Restructure the codegen to make architectural depedency explicit.
The original Codegen.c is broken into three components:
- CodegenCommon.c (arch-independend)
- CodegenFactory.c (Thumb1/2 dependent)
- CodegenDriver.c (Dalvik dependent)
For the Thumb/Thumb2 directories, each contain the followin three files:
- Factory.c (low-level routines for instruction selections)
- Gen.c (invoke the ISA-specific instruction selection routines)
- Ralloc.c (arch-dependent register pools)
The FP directory contains FP-specific codegen routines depending on
Thumb/Thumb2/VFP/PortableFP:
- Thumb2VFP.c
- ThumbVFP.c
- ThumbPortableFP.c
Then the hierarchy is formed by stacking these files in the following top-down
order:
1 CodegenCommon.c
2 Thumb[2]/Factory.c
3 CodegenFactory.c
4 Thumb[2]/Gen.c
5 FP stuff
6 Thumb[2]/Ralloc.c
7 CodegenDriver.c
diff --git a/vm/compiler/codegen/arm/README.txt b/vm/compiler/codegen/arm/README.txt
new file mode 100644
index 0000000..6698ac3
--- /dev/null
+++ b/vm/compiler/codegen/arm/README.txt
@@ -0,0 +1,49 @@
+The codegen file for the ARM-based JIT is composed by files broken by
+functionality hierarchies. The goal is to separate architectural dependent
+and independent components to facilitate maintenance and future extension.
+
+For example, the codegen file for armv7-a is assembled by the following
+components:
+
+--
+
+/* Architectural independent building blocks */
+#include "../CodegenCommon.c"
+
+/* Thumb2-specific factory utilities */
+#include "../Thumb2/Factory.c"
+/* Factory utilities dependent on arch-specific features */
+#include "../CodegenFactory.c"
+
+/* Thumb2-specific codegen routines */
+#include "../Thumb2/Gen.c"
+/* Thumb2+VFP codegen routines */
+#include "../FP/Thumb2VFP.c"
+
+/* Thumb2-specific register allocation */
+#include "../Thumb2/Ralloc.c"
+
+/* MIR2LIR dispatcher and architectural independent codegen routines */
+#include "../CodegenDriver.c"
+
+/* Architecture manifest */
+#include "ArchVariant.c"
+
+--
+
+For the Thumb/Thumb2 directories, each contain the followin three files:
+
+- Factory.c (low-level routines for instruction selections)
+- Gen.c (invoke the ISA-specific instruction selection routines)
+- Ralloc.c (arch-dependent register pools)
+
+The FP directory contains FP-specific codegen routines depending on
+Thumb/Thumb2/VFP/PortableFP:
+
+- Thumb2VFP.c
+- ThumbVFP.c
+- ThumbPortableFP.c
+
+In this way the dependency between generic and specific code tied to
+particular architectures can be explicitly represented.
+