Pull in r241142 from upstream llvm trunk (by David Majnemer):

  [SCCP] Turn loads of null into undef instead of zero initialized values

  Surprisingly, this is a correctness issue: the mmx type exists for
  calling convention purposes, LLVM doesn't have a zero representation for
  them.

  This partially fixes PR23999.

Pull in r241143 from upstream llvm trunk (by David Majnemer):

  [LoopUnroll] Use undef for phis with no value live

  We would create a phi node with a zero initialized operand instead of
  undef in the case where no value was originally available.  This was
  problematic for x86_mmx which has no null value.

These fix a "Cannot create a null constant of that type!" error when
compiling the graphics/sdl2_gfx port with MMX enabled.

Introduced here: http://svnweb.freebsd.org/changeset/base/285149

Index: lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- lib/Transforms/Scalar/SCCP.cpp
+++ lib/Transforms/Scalar/SCCP.cpp
@@ -1054,7 +1054,7 @@
 
   // load null -> null
   if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0)
-    return markConstant(IV, &I, Constant::getNullValue(I.getType()));
+    return markConstant(IV, &I, UndefValue::get(I.getType()));
 
   // Transform load (constant global) into the value loaded.
   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
Index: lib/Transforms/Utils/LoopUnrollRuntime.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -81,7 +81,7 @@
       if (L->contains(PN)) {
         NewPN->addIncoming(PN->getIncomingValueForBlock(NewPH), OrigPH);
       } else {
-        NewPN->addIncoming(Constant::getNullValue(PN->getType()), OrigPH);
+        NewPN->addIncoming(UndefValue::get(PN->getType()), OrigPH);
       }
 
       Value *V = PN->getIncomingValueForBlock(Latch);
Index: test/Transforms/LoopUnroll/X86/mmx.ll
===================================================================
--- test/Transforms/LoopUnroll/X86/mmx.ll
+++ test/Transforms/LoopUnroll/X86/mmx.ll
@@ -0,0 +1,21 @@
+; RUN: opt < %s -S -loop-unroll | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define x86_mmx @f() #0 {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %phi = phi i32 [ 1, %entry ], [ %add, %for.body ]
+  %add = add i32 %phi, 1
+  %cmp = icmp eq i32 %phi, 0
+  br i1 %cmp, label %exit, label %for.body
+
+exit:                                             ; preds = %for.body
+  %ret = phi x86_mmx [ undef, %for.body ]
+  ; CHECK: ret x86_mmx %ret
+  ret x86_mmx %ret
+}
+
+attributes #0 = { "target-cpu"="x86-64" }
Index: test/Transforms/SCCP/crash.ll
===================================================================
--- test/Transforms/SCCP/crash.ll
+++ test/Transforms/SCCP/crash.ll
@@ -27,3 +27,8 @@
   %B = extractvalue [4 x i32] %A, 1
   ret i32 %B
 }
+
+define x86_mmx @test3() {
+  %load = load x86_mmx* null
+  ret x86_mmx %load
+}