RISC-V: add comment RVSystemLinkageProperties::initialize()

Signed-off-by: Jan Vrany <jan.vrany@fit.cvut.cz>
eclipse · Apr 7, 2021 · d9c35bd · d9c35bd
1 parent 43983d7
commit d9c35bd
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/compiler/riscv/codegen/RVSystemLinkage.cpp b/compiler/riscv/codegen/RVSystemLinkage.cpp
@@ -58,6 +58,13 @@ TR::RVSystemLinkageProperties::RVSystemLinkageProperties()
    {
    _properties = IntegersInRegisters|FloatsInRegisters|RightToLeft;
 
+   /*
+    * _registerFlags for each register are defined in architectural order,
+    * that is, from x0 to x31, f0 to f31.
+    *
+    * See https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#integer-register-convention
+    */
+
    _registerFlags[TR::RealRegister::zero] = Preserved|RV_Reserved; // zero
    _registerFlags[TR::RealRegister::ra]   = Preserved|RV_Reserved; // return address
    _registerFlags[TR::RealRegister::sp]   = Preserved|RV_Reserved; // sp