[ValueLattice] Reset the count of range extensions when merging an undef with a constant range.

llvm/include/llvm/Analysis/ValueLattice.h

@@ -406,6 +406,7 @@ class ValueLatticeElement {
     if (isUnknown()) {
       assert(!RHS.isUnknown() && "Unknow RHS should be handled earlier");
       *this = RHS;
+      NumRangeExtensions = 0;
       return true;
     }
 

llvm/test/Transforms/SCCP/widen-steps-limit.ll

@@ -0,0 +1,91 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S -passes=sccp < %s | FileCheck %s
+
+define void @test() {
+; CHECK-LABEL: define void @test() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call i8 @geti8()
+; CHECK-NEXT:    [[CONV_I:%.*]] = zext i8 [[TMP0]] to i32
+; CHECK-NEXT:    [[CMP19_I_NOT:%.*]] = tail call i1 @geti1()
+; CHECK-NEXT:    br i1 [[CMP19_I_NOT]], label [[WHILE_END_I_THREAD:%.*]], label [[EXIT2:%.*]]
+; CHECK:       while.end.i.thread:
+; CHECK-NEXT:    [[TMP1:%.*]] = tail call i1 @geti1()
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i1 [[TMP1]] to i32
+; CHECK-NEXT:    br label [[EXIT2]]
+; CHECK:       exit2:
+; CHECK-NEXT:    [[CMP_I12_I4:%.*]] = phi i32 [ [[TMP2]], [[WHILE_END_I_THREAD]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = tail call i1 @geti1()
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN6:%.*]], label [[IF_END_I_I:%.*]]
+; CHECK:       if.then6:
+; CHECK-NEXT:    [[CMP_I32:%.*]] = icmp ugt i32 [[CMP_I12_I4]], [[CONV_I]]
+; CHECK-NEXT:    br i1 [[CMP_I32]], label [[EXIT:%.*]], label [[COND_FALSE_I:%.*]]
+; CHECK:       cond.false.i:
+; CHECK-NEXT:    [[CMP_NOT6_I_I:%.*]] = tail call i1 @geti1()
+; CHECK-NEXT:    br i1 [[CMP_NOT6_I_I]], label [[EXIT]], label [[FOR_BODY_PREHEADER_I_I:%.*]]
+; CHECK:       for.body.preheader.i.i:
+; CHECK-NEXT:    [[CMP_NOT_I_I:%.*]] = tail call i1 @geti1()
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RETVAL_SROA_3_0_I:%.*]] = phi i32 [ 0, [[IF_THEN6]] ], [ 1, [[COND_FALSE_I]] ], [ 1, [[FOR_BODY_PREHEADER_I_I]] ]
+; CHECK-NEXT:    br i1 [[CMP19_I_NOT]], label [[IF_END_I_I]], label [[DO_BODY_I_I:%.*]]
+; CHECK:       do.body.i.i:
+; CHECK-NEXT:    br label [[IF_END_I_I]]
+; CHECK:       if.end.i.i:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = tail call i8 @geti8()
+  %conv.i = zext i8 %0 to i32
+  %cmp19.i.not = tail call i1 @geti1()
+  br i1 %cmp19.i.not, label %while.end.i.thread, label %exit2
+
+while.end.i.thread:                               ; preds = %entry
+  %1 = tail call i1 @geti1()
+  %2 = zext i1 %1 to i32
+  br label %exit2
+
+exit2:                                            ; preds = %while.end.i.thread, %entry
+  %cmp.i12.i4 = phi i32 [ %2, %while.end.i.thread ], [ 0, %entry ]
+  %cmp = tail call i1 @geti1()
+  br i1 %cmp, label %if.then6, label %if.end.i.i
+
+if.then6:                                         ; preds = %exit2
+  %cmp.i32 = icmp ugt i32 %cmp.i12.i4, %conv.i
+  br i1 %cmp.i32, label %exit, label %cond.false.i
+
+cond.false.i:                                     ; preds = %if.then6
+  %cmp.not6.i.i = tail call i1 @geti1()
+  br i1 %cmp.not6.i.i, label %exit, label %for.body.preheader.i.i
+
+for.body.preheader.i.i:                           ; preds = %cond.false.i
+  %cmp.not.i.i = tail call i1 @geti1()
+  br label %exit
+
+exit:                                             ; preds = %for.body.preheader.i.i, %cond.false.i, %if.then6
+  %retval.sroa.3.0.i = phi i32 [ 0, %if.then6 ], [ 1, %cond.false.i ], [ 1, %for.body.preheader.i.i ]
+  br i1 %cmp19.i.not, label %if.end.i.i, label %do.body.i.i
+
+do.body.i.i:                                      ; preds = %exit, %do.cond.i.i
+  %result.sroa.7.0.i.i = phi i32 [ %result.sroa.7.1.i.i, %do.cond.i.i ], [ %retval.sroa.3.0.i, %exit ]
+  switch i32 %result.sroa.7.0.i.i, label %do.cond.i.i [
+  i32 2, label %sw.bb.i.i
+  i32 1, label %if.end.i.i
+  i32 0, label %if.end.i.i
+  ]
+
+sw.bb.i.i:                                        ; preds = %do.body.i.i
+  %3 = tail call i32 @geti32()
+  br label %do.cond.i.i
+
+do.cond.i.i:                                      ; preds = %sw.bb.i.i, %do.body.i.i
+  %result.sroa.7.1.i.i = phi i32 [ %result.sroa.7.0.i.i, %do.body.i.i ], [ %3, %sw.bb.i.i ]
+  %cmp22.i.i = tail call i1 @geti1()
+  br i1 %cmp22.i.i, label %do.body.i.i, label %if.end.i.i
+
+if.end.i.i:                                       ; preds = %do.cond.i.i, %do.body.i.i, %do.body.i.i, %exit, %exit2
+  ret void
+}
+
+declare i8 @geti8()
+declare i32 @geti32()
+declare i1 @geti1()