[llvm-bugs] [Bug 49104] New: [Attributor] Replace noundef value with undef

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49104

            Bug ID: 49104
           Summary: [Attributor] Replace noundef value with undef
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Interprocedural Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: zequanwu at google.com
                CC: llvm-bugs at lists.llvm.org

Here is the reduced IR:
target datalayout =
"e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.hash_table = type { %struct.hash_node*, i64, i64, i64 }
%struct.hash_node = type { i64, i8*, i64, i8* }
%union.label = type { %struct.anon }
%struct.anon = type { i32, i32, i64, i64, i64, i64, i8*, i8*, i8*, i8*, i32,
i32, i32 }

@ltab = external dso_local global %struct.hash_table, align 8

define hidden i32 @lookup_label() {
entry:
  br label %if.end

if.end:                                           ; preds = %entry
  %call = call %union.label* @find_label(i1 false)
  ret i32 undef
}

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #0

define internal %union.label* @find_label(i1 %create) {
entry:
  %create.addr = alloca i8, align 1
  %frombool = zext i1 %create to i8
  store i8 %frombool, i8* %create.addr, align 1
  br label %cond.true

cond.true:                                        ; preds = %entry
  br label %cond.end

cond.end:                                         ; preds = %cond.true
  br i1 undef, label %if.then, label %lor.lhs.false

lor.lhs.false:                                    ; preds = %cond.end
  %0 = load i8, i8* %create.addr, align 1, !range !0
  %tobool2 = trunc i8 %0 to i1
  br i1 %tobool2, label %if.end, label %if.then

if.then:                                          ; preds = %lor.lhs.false,
%cond.end
  ret %union.label* undef

if.end:                                           ; preds = %lor.lhs.false
  br label %if.then3

if.then3:                                         ; preds = %if.end
  %call4 = call i8* @nasm_malloc(i64 11264)
  ret %union.label* undef
}

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #0

define hidden i1 @declare_label() {
entry:
  %call = call %union.label* @find_label(i1 true)
  store %union.label* %call, %union.label** undef, align 8
  ret i1 undef
}

declare hidden i32 @init_labels()

declare i8* @nasm_malloc(i64)

declare dso_local void @init_block()

; Function Attrs: argmemonly nofree nosync nounwind willreturn writeonly
declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg)
#1

declare i8** @hash_find()

; Function Attrs: argmemonly nofree nosync nounwind willreturn
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8*
noalias nocapture readonly, i64, i1 immarg) #0

attributes #0 = { argmemonly nofree nosync nounwind willreturn }
attributes #1 = { argmemonly nofree nosync nounwind willreturn writeonly }

!0 = !{i8 0, i8 2}


commands:
opt -O2 --attributor-enable=cgscc reduced.ll

Debug dumpping shows:
[Attributor] Delete at least 0 functions and 0 blocks and 0 instructions and 2
uses
Use i1 undef in   call fastcc void @find_label(i1 noundef true) instead of i1
true
Use i1 true in   br i1 %create, label %if.then3, label %if.then instead of i1
%create

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