From de2e27cc52a9e47e0261dda6dfb54a32eefa90a0 Mon Sep 17 00:00:00 2001
From: Pete Cooper <peter_cooper@apple.com>
Date: Sat, 3 Dec 2011 00:04:30 +0000
Subject: [PATCH] Fixed deadstoreelimination bug where negative indices were
 incorrectly causing the optimisation to occur

Turns out long long + unsigned long long is unsigned.  Doh!

Fixes http://llvm.org/bugs/show_bug.cgi?id=11455

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145731 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/DeadStoreElimination.cpp  |  2 +-
 .../DeadStoreElimination/OverwriteStoreEnd.ll   | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index f5688cb3b4a..b9b1cc86c29 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -416,7 +416,7 @@ static OverwriteResult isOverwrite(const AliasAnalysis::Location &Later,
   // writes to addresses which will definitely be overwritten later
   if (LaterOff > EarlierOff &&
       LaterOff < int64_t(EarlierOff + Earlier.Size) &&
-      LaterOff + Later.Size >= EarlierOff + Earlier.Size)
+      int64_t(LaterOff + Later.Size) >= int64_t(EarlierOff + Earlier.Size))
     return OverwriteEnd;
 
   // Otherwise, they don't completely overlap.
diff --git a/test/Transforms/DeadStoreElimination/OverwriteStoreEnd.ll b/test/Transforms/DeadStoreElimination/OverwriteStoreEnd.ll
index 828ccc57a44..ed53eb524c2 100644
--- a/test/Transforms/DeadStoreElimination/OverwriteStoreEnd.ll
+++ b/test/Transforms/DeadStoreElimination/OverwriteStoreEnd.ll
@@ -76,3 +76,20 @@ entry:
 
 declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
 declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
+
+%struct.trapframe = type { i64, i64, i64 }
+
+; bugzilla 11455 - make sure negative GEP's don't break this optimisation
+; CHECK: @cpu_lwp_fork
+define void @cpu_lwp_fork(%struct.trapframe* %md_regs, i64 %pcb_rsp0) nounwind uwtable noinline ssp {
+entry:
+  %0 = inttoptr i64 %pcb_rsp0 to %struct.trapframe*
+  %add.ptr = getelementptr inbounds %struct.trapframe* %0, i64 -1
+  %1 = bitcast %struct.trapframe* %add.ptr to i8*
+  %2 = bitcast %struct.trapframe* %md_regs to i8*
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %1, i8* %2, i64 24, i32 1, i1 false)
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %1, i8* %2, i64 24, i32 1, i1 false)
+  %tf_trapno = getelementptr inbounds %struct.trapframe* %0, i64 -1, i32 1
+  store i64 3, i64* %tf_trapno, align 8
+  ret void
+}