[MSP430] Fix data layout string.

[pftbest]

Summary

Without this patch some types have incorrect size and/or alignment
according to the MSP430 EABI.

[asl]

LGTM. Thanks for working on this!

lib/Target/MSP430/MSP430TargetMachine.cpp

 }
 
 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
   if (!RM.hasValue())
     return Reloc::Static;
   return *RM;
 }
 
+static std::string computeDataLayout(const Triple &TT, StringRef CPU,
+                                     const TargetOptions &Options) {
+  return "e-m:e-p:16:16-i32:16-i64:16-f32:16-f64:16-a:8-n8:16-S16";
+}
+
 MSP430TargetMachine::MSP430TargetMachine(const Target &T, const Triple &TT,
                                          StringRef CPU, StringRef FS,
                                          const TargetOptions &Options,
                                          Optional<Reloc::Model> RM,
                                          CodeModel::Model CM,
                                          CodeGenOpt::Level OL)
-    : LLVMTargetMachine(T, "e-m:e-p:16:16-i32:16:32-a:16-n8:16", TT, CPU, FS,
+    : LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options), TT, CPU, FS,
                         Options, getEffectiveRelocModel(RM), CM, OL),
       TLOF(make_unique<TargetLoweringObjectFileELF>()),
-      // FIXME: Check DataLayout string.
       Subtarget(TT, CPU, FS, *this) {
   initAsmInfo();
 }
 
 MSP430TargetMachine::~MSP430TargetMachine() {}
 
 namespace {
 /// MSP430 Code Generator Pass Configuration Options.

test/CodeGen/MSP430/Inst16mm.ll

  %y = alloca i32, align 2                        ; <i32*> [#uses=1]
  store i16 0, i16* %retval
  %tmp = load i32, i32* %y                             ; <i32> [#uses=1]
  store i32 %tmp, i32* %x
  store i16 0, i16* %retval
  %0 = load i16, i16* %retval                          ; <i16> [#uses=1]
  ret i16 %0
 ; CHECK-LABEL: mov2:
-; CHECK:  mov.w 2(r1), 6(r1)
 ; CHECK:  mov.w 0(r1), 4(r1)
+; CHECK:  mov.w 2(r1), 6(r1)
 }

test/CodeGen/MSP430/struct_layout.ll

+; RUN: llc < %s | FileCheck %s
+
+target triple = "msp430"
+
+%struct.X = type { i8 }
+
+; CHECK-LABEL: @foo
+; CHECK: sub.w   #4, r1
+; CHECK: mov.b   #1, 3(r1)
+define void @foo() {
+  %1 = alloca %struct.X
+  %2 = alloca %struct.X
+  %3 = alloca %struct.X
+  %4 = getelementptr inbounds %struct.X, %struct.X* %1, i32 0, i32 0
+  store i8 1, i8* %4
+  %5 = getelementptr inbounds %struct.X, %struct.X* %2, i32 0, i32 0
+  store i8 1, i8* %5
+  %6 = getelementptr inbounds %struct.X, %struct.X* %3, i32 0, i32 0
+  store i8 1, i8* %6
+  ret void
+}
+
+; CHECK-LABEL: @bar
+; CHECK: sub.w   #4, r1
+; CHECK: mov.b   #1, 3(r1)
+define void @bar() {
+  %1 = alloca [3 x %struct.X]
+  %2 = getelementptr inbounds [3 x %struct.X], [3 x %struct.X]* %1, i16 0, i16 0
+  %3 = getelementptr inbounds %struct.X, %struct.X* %2, i32 0, i32 0
+  store i8 1, i8* %3
+  %4 = getelementptr inbounds [3 x %struct.X], [3 x %struct.X]* %1, i16 0, i16 1
+  %5 = getelementptr inbounds %struct.X, %struct.X* %4, i32 0, i32 0
+  store i8 1, i8* %5
+  %6 = getelementptr inbounds [3 x %struct.X], [3 x %struct.X]* %1, i16 0, i16 2
+  %7 = getelementptr inbounds %struct.X, %struct.X* %6, i32 0, i32 0
+  store i8 1, i8* %7
+  ret void
+}
+
+%struct.Y = type { i8, i16 }
+
+; CHECK-LABEL: @baz
+; CHECK: sub.w   #8, r1
+; CHECK: mov.w   #2, 6(r1)
+define void @baz() {
+  %1 = alloca %struct.Y, align 2
+  %2 = alloca %struct.Y, align 2
+  %3 = getelementptr inbounds %struct.Y, %struct.Y* %1, i32 0, i32 0
+  store i8 1, i8* %3, align 2
+  %4 = getelementptr inbounds %struct.Y, %struct.Y* %1, i32 0, i32 1
+  store i16 2, i16* %4, align 2
+  %5 = getelementptr inbounds %struct.Y, %struct.Y* %2, i32 0, i32 0
+  store i8 1, i8* %5, align 2
+  %6 = getelementptr inbounds %struct.Y, %struct.Y* %2, i32 0, i32 1
+  store i16 2, i16* %6, align 2
+  ret void
+}