[ValueTracking] Skip incoming values that are the same as the phi in isGuaranteedNotToBeUndefOrPoison

llvm/lib/Analysis/ValueTracking.cpp

@@ -7824,6 +7824,8 @@ static bool isGuaranteedNotToBeUndefOrPoison(
       unsigned Num = PN->getNumIncomingValues();
       bool IsWellDefined = true;
       for (unsigned i = 0; i < Num; ++i) {
+        if (PN == PN->getIncomingValue(i))
+          continue;
         auto *TI = PN->getIncomingBlock(i)->getTerminator();
         if (!isGuaranteedNotToBeUndefOrPoison(PN->getIncomingValue(i), AC, TI,
                                               DT, Depth + 1, Kind)) {

llvm/test/Analysis/ValueTracking/phi-self.ll

@@ -0,0 +1,145 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instsimplify < %s | FileCheck %s
+
+; Test `%r` can be replaced by `%nonpoison`.
+
+define i64 @other_noundef() {
+; CHECK-LABEL: define i64 @other_noundef() {
+; CHECK-NEXT:  [[START:.*]]:
+; CHECK-NEXT:    br label %[[LOOP:.*]]
+; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[R:%.*]] = phi i64 [ [[R]], %[[BB0:.*]] ], [ [[R]], %[[BB1:.*]] ], [ [[R]], %[[BB2:.*]] ], [ [[R]], %[[BB:.*]] ], [ [[I:%.*]], %[[BACK_TO_LOOP:.*]] ], [ 0, %[[START]] ]
+; CHECK-NEXT:    [[I]] = call i64 @opaque()
+; CHECK-NEXT:    switch i64 [[I]], label %[[EXIT0:.*]] [
+; CHECK-NEXT:      i64 -1, label %[[EXIT1:.*]]
+; CHECK-NEXT:      i64 2, label %[[BACK_TO_LOOP]]
+; CHECK-NEXT:      i64 0, label %[[BB]]
+; CHECK-NEXT:    ]
+; CHECK:       [[EXIT0]]:
+; CHECK-NEXT:    br label %[[EXIT1]]
+; CHECK:       [[EXIT1]]:
+; CHECK-NEXT:    ret i64 [[R]]
+; CHECK:       [[BACK_TO_LOOP]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[BB]]:
+; CHECK-NEXT:    switch i64 [[R]], label %[[LOOP]] [
+; CHECK-NEXT:      i64 0, label %[[BB0]]
+; CHECK-NEXT:      i64 1, label %[[BB1]]
+; CHECK-NEXT:      i64 2, label %[[BB2]]
+; CHECK-NEXT:    ]
+; CHECK:       [[BB0]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[BB1]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[BB2]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+;
+start:
+  br label %loop
+
+loop:                                             ; preds = %bb2, %bb1, %bb0, %bb, %back_to_loop, %start
+  %nonpoison = phi i64 [ %nonpoison, %bb0 ], [ %nonpoison, %bb1 ], [ %nonpoison, %bb2 ], [ %nonpoison, %bb ], [ %i, %back_to_loop ], [ 0, %start ]
+  %i = call i64 @opaque()
+  switch i64 %i, label %exit0 [
+  i64 -1, label %exit1
+  i64 2, label %back_to_loop
+  i64 0, label %bb
+  ]
+
+exit0:                                            ; preds = %loop
+  br label %exit1
+
+exit1:                                            ; preds = %exit0, %loop
+  %r = phi i64 [ %nonpoison, %loop ], [ undef, %exit0 ]
+  ret i64 %r
+
+back_to_loop:                                     ; preds = %loop
+  br label %loop
+
+bb:                                               ; preds = %loop
+  switch i64 %nonpoison, label %loop [
+  i64 0, label %bb0
+  i64 1, label %bb1
+  i64 2, label %bb2
+  ]
+
+bb0:                                              ; preds = %bb
+  br label %loop
+
+bb1:                                              ; preds = %bb
+  br label %loop
+
+bb2:                                              ; preds = %bb
+  br label %loop
+}
+
+define i64 @other_poison() {
+; CHECK-LABEL: define i64 @other_poison() {
+; CHECK-NEXT:  [[START:.*:]]
+; CHECK-NEXT:    br label %[[LOOP:.*]]
+; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[I:%.*]] = call i64 @opaque()
+; CHECK-NEXT:    switch i64 [[I]], label %[[EXIT0:.*]] [
+; CHECK-NEXT:      i64 -1, label %[[EXIT1:.*]]
+; CHECK-NEXT:      i64 2, label %[[BACK_TO_LOOP:.*]]
+; CHECK-NEXT:      i64 0, label %[[BB:.*]]
+; CHECK-NEXT:    ]
+; CHECK:       [[EXIT0]]:
+; CHECK-NEXT:    br label %[[EXIT1]]
+; CHECK:       [[EXIT1]]:
+; CHECK-NEXT:    ret i64 0
+; CHECK:       [[BACK_TO_LOOP]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[BB]]:
+; CHECK-NEXT:    switch i64 0, label %[[LOOP]] [
+; CHECK-NEXT:      i64 0, label %[[BB0:.*]]
+; CHECK-NEXT:      i64 1, label %[[BB1:.*]]
+; CHECK-NEXT:      i64 2, label %[[BB2:.*]]
+; CHECK-NEXT:    ]
+; CHECK:       [[BB0]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[BB1]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[BB2]]:
+; CHECK-NEXT:    br label %[[LOOP]]
+;
+start:
+  br label %loop
+
+loop:                                             ; preds = %bb2, %bb1, %bb0, %bb, %back_to_loop, %start
+  %maypoison = phi i64 [ %maypoison, %bb0 ], [ %maypoison, %bb1 ], [ %maypoison, %bb2 ], [ %maypoison, %bb ], [ poison, %back_to_loop ], [ 0, %start ]
+  %i = call i64 @opaque()
+  switch i64 %i, label %exit0 [
+  i64 -1, label %exit1
+  i64 2, label %back_to_loop
+  i64 0, label %bb
+  ]
+
+exit0:                                            ; preds = %loop
+  br label %exit1
+
+exit1:                                            ; preds = %exit0, %loop
+  %r = phi i64 [ %maypoison, %loop ], [ undef, %exit0 ]
+  ret i64 %r
+
+back_to_loop:                                     ; preds = %loop
+  br label %loop
+
+bb:                                               ; preds = %loop
+  switch i64 %maypoison, label %loop [
+  i64 0, label %bb0
+  i64 1, label %bb1
+  i64 2, label %bb2
+  ]
+
+bb0:                                              ; preds = %bb
+  br label %loop
+
+bb1:                                              ; preds = %bb
+  br label %loop
+
+bb2:                                              ; preds = %bb
+  br label %loop
+}
+
+declare i64 @opaque()