From 0041d4d447c26825e566ba38a4fe301471fda1eb Mon Sep 17 00:00:00 2001
From: Andrew Trick <atrick@apple.com>
Date: Fri, 20 Jan 2012 21:23:40 +0000
Subject: [PATCH] Handle a corner case with IV chain collection with bailout
 instead of assert.

Fixes PR11783: bad cast to AddRecExpr.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148572 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopStrengthReduce.cpp  |  8 +++-
 test/Transforms/LoopStrengthReduce/ivchain.ll | 43 +++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 test/Transforms/LoopStrengthReduce/ivchain.ll

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 42f45ae6273..5aee483332a 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2484,11 +2484,15 @@ void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
       DEBUG(dbgs() << "IV Chain Limit\n");
       return;
     }
+    LastIncExpr = SE.getSCEV(NextIV);
+    // IVUsers may have skipped over sign/zero extensions. We don't currently
+    // attempt to form chains involving extensions unless they can be hoisted
+    // into this loop's AddRec.
+    if (!isa<SCEVAddRecExpr>(LastIncExpr))
+      return;
     ++NChains;
     IVChainVec.resize(NChains);
     ChainUsersVec.resize(NChains);
-    LastIncExpr = SE.getSCEV(NextIV);
-    assert(isa<SCEVAddRecExpr>(LastIncExpr) && "expect recurrence at IV user");
     DEBUG(dbgs() << "IV Head: (" << *UserInst << ") IV=" << *LastIncExpr
           << "\n");
   }
diff --git a/test/Transforms/LoopStrengthReduce/ivchain.ll b/test/Transforms/LoopStrengthReduce/ivchain.ll
new file mode 100644
index 00000000000..ce7ad198de4
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/ivchain.ll
@@ -0,0 +1,43 @@
+; RUN: opt < %s -loop-reduce -S | FileCheck %s
+;
+; PR11782: bad cast to AddRecExpr.
+; A sign extend feeds an IVUser and cannot be hoisted into the AddRec.
+; CollectIVChains should bailout on this case.
+
+%struct = type { i8*, i8*, i16, i64, i16, i16, i16, i64, i64, i16, i8*, i64, i64, i64 }
+
+; CHECK: @test
+; CHECK: for.body:
+; CHECK: lsr.iv = phi %struct
+; CHECK: br
+define i32 @test(i8* %h, i32 %more) nounwind uwtable {
+entry:
+  br i1 undef, label %land.end238, label %return
+
+land.end238:                                      ; preds = %if.end229
+  br label %for.body
+
+for.body:                                         ; preds = %sw.epilog, %land.end238
+  %fbh.0 = phi %struct* [ undef, %land.end238 ], [ %incdec.ptr, %sw.epilog ]
+  %column_n.0 = phi i16 [ 0, %land.end238 ], [ %inc601, %sw.epilog ]
+  %conv250 = sext i16 %column_n.0 to i32
+  %add257 = add nsw i32 %conv250, 1
+  %conv258 = trunc i32 %add257 to i16
+  %cmp263 = icmp ult i16 undef, 2
+  br label %if.end388
+
+if.end388:                                        ; preds = %if.then380, %if.else356
+  %ColLength = getelementptr inbounds %struct* %fbh.0, i64 0, i32 7
+  %call405 = call signext i16 @SQLColAttribute(i8* undef, i16 zeroext %conv258, i16 zeroext 1003, i8* null, i16 signext 0, i16* null, i64* %ColLength) nounwind
+  br label %sw.epilog
+
+sw.epilog:                                        ; preds = %sw.bb542, %sw.bb523, %if.end475
+  %inc601 = add i16 %column_n.0, 1
+  %incdec.ptr = getelementptr inbounds %struct* %fbh.0, i64 1
+  br label %for.body
+
+return:                                           ; preds = %entry
+  ret i32 1
+}
+
+declare signext i16 @SQLColAttribute(i8*, i16 zeroext, i16 zeroext, i8*, i16 signext, i16*, i64*)