diff --git a/debian/changelog b/debian/changelog
index a6208e34..eec039c8 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -5,8 +5,10 @@ llvm-toolchain-6.0 (1:6.0.1-7) unstable; urgency=medium
     See upstream bug 38663
   * Fix an alignment issue
     See upstream bug 38707 (Closes: #907622)
+  * Fix an optimization issues (Closes: #907649)
+    See upstream bug 38786
 
- --
+ -- Sylvestre Ledru <sylvestre@debian.org>  Thu, 06 Sep 2018 20:51:24 +0200
 
 llvm-toolchain-6.0 (1:6.0.1-6) unstable; urgency=medium
 
diff --git a/debian/patches/D51639-optim-issue.diff b/debian/patches/D51639-optim-issue.diff
new file mode 100644
index 00000000..791ef595
--- /dev/null
+++ b/debian/patches/D51639-optim-issue.diff
@@ -0,0 +1,46 @@
+Index: llvm-toolchain-6.0-6.0.1/lib/Transforms/Vectorize/LoopVectorize.cpp
+===================================================================
+--- llvm-toolchain-6.0-6.0.1.orig/lib/Transforms/Vectorize/LoopVectorize.cpp
++++ llvm-toolchain-6.0-6.0.1/lib/Transforms/Vectorize/LoopVectorize.cpp
+@@ -4529,6 +4529,11 @@
+       // isOutOfScope operands cannot be uniform instructions.
+       if (isOutOfScope(OV))
+         continue;
++      // First order recurrence Phi's should typically be considered
++      // non-uniform.
++      auto *OP = dyn_cast<PHINode>(OV);
++      if (OP && Legal->isFirstOrderRecurrence(OP))
++        continue;
+       // If all the users of the operand are uniform, then add the
+       // operand into the uniform worklist.
+       auto *OI = cast<Instruction>(OV);
+Index: llvm-toolchain-6.0-6.0.1/test/Transforms/LoopVectorize/X86/uniform-phi.ll
+===================================================================
+--- llvm-toolchain-6.0-6.0.1.orig/test/Transforms/LoopVectorize/X86/uniform-phi.ll
++++ llvm-toolchain-6.0-6.0.1/test/Transforms/LoopVectorize/X86/uniform-phi.ll
+@@ -75,3 +75,25 @@
+   ret i64 %retval
+ }
+ 
++; CHECK-LABEL: PR38786
++; Check that first order recurrence phis (%phi32 and %phi64) are not uniform.
++; CHECK-NOT: LV: Found uniform instruction:   %phi
++define void @PR38786(double* %y, double* %x, i64 %n) {
++entry:
++  br label %for.body
++
++for.body:
++  %phi32 = phi i32 [ 0, %entry ], [ %i32next, %for.body ]
++  %phi64 = phi i64 [ 0, %entry ], [ %i64next, %for.body ]
++  %i32next = add i32 %phi32, 1
++  %i64next = zext i32 %i32next to i64
++  %xip = getelementptr inbounds double, double* %x, i64 %i64next
++  %yip = getelementptr inbounds double, double* %y, i64 %phi64
++  %xi = load double, double* %xip, align 8
++  store double %xi, double* %yip, align 8
++  %cmp = icmp slt i64 %i64next, %n
++  br i1 %cmp, label %for.body, label %for.end
++
++for.end:
++  ret void
++}
diff --git a/debian/patches/series b/debian/patches/series
index 5cdd2645..0e732a84 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -63,3 +63,4 @@ PowerPC-Make-AddrSpaceCast-noop.diff
 D51108-rust-powerpc.diff
 pr38663-pgo-lto-crash.patch
 D51335-alignment-issue.diff
+D51639-optim-issue.diff