Replace branches with poison

This test is a crash test, which generates different code for
well defined-branches. The original approach with replacing undef with
a new function argument may break some tests coverage. However, LLVM
will not support undef in the long run. Thus, we replaced
the original undef branches with poison, so that we remove undef and
also keep the test coverage.

Author: leewei05

llvm/test/DebugInfo/X86/earlydup-crash.ll

@@ -6,15 +6,15 @@
 
 declare void @llvm.dbg.value(metadata, metadata, metadata) nounwind readnone
 
-define internal ptr @framework_construct_pathname(ptr %fname, ptr %dir, i1 %arg) nounwind ssp !dbg !2 {
+define internal ptr @framework_construct_pathname(ptr %fname, ptr %dir) nounwind ssp !dbg !2 {
 entry:
-  br i1 %arg, label %bb33, label %bb
+  br i1 poison, label %bb33, label %bb
 
 bb:                                               ; preds = %entry
   %tmp = icmp eq i32 undef, 0
   %tmp1 = add i32 0, 11
   call void @llvm.dbg.value(metadata i32 %tmp1, metadata !0, metadata !DIExpression()), !dbg !DILocation(scope: !1)
-  br i1 %arg, label %bb18, label %bb31.preheader
+  br i1 poison, label %bb18, label %bb31.preheader
 
 bb31.preheader:                                   ; preds = %bb19, %bb
   br label %bb31
@@ -30,7 +30,7 @@ bb19:                                             ; preds = %bb18
 bb22:                                             ; preds = %bb31
   %tmp4 = add i32 0, %tmp1
   call void @foobar(i32 %tmp4)
-  br i1 %arg, label %bb33, label %bb31
+  br i1 poison, label %bb33, label %bb31
 
 bb31:                                             ; preds = %bb22, %bb31.preheader
   br i1 false, label %bb33, label %bb22