From 482eb70a10b831d449bdff5565355309f5861f10 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 9 Jan 2009 06:08:12 +0000
Subject: [PATCH] Fix PR3298, a crash in Jump Threading.  Apparently even jump
 threading can have bugs, who knew? ;-)

llvm-svn: 61983
---
 llvm/lib/Transforms/Scalar/JumpThreading.cpp  |  4 ++
 .../JumpThreading/2009-01-08-DeadLoopRepl.ll  | 49 +++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 llvm/test/Transforms/JumpThreading/2009-01-08-DeadLoopRepl.ll

diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 59af14b86556..94d33aa78794 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -504,6 +504,10 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
     // If the value if the load is locally available within the block, just use
     // it.  This frequently occurs for reg2mem'd allocas.
     //cerr << "LOAD ELIMINATED:\n" << *BBIt << *LI << "\n";
+    
+    // If the returned value is the load itself, replace with an undef. This can
+    // only happen in dead loops.
+    if (AvailableVal == LI) AvailableVal = UndefValue::get(LI->getType());
     LI->replaceAllUsesWith(AvailableVal);
     LI->eraseFromParent();
     return true;
diff --git a/llvm/test/Transforms/JumpThreading/2009-01-08-DeadLoopRepl.ll b/llvm/test/Transforms/JumpThreading/2009-01-08-DeadLoopRepl.ll
new file mode 100644
index 000000000000..6de67ebbcecc
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/2009-01-08-DeadLoopRepl.ll
@@ -0,0 +1,49 @@
+; RUN: llvm-as < %s | opt -jump-threading | llvm-dis
+; PR3298
+
+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 = "i386-apple-darwin9.6"
+
+define i32 @func(i32 %p_79, i32 %p_80) nounwind {
+entry:
+	br label %bb7
+
+bb1:		; preds = %bb2
+	br label %bb2
+
+bb2:		; preds = %bb7, %bb1
+	%l_82.0 = phi i8 [ 0, %bb1 ], [ %l_82.1, %bb7 ]		; <i8> [#uses=3]
+	br i1 true, label %bb3, label %bb1
+
+bb3:		; preds = %bb2
+	%0 = icmp eq i32 %p_80_addr.1, 0		; <i1> [#uses=1]
+	br i1 %0, label %bb7, label %bb6
+
+bb5:		; preds = %bb6
+	%1 = icmp eq i8 %l_82.0, 0		; <i1> [#uses=1]
+	br i1 %1, label %bb1.i, label %bb.i
+
+bb.i:		; preds = %bb5
+	br label %safe_div_func_char_s_s.exit
+
+bb1.i:		; preds = %bb5
+	br label %safe_div_func_char_s_s.exit
+
+safe_div_func_char_s_s.exit:		; preds = %bb1.i, %bb.i
+	br label %bb6
+
+bb6:		; preds = %safe_div_func_char_s_s.exit, %bb3
+	%p_80_addr.0 = phi i32 [ %p_80_addr.1, %bb3 ], [ 1, %safe_div_func_char_s_s.exit ]		; <i32> [#uses=2]
+	%2 = icmp eq i32 %p_80_addr.0, 0		; <i1> [#uses=1]
+	br i1 %2, label %bb7, label %bb5
+
+bb7:		; preds = %bb6, %bb3, %entry
+	%l_82.1 = phi i8 [ 1, %entry ], [ %l_82.0, %bb3 ], [ %l_82.0, %bb6 ]		; <i8> [#uses=2]
+	%p_80_addr.1 = phi i32 [ 0, %entry ], [ %p_80_addr.1, %bb3 ], [ %p_80_addr.0, %bb6 ]		; <i32> [#uses=4]
+	%3 = icmp eq i32 %p_80_addr.1, 0		; <i1> [#uses=1]
+	br i1 %3, label %bb8, label %bb2
+
+bb8:		; preds = %bb7
+	%4 = sext i8 %l_82.1 to i32		; <i32> [#uses=0]
+	ret i32 0
+}