From dab6e68a8396475af5acbf53397f93c6b52e2e71 Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Sat, 8 Oct 2022 15:34:46 -0600
Subject: Implement LDR/STR decode

---
 rtl/core/decode/ldst/misc.sv     | 28 ++++++++++++++++++++++++++++
 rtl/core/decode/ldst/multiple.sv | 32 ++++++++++++++++++++++++++++++++
 rtl/core/decode/ldst/single.sv   | 30 ++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100644 rtl/core/decode/ldst/misc.sv
 create mode 100644 rtl/core/decode/ldst/multiple.sv
 create mode 100644 rtl/core/decode/ldst/single.sv

(limited to 'rtl/core/decode/ldst')

diff --git a/rtl/core/decode/ldst/misc.sv b/rtl/core/decode/ldst/misc.sv
new file mode 100644
index 0000000..de2428f
--- /dev/null
+++ b/rtl/core/decode/ldst/misc.sv
@@ -0,0 +1,28 @@
+`include "core/isa.sv"
+`include "core/uarch.sv"
+
+module core_decode_ldst_misc
+(
+	input  word        insn,
+
+	output ldst_decode decode
+);
+
+	logic p, w;
+
+	assign decode.rn = insn `FIELD_LDST_MISC_RN;
+	assign decode.rd = insn `FIELD_LDST_MISC_RD;
+	assign decode.size = insn `FIELD_LDST_MISC_H ? LDST_HALF : LDST_BYTE;
+	assign decode.load = insn `FIELD_LDST_LD;
+	assign decode.increment = insn `FIELD_LDST_MISC_U;
+	assign decode.writeback = !p || w;
+	assign decode.sign_extend = insn `FIELD_LDST_MISC_S;
+	assign decode.pre_indexed = p && w;
+	assign decode.unprivileged = 0;
+	assign decode.user_regs = 0;
+	assign decode.reg_list = 16'b0;
+
+	assign p = insn `FIELD_LDST_MISC_P;
+	assign w = insn `FIELD_LDST_MISC_W;
+
+endmodule
diff --git a/rtl/core/decode/ldst/multiple.sv b/rtl/core/decode/ldst/multiple.sv
new file mode 100644
index 0000000..24e8e5b
--- /dev/null
+++ b/rtl/core/decode/ldst/multiple.sv
@@ -0,0 +1,32 @@
+`include "core/isa.sv"
+`include "core/uarch.sv"
+
+module core_decode_ldst_multiple
+(
+	input  word        insn,
+
+	output ldst_decode decode,
+	output logic       restore_spsr
+);
+
+	logic s, l;
+	logic[15:0] reg_list;
+
+	assign decode.rn = insn `FIELD_LDST_MULT_RN;
+	assign decode.size = LDST_WORD;
+	assign decode.load = l;
+	assign decode.increment = insn `FIELD_LDST_MULT_U;
+	assign decode.writeback = insn `FIELD_LDST_MULT_W;
+	assign decode.sign_extend = 0;
+	assign decode.pre_indexed = insn `FIELD_LDST_MULT_P;
+	assign decode.unprivileged = 0;
+	assign decode.user_regs = s && (!l || !reg_list[`R15]);
+	assign decode.reg_list = reg_list;
+
+	assign s = insn `FIELD_LDST_MULT_S;
+	assign l = insn `FIELD_LDST_LD;
+
+	assign reg_list = insn `FIELD_LDST_MULT_LIST;
+	assign restore_spsr = s && l && reg_list[`R15];
+
+endmodule
diff --git a/rtl/core/decode/ldst/single.sv b/rtl/core/decode/ldst/single.sv
new file mode 100644
index 0000000..5bcb638
--- /dev/null
+++ b/rtl/core/decode/ldst/single.sv
@@ -0,0 +1,30 @@
+`include "core/isa.sv"
+`include "core/uarch.sv"
+
+module core_decode_ldst_single
+(
+	input  word        insn,
+
+	output ldst_decode decode,
+	output logic       snd_is_imm
+);
+
+	logic p, w;
+
+	assign decode.rn = insn `FIELD_LDST_SINGLE_RN;
+	assign decode.rd = insn `FIELD_LDST_SINGLE_RD;
+	assign decode.size = insn `FIELD_LDST_SINGLE_B ? LDST_BYTE : LDST_WORD;
+	assign decode.load = insn `FIELD_LDST_LD;
+	assign decode.increment = insn `FIELD_LDST_SINGLE_U;
+	assign decode.writeback = !p || w;
+	assign decode.sign_extend = 0;
+	assign decode.pre_indexed = p && w;
+	assign decode.unprivileged = !p && w;
+	assign decode.user_regs = 0;
+	assign decode.reg_list = 16'b0;
+
+	assign p = insn `FIELD_LDST_SINGLE_P;
+	assign w = insn `FIELD_LDST_SINGLE_W;
+	assign snd_is_imm = !insn `FIELD_LDST_SINGLE_REG;
+
+endmodule
-- 
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