Add support to ADCE for pruning unreachable blocks. This addresses the final

part of PR2509.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53038 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/ADCE/2008-07-02-Unreachable.ll

@@ -0,0 +1,37 @@
+; RUN: llvm-as < %s | opt -adce -simplifycfg | llvm-dis | not grep forcond
+; PR2509
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i686-apple-darwin9.3.0"
+@g_3 = external global i8		; <i8*> [#uses=2]
+
+define i32 @func_1() nounwind  {
+entry:
+	br i1 false, label %ifelse, label %ifthen
+
+ifthen:		; preds = %entry
+	br label %ifend
+
+ifelse:		; preds = %entry
+	%tmp3 = load i8* @g_3		; <i8> [#uses=0]
+	br label %forcond.thread
+
+forcond.thread:		; preds = %ifelse
+	br label %afterfor
+
+forcond:		; preds = %forinc
+	br i1 false, label %afterfor, label %forbody
+
+forbody:		; preds = %forcond
+	br label %forinc
+
+forinc:		; preds = %forbody
+	br label %forcond
+
+afterfor:		; preds = %forcond, %forcond.thread
+	%tmp10 = load i8* @g_3		; <i8> [#uses=0]
+	br label %ifend
+
+ifend:		; preds = %afterfor, %ifthen
+	ret i32 0
+}