[llvm] 297ec61 - [IsKnownNonZero] Handle the case with non-constant phi nodes

[Serguei Katkov via llvm-commits]

Author: Serguei Katkov
Date: 2020-09-29T15:22:10+07:00
New Revision: 297ec611304663931be52e6118d9f135ceb8a027

URL: https://github.com/llvm/llvm-project/commit/297ec611304663931be52e6118d9f135ceb8a027
DIFF: https://github.com/llvm/llvm-project/commit/297ec611304663931be52e6118d9f135ceb8a027.diff

LOG: [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

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/InstCombine/phi.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 28a430e45e52..11377c467bee 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/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

diff  --git a/llvm/test/Transforms/InstCombine/phi.ll b/llvm/test/Transforms/InstCombine/phi.ll
index e61cec7da47b..b9f54862b894 100644
--- a/llvm/test/Transforms/InstCombine/phi.ll
+++ b/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) {