Merging r312905:

------------------------------------------------------------------------
r312905 | dylanmckay | 2017-09-11 22:32:51 +1200 (Mon, 11 Sep 2017) | 10 lines

[AVR] Enable the '__do_copy_data' function

Also enables '__do_clear_bss'.

These functions are automaticalled called by the CRT if they are
declared.

We need these to be called otherwise RAM will start completely
uninitialised, even though we need to copy RAM variables from progmem to
RAM.
------------------------------------------------------------------------

llvm-svn: 314356

4 files changed, 32 insertions, 0 deletions

diff --git a/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.cpp b/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.cpp
index a2d8c16eeb8c..2b45d9adc7e9 100644
--- a/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.cpp
+++ b/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.cpp
@@ -13,6 +13,8 @@
 
 #include "AVRTargetStreamer.h"
 
+#include "llvm/MC/MCContext.h"
+
 namespace llvm {
 
 AVRTargetStreamer::AVRTargetStreamer(MCStreamer &S) : MCTargetStreamer(S) {}
@@ -20,5 +22,23 @@ AVRTargetStreamer::AVRTargetStreamer(MCStreamer &S) : MCTargetStreamer(S) {}
 AVRTargetAsmStreamer::AVRTargetAsmStreamer(MCStreamer &S)
     : AVRTargetStreamer(S) {}
 
+void AVRTargetStreamer::finish() {
+  MCStreamer &OS = getStreamer();
+  MCContext &Context = OS.getContext();
+
+  MCSymbol *DoCopyData = Context.getOrCreateSymbol("__do_copy_data");
+  MCSymbol *DoClearBss = Context.getOrCreateSymbol("__do_clear_bss");
+
+  // FIXME: We can disable __do_copy_data if there are no static RAM variables.
+
+  OS.emitRawComment(" Declaring this symbol tells the CRT that it should");
+  OS.emitRawComment("copy all variables from program memory to RAM on startup");
+  OS.EmitSymbolAttribute(DoCopyData, MCSA_Global);
+
+  OS.emitRawComment(" Declaring this symbol tells the CRT that it should");
+  OS.emitRawComment("clear the zeroed data section on startup");
+  OS.EmitSymbolAttribute(DoClearBss, MCSA_Global);
+}
+
 } // end namespace llvm
 
diff --git a/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.h b/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.h
index 99a536699ae9..815088b0a5de 100644
--- a/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.h
+++ b/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.h
@@ -19,6 +19,8 @@ class MCStreamer;
 class AVRTargetStreamer : public MCTargetStreamer {
 public:
   explicit AVRTargetStreamer(MCStreamer &S);
+
+  void finish() override;
 };
 
 /// A target streamer for textual AVR assembly code.
diff --git a/llvm/test/CodeGen/AVR/clear-bss.ll b/llvm/test/CodeGen/AVR/clear-bss.ll
new file mode 100644
index 000000000000..9c63815c098d
--- /dev/null
+++ b/llvm/test/CodeGen/AVR/clear-bss.ll
@@ -0,0 +1,5 @@
+; RUN: llc < %s -march=avr | FileCheck %s
+
+; CHECK: .globl __do_clear_bss
+@zeroed = internal constant [3 x i8] zeroinitializer
+
diff --git a/llvm/test/CodeGen/AVR/copy-data-to-ram.ll b/llvm/test/CodeGen/AVR/copy-data-to-ram.ll
new file mode 100644
index 000000000000..021cc0f1a7f4
--- /dev/null
+++ b/llvm/test/CodeGen/AVR/copy-data-to-ram.ll
@@ -0,0 +1,5 @@
+; RUN: llc < %s -march=avr | FileCheck %s
+
+; CHECK: .globl __do_copy_data
+@str = internal global [3 x i8] c"foo"
+