Do not pass an invalid domtree to SimplifyInstruction from

LoopUnswitch.  Fixes PR12887.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157140 91177308-0d34-0410-b5e6-96231b3b80d8

Author: pcc

lib/Transforms/Scalar/LoopUnswitch.cpp

@@ -1214,8 +1214,8 @@ void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L) {
 
     // See if instruction simplification can hack this up.  This is common for
     // things like "select false, X, Y" after unswitching made the condition be
-    // 'false'.
-    if (Value *V = SimplifyInstruction(I, 0, 0, DT))
+    // 'false'.  TODO: update the domtree properly so we can pass it here.
+    if (Value *V = SimplifyInstruction(I))
       if (LI->replacementPreservesLCSSAForm(I, V)) {
         ReplaceUsesOfWith(I, V, Worklist, L, LPM);
         continue;

test/Transforms/LoopUnswitch/2012-05-20-Phi.ll

@@ -0,0 +1,25 @@
+; RUN: opt < %s -loop-unswitch -disable-output
+; PR12887
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@a = common global i32 0, align 4
+@c = common global i32 0, align 4
+@b = common global i32 0, align 4
+
+define void @func() noreturn nounwind uwtable {
+entry:
+  %0 = load i32* @a, align 4
+  %tobool = icmp eq i32 %0, 0
+  %1 = load i32* @b, align 4
+  br label %while.body
+
+while.body:                                       ; preds = %while.body, %entry
+  %d.0 = phi i8 [ undef, %entry ], [ %conv2, %while.body ]
+  %conv = sext i8 %d.0 to i32
+  %cond = select i1 %tobool, i32 0, i32 %conv
+  %conv11 = zext i8 %d.0 to i32
+  %add = add i32 %1, %conv11
+  %conv2 = trunc i32 %add to i8
+  br label %while.body
+}