diff --git a/lib/Target/X86/X86Instr64bit.td b/lib/Target/X86/X86Instr64bit.td
index b67cb630bbe..6bfa9a6949b 100644
--- a/lib/Target/X86/X86Instr64bit.td
+++ b/lib/Target/X86/X86Instr64bit.td
@@ -1106,13 +1106,13 @@ def OR64rm   : RI<0x0B, MRMSrcMem , (outs GR64:$dst),
 def OR64ri8  : RIi8<0x83, MRM1r, (outs GR64:$dst),
                     (ins GR64:$src1, i64i8imm:$src2),
                     "or{q}\t{$src2, $dst|$dst, $src2}",
-                    [(set GR64:$dst, (or GR64:$src1, i64immSExt8:$src2)),
-                     (implicit EFLAGS)]>;
+                   [(set GR64:$dst, (or_not_add GR64:$src1, i64immSExt8:$src2)),
+                    (implicit EFLAGS)]>;
 def OR64ri32 : RIi32<0x81, MRM1r, (outs GR64:$dst),
                      (ins GR64:$src1, i64i32imm:$src2),
                      "or{q}\t{$src2, $dst|$dst, $src2}",
-                     [(set GR64:$dst, (or GR64:$src1, i64immSExt32:$src2)),
-                      (implicit EFLAGS)]>;
+                  [(set GR64:$dst, (or_not_add GR64:$src1, i64immSExt32:$src2)),
+                    (implicit EFLAGS)]>;
 } // isTwoAddress
 
 def OR64mr : RI<0x09, MRMDestMem, (outs), (ins i64mem:$dst, GR64:$src),
@@ -2114,6 +2114,14 @@ def : Pat<(store (shld (loadi64 addr:$dst), (i8 imm:$amt1),
                        GR64:$src2, (i8 imm:$amt2)), addr:$dst),
           (SHLD64mri8 addr:$dst, GR64:$src2, (i8 imm:$amt1))>;
 
+// (or x, c) -> (add x, c) if masked bits are known zero.
+def : Pat<(parallel (or_is_add GR64:$src1, i64immSExt8:$src2),
+                    (implicit EFLAGS)),
+          (ADD64ri8 GR64:$src1, i64immSExt8:$src2)>;
+def : Pat<(parallel (or_is_add GR64:$src1, i64immSExt32:$src2),
+                    (implicit EFLAGS)),
+          (ADD64ri32 GR64:$src1, i64immSExt32:$src2)>;
+
 // X86 specific add which produces a flag.
 def : Pat<(addc GR64:$src1, GR64:$src2),
           (ADD64rr GR64:$src1, GR64:$src2)>;
diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 3323e23ef8c..6835176485a 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -493,6 +493,18 @@ def trunc_su : PatFrag<(ops node:$src), (trunc node:$src), [{
   return N->hasOneUse();
 }]>;
 
+// Treat an 'or' node is as an 'add' if the or'ed bits are known to be zero.
+def or_is_add : PatFrag<(ops node:$lhs, node:$rhs), (or node:$lhs, node:$rhs),[{
+  if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N->getOperand(1)))
+    return CurDAG->MaskedValueIsZero(N->getOperand(0), CN->getAPIntValue());
+  return false;
+}]>;
+def or_not_add : PatFrag<(ops node:$lhs, node:$rhs),(or node:$lhs, node:$rhs),[{
+  ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N->getOperand(1));
+  if (!CN) return true;
+  return !CurDAG->MaskedValueIsZero(N->getOperand(0), CN->getAPIntValue());
+}]>;
+
 // 'shld' and 'shrd' instruction patterns. Note that even though these have
 // the srl and shl in their patterns, the C++ code must still check for them,
 // because predicates are tested before children nodes are explored.
@@ -1880,28 +1892,28 @@ def OR32rm   : I<0x0B, MRMSrcMem , (outs GR32:$dst),
 def OR8ri    : Ii8 <0x80, MRM1r, (outs GR8 :$dst), 
                     (ins GR8 :$src1, i8imm:$src2),
                     "or{b}\t{$src2, $dst|$dst, $src2}",
-                    [(set GR8:$dst, (or GR8:$src1, imm:$src2)),
+                    [(set GR8:$dst, (or_not_add GR8:$src1, imm:$src2)),
                      (implicit EFLAGS)]>;
 def OR16ri   : Ii16<0x81, MRM1r, (outs GR16:$dst), 
                     (ins GR16:$src1, i16imm:$src2),
                     "or{w}\t{$src2, $dst|$dst, $src2}", 
-                    [(set GR16:$dst, (or GR16:$src1, imm:$src2)),
+                    [(set GR16:$dst, (or_not_add GR16:$src1, imm:$src2)),
                      (implicit EFLAGS)]>, OpSize;
 def OR32ri   : Ii32<0x81, MRM1r, (outs GR32:$dst), 
                     (ins GR32:$src1, i32imm:$src2),
                     "or{l}\t{$src2, $dst|$dst, $src2}",
-                    [(set GR32:$dst, (or GR32:$src1, imm:$src2)),
+                    [(set GR32:$dst, (or_not_add GR32:$src1, imm:$src2)),
                      (implicit EFLAGS)]>;
 
 def OR16ri8  : Ii8<0x83, MRM1r, (outs GR16:$dst), 
                    (ins GR16:$src1, i16i8imm:$src2),
                    "or{w}\t{$src2, $dst|$dst, $src2}",
-                   [(set GR16:$dst, (or GR16:$src1, i16immSExt8:$src2)),
+                   [(set GR16:$dst, (or_not_add GR16:$src1, i16immSExt8:$src2)),
                     (implicit EFLAGS)]>, OpSize;
 def OR32ri8  : Ii8<0x83, MRM1r, (outs GR32:$dst), 
                    (ins GR32:$src1, i32i8imm:$src2),
                    "or{l}\t{$src2, $dst|$dst, $src2}",
-                   [(set GR32:$dst, (or GR32:$src1, i32immSExt8:$src2)),
+                   [(set GR32:$dst, (or_not_add GR32:$src1, i32immSExt8:$src2)),
                     (implicit EFLAGS)]>;
 let isTwoAddress = 0 in {
   def OR8mr  : I<0x08, MRMDestMem, (outs), (ins i8mem:$dst, GR8:$src),
@@ -4647,6 +4659,23 @@ def : Pat<(i16 (anyext (i8 (X86setcc_c X86_COND_B, EFLAGS)))),
 def : Pat<(i32 (anyext (i8 (X86setcc_c X86_COND_B, EFLAGS)))),
           (SETB_C32r)>;
 
+// (or x, c) -> (add x, c) if masked bits are known zero.
+def : Pat<(parallel (or_is_add GR8:$src1, imm:$src2),
+                    (implicit EFLAGS)),
+          (ADD8ri GR8:$src1, imm:$src2)>;
+def : Pat<(parallel (or_is_add GR16:$src1, imm:$src2),
+                    (implicit EFLAGS)),
+          (ADD16ri GR16:$src1, imm:$src2)>;
+def : Pat<(parallel (or_is_add GR32:$src1, imm:$src2),
+                    (implicit EFLAGS)),
+          (ADD32ri GR32:$src1, imm:$src2)>;
+def : Pat<(parallel (or_is_add GR16:$src1, i16immSExt8:$src2),
+                    (implicit EFLAGS)),
+          (ADD16ri8 GR16:$src1, i16immSExt8:$src2)>;
+def : Pat<(parallel (or_is_add GR32:$src1, i32immSExt8:$src2),
+                    (implicit EFLAGS)),
+          (ADD32ri8 GR32:$src1, i32immSExt8:$src2)>;
+
 //===----------------------------------------------------------------------===//
 // EFLAGS-defining Patterns
 //===----------------------------------------------------------------------===//
diff --git a/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll b/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll
index 8a0b244a23f..3cd54169745 100644
--- a/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll
+++ b/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll
@@ -1,12 +1,18 @@
-; RUN: llc < %s | grep -E {sar|shl|mov|or} | count 4
+; RUN: llc < %s | FileCheck %s
+
 ; Check that the shr(shl X, 56), 48) is not mistakenly turned into
 ; a shr (X, -8) that gets subsequently "optimized away" as undef
 ; PR4254
+
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define i64 @foo(i64 %b) nounwind readnone {
 entry:
+; CHECK: foo:
+; CHECK: shlq $56, %rdi
+; CHECK: sarq $48, %rdi
+; CHECK: leaq 1(%rdi), %rax
 	%shl = shl i64 %b, 56		; <i64> [#uses=1]
 	%shr = ashr i64 %shl, 48		; <i64> [#uses=1]
 	%add5 = or i64 %shr, 1		; <i64> [#uses=1]
diff --git a/test/CodeGen/X86/3addr-or.ll b/test/CodeGen/X86/3addr-or.ll
new file mode 100644
index 00000000000..395ba46aab3
--- /dev/null
+++ b/test/CodeGen/X86/3addr-or.ll
@@ -0,0 +1,11 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+; rdar://7527734
+
+define i32 @test(i32 %x) nounwind readnone ssp {
+entry:
+; CHECK: test:
+; CHECK: leal 3(%rdi), %eax
+  %0 = shl i32 %x, 5                              ; <i32> [#uses=1]
+  %1 = or i32 %0, 3                               ; <i32> [#uses=1]
+  ret i32 %1
+}