RISC-V: Fix epilogue unwind info with fp and single sp adjust.

	gcc/
	* config/riscv/riscv.c (epilogue_cfa_sp_offset): New.
	(riscv_restore_reg): If restoring HARD_FRAME_POINTER_REGNUM, and
	epilogue_cfa_sp_offset set, then add REG_CFA_DEF_CFA regnote.
	(riscv_expand_epilogue): Initialize epilogue_cfa_sp_offset.  Set it
	to step2 if frame_pointer_needed and step1 is 0.

From-SVN: r266241

gcc/ChangeLog

+2018-11-17  Jim Wilson  <jimw@sifive.com>
+
+	* config/riscv/riscv.c (epilogue_cfa_sp_offset): New.
+	(riscv_restore_reg): If restoring HARD_FRAME_POINTER_REGNUM, and
+	epilogue_cfa_sp_offset set, then add REG_CFA_DEF_CFA regnote.
+	(riscv_expand_epilogue): Initialize epilogue_cfa_sp_offset.  Set it
+	to step2 if frame_pointer_needed and step1 is 0.
+
 2018-11-17  Sandra Loosemore  <sandra@codesourcery.com>
 
 	PR c++/4225

gcc/config/riscv/riscv.c

@@ -237,6 +237,11 @@ bool riscv_slow_unaligned_access_p;
 /* Stack alignment to assume/maintain.  */
 unsigned riscv_stack_boundary;
 
+/* If non-zero, this is an offset to be added to SP to redefine the CFA
+   when restoring the FP register from the stack.  Only valid when generating
+   the epilogue.  */
+static int epilogue_cfa_sp_offset;
+
 /* Which tuning parameters to use.  */
 static const struct riscv_tune_info *tune_info;
 
@@ -3627,8 +3632,15 @@ riscv_restore_reg (rtx reg, rtx mem)
   rtx insn = riscv_emit_move (reg, mem);
   rtx dwarf = NULL_RTX;
   dwarf = alloc_reg_note (REG_CFA_RESTORE, reg, dwarf);
-  REG_NOTES (insn) = dwarf;
 
+  if (epilogue_cfa_sp_offset && REGNO (reg) == HARD_FRAME_POINTER_REGNUM)
+    {
+      rtx cfa_adjust_rtx = gen_rtx_PLUS (Pmode, stack_pointer_rtx,
+					 GEN_INT (epilogue_cfa_sp_offset));
+      dwarf = alloc_reg_note (REG_CFA_DEF_CFA, cfa_adjust_rtx, dwarf);
+    }
+
+  REG_NOTES (insn) = dwarf;
   RTX_FRAME_RELATED_P (insn) = 1;
 }
 
@@ -3877,6 +3889,9 @@ riscv_expand_epilogue (int style)
       return;
     }
 
+  /* Reset the epilogue cfa info before starting to emit the epilogue.  */
+  epilogue_cfa_sp_offset = 0;
+
   /* Move past any dynamic stack allocations.  */
   if (cfun->calls_alloca)
     {
@@ -3941,6 +3956,12 @@ riscv_expand_epilogue (int style)
 
       REG_NOTES (insn) = dwarf;
     }
+  else if (frame_pointer_needed)
+    {
+      /* Tell riscv_restore_reg to emit dwarf to redefine CFA when restoring
+	 old value of FP.  */
+      epilogue_cfa_sp_offset = step2;
+    }
 
   if (use_restore_libcall)
     frame->mask = 0; /* Temporarily fib that we need not save GPRs.  */