diff --git a/pkgs/development/compilers/llvm/3.8/D17533-1.patch b/pkgs/development/compilers/llvm/3.8/D17533-1.patch
new file mode 100644
index 00000000000..79ca953d6e5
--- /dev/null
+++ b/pkgs/development/compilers/llvm/3.8/D17533-1.patch
@@ -0,0 +1,60 @@
+commit eb92f5a745014532b83abfba04602fce87ca8393
+Author: Chuang-Yu Cheng <cycheng@multicorewareinc.com>
+Date:   Fri Apr 8 12:04:32 2016 +0000
+
+    CXX_FAST_TLS calling convention: performance improvement for PPC64
+    
+    This is the same change on PPC64 as r255821 on AArch64. I have even borrowed
+    his commit message.
+    
+    The access function has a short entry and a short exit, the initialization
+    block is only run the first time. To improve the performance, we want to
+    have a short frame at the entry and exit.
+    
+    We explicitly handle most of the CSRs via copies. Only the CSRs that are not
+    handled via copies will be in CSR_SaveList.
+    
+    Frame lowering and prologue/epilogue insertion will generate a short frame
+    in the entry and exit according to CSR_SaveList. The majority of the CSRs will
+    be handled by register allcoator. Register allocator will try to spill and
+    reload them in the initialization block.
+    
+    We add CSRsViaCopy, it will be explicitly handled during lowering.
+    
+    1> we first set FunctionLoweringInfo->SplitCSR if conditions are met (the target
+       supports it for the given machine function and the function has only return
+       exits). We also call TLI->initializeSplitCSR to perform initialization.
+    2> we call TLI->insertCopiesSplitCSR to insert copies from CSRsViaCopy to
+       virtual registers at beginning of the entry block and copies from virtual
+       registers to CSRsViaCopy at beginning of the exit blocks.
+    3> we also need to make sure the explicit copies will not be eliminated.
+    
+    Author: Tom Jablin (tjablin)
+    Reviewers: hfinkel kbarton cycheng
+    
+    http://reviews.llvm.org/D17533
+    
+    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265781 91177308-0d34-0410-b5e6-96231b3b80d8
+
+diff --git a/lib/CodeGen/TargetFrameLoweringImpl.cpp b/lib/CodeGen/TargetFrameLoweringImpl.cpp
+index 679ade1..0a0e079 100644
+--- a/lib/CodeGen/TargetFrameLoweringImpl.cpp
++++ b/lib/CodeGen/TargetFrameLoweringImpl.cpp
+@@ -63,12 +63,15 @@ void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
+   const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
+   const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF);
+ 
++  // Resize before the early returns. Some backends expect that
++  // SavedRegs.size() == TRI.getNumRegs() after this call even if there are no
++  // saved registers.
++  SavedRegs.resize(TRI.getNumRegs());
++
+   // Early exit if there are no callee saved registers.
+   if (!CSRegs || CSRegs[0] == 0)
+     return;
+ 
+-  SavedRegs.resize(TRI.getNumRegs());
+-
+   // In Naked functions we aren't going to save any registers.
+   if (MF.getFunction()->hasFnAttribute(Attribute::Naked))
+     return;