Enable ETW_EBP_FRAMED flag on System V systems.

Enable the ETW_EBP_FRAMED flag on System V systems to allow for using
frame pointer (RBP) for mostly all functions.
The change includes:
1. Removing RBP from all the lists of registers that the RA uses to assign
to tmps/vars/etc.
2. Enable generation of unwind info for pushing of REG_FPBASE even if not included in callee-save list
of registers.
3 Fixed a conservative assert - for System V systems stack offset for reg
passed argument can be 0 or even positive.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/jit/unwindamd64.cpp b/src/jit/unwindamd64.cpp
index cf83ed3015..644d8749d7 100644
--- a/src/jit/unwindamd64.cpp
+++ b/src/jit/unwindamd64.cpp
@@ -121,7 +121,15 @@ void Compiler::unwindPush(regNumber reg)
     unsigned int cbProlog = unwindGetCurrentOffset(func);
     noway_assert((BYTE)cbProlog == cbProlog);
     code->CodeOffset = (BYTE)cbProlog;
-    if (RBM_CALLEE_SAVED & genRegMask(reg))
+    if ((RBM_CALLEE_SAVED & genRegMask(reg))
+#if ETW_EBP_FRAMED
+        // In case of ETW_EBP_FRAMED defined the REG_FPBASE (RBP)
+        // is excluded from the callee-save register list.
+        // Make sure the register gets PUSH unwind info in this case,
+        // since it is pushed as a frame register.
+        || (reg == REG_FPBASE)
+#endif // ETW_EBP_FRAMED
+        )
     {
         code->UnwindOp = UWOP_PUSH_NONVOL;
         code->OpInfo = (BYTE)reg;