X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/e5fb7d8642fb3b0956fdb110018289a866b376c8..4caf81e0cb02f814642cd7dc1a1d5ac05415415e:/Decode.v

diff --git a/Decode.v b/Decode.v
index 85aa439..22c6eae 100644
--- a/Decode.v
+++ b/Decode.v
@@ -26,6 +26,7 @@ module Decode(
 	wire [31:0] shift_oper;
 	wire [31:0] shift_res;
 	wire shift_cflag_out;
+	wire [31:0] rotate_res;
 
 	assign regs0 = (read_0 == 4'b1111) ? rpc : rdata_0;
 	assign regs1 = (read_1 == 4'b1111) ? rpc : rdata_1;
@@ -38,6 +39,10 @@ module Decode(
 	                           .res(shift_res),
 	                           .cflag_out(shift_cflag_out));
 
+	SuckLessRotator whirr(.oper({24'b0, insn[7:0]}),
+	                      .amt(insn[11:8]),
+	                      .res(rotate_res));
+
 	always @(*)
 		casez (insn)
 		32'b????000000??????????????1001????,	/* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
@@ -152,7 +157,7 @@ module Decode(
         	end
                 32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits only) */
                 	if(insn[25]) begin     /* the constant case */
-				op0_out = ({24'b0, insn[7:0]} >> {insn[11:8], 1'b0}) | ({24'b0, insn[7:0]} << (5'b0 - {insn[11:8], 1'b0}));
+				op0_out = rotate_res;
 			end else begin
 				op0_out = regs0;
 			end
@@ -161,7 +166,7 @@ module Decode(
 			op0_out = regs0;
 			if(insn[25]) begin     /* the constant case */
 				carry_out = incpsr[`CPSR_C];
-				op1_out = ({24'b0, insn[7:0]} >> {insn[11:8], 1'b0}) | ({24'b0, insn[7:0]} << (5'b0 - {insn[11:8], 1'b0}));
+				op1_out = rotate_res;
 			end else begin
 				carry_out = shift_cflag_out;
 				op1_out = shift_res;
@@ -310,10 +315,24 @@ module SuckLessShifter(
 
 	/* do a barrel shift */
 	assign stage1 = amt[5] ? {is_rot ? oper : {32{pushbits}}, oper[31]} : {oper, carryin};
-	assign stage2 = amt[4] ? {is_rot ? stage1[15:0] : {16{pushbits}}, stage1[31:16], stage1[16]} : stage1;
-	assign stage3 = amt[3] ? {is_rot ? stage2[7:0] : {8{pushbits}}, stage2[31:8], stage2[8]} : stage2;
-	assign stage4 = amt[2] ? {is_rot ? stage3[3:0] : {4{pushbits}}, stage3[31:4], stage3[4]} : stage3;
-	assign stage5 = amt[1] ? {is_rot ? stage4[1:0] : {2{pushbits}}, stage4[31:2], stage4[2]} : stage4;
-	assign {res, carryout} = amt[0] ? {is_rot ? stage4[0] : pushbits, stage5[31:1], stage5[1]} : stage5;
+	assign stage2 = amt[4] ? {is_rot ? stage1[16:1] : {16{pushbits}}, stage1[32:17], stage1[16]} : stage1;
+	assign stage3 = amt[3] ? {is_rot ? stage2[8:1] : {8{pushbits}}, stage2[32:9], stage2[8]} : stage2;
+	assign stage4 = amt[2] ? {is_rot ? stage3[4:1] : {4{pushbits}}, stage3[32:5], stage3[4]} : stage3;
+	assign stage5 = amt[1] ? {is_rot ? stage4[2:1] : {2{pushbits}}, stage4[32:3], stage4[2]} : stage4;
+	assign {res, carryout} = amt[0] ? {is_rot ? stage5[1] : pushbits, stage5[32:2], stage5[1]} : stage5;
+
+endmodule
+
+module SuckLessRotator(
+	input [31:0] oper,
+	input [3:0] amt,
+	output [31:0] res
+);
+
+	wire [31:0] stage1, stage2, stage3;
+	assign stage1 = amt[3] ? {oper[15:0], oper[31:16]} : oper;
+	assign stage2 = amt[2] ? {stage1[7:0], stage1[31:8]} : stage1;
+	assign stage3 = amt[1] ? {stage2[3:0], stage2[31:4]} : stage2;
+	assign res    = amt[0] ? {stage3[1:0], stage3[31:2]} : stage3;
 
 endmodule