From 049260d9e2f72d650d97167e1ab451384e32b014 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Tue, 1 Nov 2011 04:49:29 +0000
Subject: [PATCH] Make sure we use the right insertion point when instcombine
 replaces a PHI with another instruction.  (Specifically, don't insert an
 arbitrary instruction before a PHI.)  Fixes PR11275.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143437 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstructionCombining.cpp      |  7 +++---
 test/Transforms/InstCombine/crash.ll          | 25 +++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 288fe680971..0cc969b01de 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2028,9 +2028,10 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
         BasicBlock *InstParent = I->getParent();
         BasicBlock::iterator InsertPos = I;
 
-        if (!isa<PHINode>(Result))        // If combining a PHI, don't insert
-          while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
-            ++InsertPos;
+        // If we replace a PHI with something that isn't a PHI, fix up the
+        // insertion point.
+        if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos))
+          InsertPos = InstParent->getFirstInsertionPt();
 
         InstParent->getInstList().insert(InsertPos, Result);
 
diff --git a/test/Transforms/InstCombine/crash.ll b/test/Transforms/InstCombine/crash.ll
index 1a657f53a60..54a77aab45f 100644
--- a/test/Transforms/InstCombine/crash.ll
+++ b/test/Transforms/InstCombine/crash.ll
@@ -374,3 +374,28 @@ for.inc:                                          ; preds = %for.cond
 return:                                           ; No predecessors!
   ret void
 }
+
+; PR11275
+declare void @test18b() noreturn
+declare void @test18foo(double**)
+declare void @test18a() noreturn
+define fastcc void @test18x(i8* %t0, i1 %b) uwtable align 2 {
+entry:
+  br i1 %b, label %e1, label %e2
+e1:
+  %t2 = bitcast i8* %t0 to double**
+  invoke void @test18b() noreturn
+          to label %u unwind label %lpad
+e2:
+  %t4 = bitcast i8* %t0 to double**
+  invoke void @test18a() noreturn
+          to label %u unwind label %lpad
+lpad:
+  %t5 = phi double** [ %t2, %e1 ], [ %t4, %e2 ]
+  %lpad.nonloopexit262 = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+          cleanup
+  call void @test18foo(double** %t5)
+  unreachable
+u:
+  unreachable
+}