+/* Fallback alpha frame unwinder. Uses instruction scanning and knows
+ something about the traditional layout of alpha stack frames. */
+
+struct alpha_heuristic_unwind_cache
+{
+ CORE_ADDR vfp;
+ CORE_ADDR start_pc;
+ trad_frame_saved_reg *saved_regs;
+ int return_reg;
+};
+
+/* If a probing loop sequence starts at PC, simulate it and compute
+ FRAME_SIZE and PC after its execution. Otherwise, return with PC and
+ FRAME_SIZE unchanged. */
+
+static void
+alpha_heuristic_analyze_probing_loop (struct gdbarch *gdbarch, CORE_ADDR *pc,
+ int *frame_size)
+{
+ CORE_ADDR cur_pc = *pc;
+ int cur_frame_size = *frame_size;
+ int nb_of_iterations, reg_index, reg_probe;
+ unsigned int insn;
+
+ /* The following pattern is recognized as a probing loop:
+
+ lda REG_INDEX,NB_OF_ITERATIONS
+ lda REG_PROBE,<immediate>(sp)
+
+ LOOP_START:
+ stq zero,<immediate>(REG_PROBE)
+ subq REG_INDEX,0x1,REG_INDEX
+ lda REG_PROBE,<immediate>(REG_PROBE)
+ bne REG_INDEX, LOOP_START
+
+ lda sp,<immediate>(REG_PROBE)
+
+ If anything different is found, the function returns without
+ changing PC and FRAME_SIZE. Otherwise, PC will point immediately
+ after this sequence, and FRAME_SIZE will be updated. */
+
+ /* lda REG_INDEX,NB_OF_ITERATIONS */
+
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != lda_opcode)
+ return;
+ reg_index = MEM_RA (insn);
+ nb_of_iterations = MEM_DISP (insn);
+
+ /* lda REG_PROBE,<immediate>(sp) */
+
+ cur_pc += ALPHA_INSN_SIZE;
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != lda_opcode
+ || MEM_RB (insn) != ALPHA_SP_REGNUM)
+ return;
+ reg_probe = MEM_RA (insn);
+ cur_frame_size -= MEM_DISP (insn);
+
+ /* stq zero,<immediate>(REG_PROBE) */
+
+ cur_pc += ALPHA_INSN_SIZE;
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != stq_opcode
+ || MEM_RA (insn) != 0x1f
+ || MEM_RB (insn) != reg_probe)
+ return;
+
+ /* subq REG_INDEX,0x1,REG_INDEX */
+
+ cur_pc += ALPHA_INSN_SIZE;
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != subq_opcode
+ || !OPR_HAS_IMMEDIATE (insn)
+ || OPR_FUNCTION (insn) != subq_function
+ || OPR_LIT(insn) != 1
+ || OPR_RA (insn) != reg_index
+ || OPR_RC (insn) != reg_index)
+ return;
+
+ /* lda REG_PROBE,<immediate>(REG_PROBE) */
+
+ cur_pc += ALPHA_INSN_SIZE;
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != lda_opcode
+ || MEM_RA (insn) != reg_probe
+ || MEM_RB (insn) != reg_probe)
+ return;
+ cur_frame_size -= MEM_DISP (insn) * nb_of_iterations;
+
+ /* bne REG_INDEX, LOOP_START */
+
+ cur_pc += ALPHA_INSN_SIZE;
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != bne_opcode
+ || MEM_RA (insn) != reg_index)
+ return;
+
+ /* lda sp,<immediate>(REG_PROBE) */
+
+ cur_pc += ALPHA_INSN_SIZE;
+ insn = alpha_read_insn (gdbarch, cur_pc);
+ if (INSN_OPCODE (insn) != lda_opcode
+ || MEM_RA (insn) != ALPHA_SP_REGNUM
+ || MEM_RB (insn) != reg_probe)
+ return;
+ cur_frame_size -= MEM_DISP (insn);
+
+ *pc = cur_pc;
+ *frame_size = cur_frame_size;
+}
+