*]]
+; CHECK:       if.else:
+; CHECK-NEXT:    call void @dummy()
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    ret i1 false
+;
+entry:
+  br i1 %c, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  call void @dummy()
+
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %x.0 = phi i32* [ %b1, %if.then ], [ %b2, %if.else ]
+  %cmp1 = icmp eq i32* %x.0, null
+  ret i1 %cmp1
+}
+
 declare void @dummy()
 
 define i1 @phi_knownnonzero_eq(i32 %n, i32 %s, i32* nocapture readonly %P) {