[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: 312905

diff --git a/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.cpp b/llvm/lib/Target/AVR/MCTargetDesc/AVRTargetStreamer.cpp
index a2d8c16..2b45d9a 100644 (file)
--- 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 99a5366..815088b 100644 (file)
--- 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 (file)
index 0000000..9c63815
--- /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 (file)
index 0000000..021cc0f
--- /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"
+