diff --git a/test/Instrumentation/AddressSanitizer/freebsd.ll b/test/Instrumentation/AddressSanitizer/freebsd.ll
index 5178432d63a..f940b52b41f 100644
--- a/test/Instrumentation/AddressSanitizer/freebsd.ll
+++ b/test/Instrumentation/AddressSanitizer/freebsd.ll
@@ -1,11 +1,11 @@
 ; RUN: opt < %s -asan -asan-module -S \
 ; RUN:     -mtriple=i386-unknown-freebsd \
-; RUN:     -default-data-layout="e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" | \
+; RUN:     -data-layout="e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" | \
 ; RUN:     FileCheck --check-prefix=CHECK-32 %s
 
 ; RUN: opt < %s -asan -asan-module -S \
 ; RUN:     -mtriple=x86_64-unknown-freebsd \
-; RUN:     -default-data-layout="e-m:e-i64:64-f80:128-n8:16:32:64-S128" | \
+; RUN:     -data-layout="e-m:e-i64:64-f80:128-n8:16:32:64-S128" | \
 ; RUN:     FileCheck --check-prefix=CHECK-64 %s
 
 define i32 @read_4_bytes(i32* %a) sanitize_address {
diff --git a/test/Other/constant-fold-gep.ll b/test/Other/constant-fold-gep.ll
index 77c43a200c0..8028b4fff98 100644
--- a/test/Other/constant-fold-gep.ll
+++ b/test/Other/constant-fold-gep.ll
@@ -8,7 +8,7 @@
 
 ; "TO" - Optimizations and targetdata. This tests target-dependent
 ; folding in the optimizers.
-; RUN: opt -S -o - -instcombine -globalopt -default-data-layout="e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" < %s | FileCheck --check-prefix=TO %s
+; RUN: opt -S -o - -instcombine -globalopt -data-layout="e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" < %s | FileCheck --check-prefix=TO %s
 
 ; "SCEV" - ScalarEvolution with default target layout
 ; RUN: opt -analyze -scalar-evolution < %s | FileCheck --check-prefix=SCEV %s
diff --git a/test/Transforms/ConstProp/loads.ll b/test/Transforms/ConstProp/loads.ll
index 89387ad06ba..dce2068a8d5 100644
--- a/test/Transforms/ConstProp/loads.ll
+++ b/test/Transforms/ConstProp/loads.ll
@@ -1,5 +1,5 @@
-; RUN: opt < %s -default-data-layout="e-p:64:64:64-p1:16:16:16-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-s0:64:64" -instcombine -S | FileCheck %s --check-prefix=LE
-; RUN: opt < %s -default-data-layout="E-p:64:64:64-p1:16:16:16-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-s0:64:64" -instcombine -S | FileCheck %s --check-prefix=BE
+; RUN: opt < %s -data-layout="e-p:64:64:64-p1:16:16:16-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-s0:64:64" -instcombine -S | FileCheck %s --check-prefix=LE
+; RUN: opt < %s -data-layout="E-p:64:64:64-p1:16:16:16-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-s0:64:64" -instcombine -S | FileCheck %s --check-prefix=BE
 
 ; {{ 0xDEADBEEF, 0xBA }, 0xCAFEBABE}
 @g1 = constant {{i32,i8},i32} {{i32,i8} { i32 -559038737, i8 186 }, i32 -889275714 }
diff --git a/test/Transforms/GVN/PRE/rle-addrspace-cast.ll b/test/Transforms/GVN/PRE/rle-addrspace-cast.ll
index 07fd7c11d1b..d8de5b360ba 100644
--- a/test/Transforms/GVN/PRE/rle-addrspace-cast.ll
+++ b/test/Transforms/GVN/PRE/rle-addrspace-cast.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -default-data-layout="e-p:32:32:32-p1:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-n8:16:32" -basicaa -gvn -S -die | FileCheck %s
+; RUN: opt < %s -data-layout="e-p:32:32:32-p1:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-n8:16:32" -basicaa -gvn -S -die | FileCheck %s
 
 define i8 @coerce_offset0_addrspacecast(i32 %V, i32* %P) {
   store i32 %V, i32* %P
diff --git a/test/Transforms/GVN/PRE/rle.ll b/test/Transforms/GVN/PRE/rle.ll
index c1946faab20..1d2cba2f1f6 100644
--- a/test/Transforms/GVN/PRE/rle.ll
+++ b/test/Transforms/GVN/PRE/rle.ll
@@ -1,5 +1,5 @@
-; RUN: opt < %s -default-data-layout="e-p:32:32:32-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-n8:16:32" -basicaa -gvn -S -die | FileCheck %s
-; RUN: opt < %s -default-data-layout="E-p:32:32:32-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-n32"      -basicaa -gvn -S -die | FileCheck %s
+; RUN: opt < %s -data-layout="e-p:32:32:32-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-n8:16:32" -basicaa -gvn -S -die | FileCheck %s
+; RUN: opt < %s -data-layout="E-p:32:32:32-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-n32"      -basicaa -gvn -S -die | FileCheck %s
 
 ;; Trivial RLE test.
 define i32 @test0(i32 %V, i32* %P) {
diff --git a/test/Transforms/IndVarSimplify/2011-11-01-lftrptr.ll b/test/Transforms/IndVarSimplify/2011-11-01-lftrptr.ll
index 402ae8cc05d..b9d571d9b64 100644
--- a/test/Transforms/IndVarSimplify/2011-11-01-lftrptr.ll
+++ b/test/Transforms/IndVarSimplify/2011-11-01-lftrptr.ll
@@ -1,5 +1,5 @@
-; RUN: opt < %s -indvars -S "-default-data-layout=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-s0:64:64-f80:128:128-n8:16:32:64" | FileCheck %s
-; RUN: opt < %s -indvars -S "-default-data-layout=e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32" | FileCheck %s
+; RUN: opt < %s -indvars -S "-data-layout=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-s0:64:64-f80:128:128-n8:16:32:64" | FileCheck %s
+; RUN: opt < %s -indvars -S "-data-layout=e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32" | FileCheck %s
 ;
 ; PR11279: Assertion !IVLimit->getType()->isPointerTy()
 ;
diff --git a/test/Transforms/InstCombine/2012-07-25-LoadPart.ll b/test/Transforms/InstCombine/2012-07-25-LoadPart.ll
index 14fcf52fe9a..71255ebbf81 100644
--- a/test/Transforms/InstCombine/2012-07-25-LoadPart.ll
+++ b/test/Transforms/InstCombine/2012-07-25-LoadPart.ll
@@ -1,5 +1,5 @@
-; RUN: opt < %s -default-data-layout="e-p:32:32:32" -instcombine -S | FileCheck %s --check-prefix=LE
-; RUN: opt < %s -default-data-layout="E-p:32:32:32" -instcombine -S | FileCheck %s --check-prefix=BE
+; RUN: opt < %s -data-layout="e-p:32:32:32" -instcombine -S | FileCheck %s --check-prefix=LE
+; RUN: opt < %s -data-layout="E-p:32:32:32" -instcombine -S | FileCheck %s --check-prefix=BE
 ; PR13442
 
 @test = constant [4 x i32] [i32 1, i32 2, i32 3, i32 4]
diff --git a/test/Transforms/InstCombine/alloca.ll b/test/Transforms/InstCombine/alloca.ll
index 2ee0372e5e0..f81f700e6cf 100644
--- a/test/Transforms/InstCombine/alloca.ll
+++ b/test/Transforms/InstCombine/alloca.ll
@@ -1,5 +1,5 @@
-; RUN: opt < %s -instcombine -S -default-data-layout="E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=CHECK -check-prefix=ALL
-; RUN: opt < %s -instcombine -S -default-data-layout="E-p:32:32:32-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=P32 -check-prefix=ALL
+; RUN: opt < %s -instcombine -S -data-layout="E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=CHECK -check-prefix=ALL
+; RUN: opt < %s -instcombine -S -data-layout="E-p:32:32:32-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=P32 -check-prefix=ALL
 ; RUN: opt < %s -instcombine -S | FileCheck %s -check-prefix=NODL -check-prefix=ALL
 
 
diff --git a/test/Transforms/InstCombine/load-cmp.ll b/test/Transforms/InstCombine/load-cmp.ll
index 75952e01c19..5746b7aa28d 100644
--- a/test/Transforms/InstCombine/load-cmp.ll
+++ b/test/Transforms/InstCombine/load-cmp.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -instcombine -S -default-data-layout="p:32:32:32-p1:16:16:16-n8:16:32:64" < %s | FileCheck %s
+; RUN: opt -instcombine -S -data-layout="p:32:32:32-p1:16:16:16-n8:16:32:64" < %s | FileCheck %s
 
 @G16 = internal constant [10 x i16] [i16 35, i16 82, i16 69, i16 81, i16 85,
                                      i16 73, i16 82, i16 69, i16 68, i16 0]
diff --git a/test/Transforms/InstCombine/narrow-switch.ll b/test/Transforms/InstCombine/narrow-switch.ll
index ccc17f87560..474bd820c8f 100644
--- a/test/Transforms/InstCombine/narrow-switch.ll
+++ b/test/Transforms/InstCombine/narrow-switch.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; Vary legal integer types in data layout.
-; RUN: opt < %s -instcombine -S -default-data-layout=n32    | FileCheck %s --check-prefix=ALL --check-prefix=CHECK32
-; RUN: opt < %s -instcombine -S -default-data-layout=n32:64 | FileCheck %s --check-prefix=ALL --check-prefix=CHECK64
+; RUN: opt < %s -instcombine -S -data-layout=n32    | FileCheck %s --check-prefix=ALL --check-prefix=CHECK32
+; RUN: opt < %s -instcombine -S -data-layout=n32:64 | FileCheck %s --check-prefix=ALL --check-prefix=CHECK64
 
 ; In all cases, the data-layout is irrelevant. We should shrink as much as possible in InstCombine
 ; and allow the backend to expand as much as needed to ensure optimal codegen for any target.
diff --git a/test/Transforms/SCCP/loadtest.ll b/test/Transforms/SCCP/loadtest.ll
index b88b44b7604..89c7371625a 100644
--- a/test/Transforms/SCCP/loadtest.ll
+++ b/test/Transforms/SCCP/loadtest.ll
@@ -1,7 +1,7 @@
 ; This test makes sure that these instructions are properly constant propagated.
 
-; RUN: opt < %s -default-data-layout="e-p:32:32" -sccp -S | FileCheck %s
-; RUN: opt < %s -default-data-layout="E-p:32:32" -sccp -S | FileCheck %s
+; RUN: opt < %s -data-layout="e-p:32:32" -sccp -S | FileCheck %s
+; RUN: opt < %s -data-layout="E-p:32:32" -sccp -S | FileCheck %s
 
 ; CHECK-NOT: load
 
diff --git a/test/Transforms/SimplifyCFG/switch_create.ll b/test/Transforms/SimplifyCFG/switch_create.ll
index 29d3a34a05e..c752636ae83 100644
--- a/test/Transforms/SimplifyCFG/switch_create.ll
+++ b/test/Transforms/SimplifyCFG/switch_create.ll
@@ -1,5 +1,5 @@
 ; RUN: opt -S -simplifycfg < %s | FileCheck %s
-; RUN: opt -S -default-data-layout="p:32:32-p1:16:16" -simplifycfg < %s | FileCheck -check-prefix=CHECK -check-prefix=DL %s
+; RUN: opt -S -data-layout="p:32:32-p1:16:16" -simplifycfg < %s | FileCheck -check-prefix=CHECK -check-prefix=DL %s
 
 declare void @foo1()
 
diff --git a/tools/opt/opt.cpp b/tools/opt/opt.cpp
index d5c74eef700..e61bc915bf8 100644
--- a/tools/opt/opt.cpp
+++ b/tools/opt/opt.cpp
@@ -201,10 +201,10 @@ static cl::opt<bool>
 PrintBreakpoints("print-breakpoints-for-testing",
                  cl::desc("Print select breakpoints location for testing"));
 
-static cl::opt<std::string>
-DefaultDataLayout("default-data-layout",
-          cl::desc("data layout string to use if not specified by module"),
-          cl::value_desc("layout-string"), cl::init(""));
+static cl::opt<std::string> ClDataLayout("data-layout",
+                                         cl::desc("data layout string to use"),
+                                         cl::value_desc("layout-string"),
+                                         cl::init(""));
 
 static cl::opt<bool> PreserveBitcodeUseListOrder(
     "preserve-bc-uselistorder",
@@ -448,9 +448,11 @@ int main(int argc, char **argv) {
     return 1;
   }
 
-  // If we are supposed to override the target triple, do so now.
+  // If we are supposed to override the target triple or data layout, do so now.
   if (!TargetTriple.empty())
     M->setTargetTriple(Triple::normalize(TargetTriple));
+  if (!ClDataLayout.empty())
+    M->setDataLayout(ClDataLayout);
 
   // Figure out what stream we are supposed to write to...
   std::unique_ptr<tool_output_file> Out;
@@ -530,12 +532,6 @@ int main(int argc, char **argv) {
     TLII.disableAllFunctions();
   Passes.add(new TargetLibraryInfoWrapperPass(TLII));
 
-  // Add an appropriate DataLayout instance for this module.
-  const DataLayout &DL = M->getDataLayout();
-  if (DL.isDefault() && !DefaultDataLayout.empty()) {
-    M->setDataLayout(DefaultDataLayout);
-  }
-
   // Add internal analysis passes from the target machine.
   Passes.add(createTargetTransformInfoWrapperPass(TM ? TM->getTargetIRAnalysis()
                                                      : TargetIRAnalysis()));