From 47fd042b9f8a92df1e1d59042068e7846c4ce808 Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddie@fpgeh.com>
Date: Fri, 19 Jul 2019 20:20:33 -0700
Subject: [PATCH] Indirection via $__soft_mul

---
 techlibs/common/mul2dsp.v     | 18 +++++++++---------
 techlibs/ice40/synth_ice40.cc |  1 +
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/techlibs/common/mul2dsp.v b/techlibs/common/mul2dsp.v
index 70c2c42c6..8b1ddefbf 100644
--- a/techlibs/common/mul2dsp.v
+++ b/techlibs/common/mul2dsp.v
@@ -28,9 +28,7 @@ module \$mul (A, B, Y);
 	output [Y_WIDTH-1:0] Y;
 
 	generate
-	if (A_SIGNED != B_SIGNED)
-		wire _TECHMAP_FAIL_ = 1;
-	else if (A_WIDTH <= `DSP_A_MAXWIDTH && B_WIDTH <= `DSP_B_MAXWIDTH)
+	if (A_SIGNED != B_SIGNED || A_WIDTH <= 1 || B_WIDTH <= 1)
 		wire _TECHMAP_FAIL_ = 1;
 	// NB: A_SIGNED == B_SIGNED == 0 from here
 	else if (A_WIDTH >= B_WIDTH)
@@ -212,7 +210,7 @@ module \$__mul (A, B, Y);
 endmodule
 
 (* techmap_celltype = "$__mul" *)
-module _90_internal_mul_to_external (A, B, Y); 
+module $__soft_mul (A, B, Y); 
 	parameter A_SIGNED = 0;
 	parameter B_SIGNED = 0;
 	parameter A_WIDTH = 1;
@@ -223,9 +221,11 @@ module _90_internal_mul_to_external (A, B, Y);
 	input [B_WIDTH-1:0] B;
 	output [Y_WIDTH-1:0] Y;
 
+	// Indirection necessary since mapping
+	//   back to $mul will cause recursion
 	generate
 		if (A_SIGNED && !B_SIGNED)
-			\$mul #(
+			\$__soft__mul #(
 				.A_SIGNED(A_SIGNED),
 				.B_SIGNED(1),
 				.A_WIDTH(A_WIDTH),
@@ -233,23 +233,23 @@ module _90_internal_mul_to_external (A, B, Y);
 				.Y_WIDTH(Y_WIDTH)
 			) _TECHMAP_REPLACE_ (
 				.A(A),
-				.B({1'b0, B}),
+				.B({1'b0,B}),
 				.Y(Y)
 			);
 		else if (!A_SIGNED && B_SIGNED)
-			\$mul #(
+			\$__soft_mul #(
 				.A_SIGNED(1),
 				.B_SIGNED(B_SIGNED),
 				.A_WIDTH(A_WIDTH+1),
 				.B_WIDTH(B_WIDTH),
 				.Y_WIDTH(Y_WIDTH)
 			) _TECHMAP_REPLACE_ (
-				.A({1'b0, A}),
+				.A({1'b0,A}),
 				.B(B),
 				.Y(Y)
 			);
 		else
-			\$mul #(
+			\$__soft_mul #(
 				.A_SIGNED(A_SIGNED),
 				.B_SIGNED(B_SIGNED),
 				.A_WIDTH(A_WIDTH),
diff --git a/techlibs/ice40/synth_ice40.cc b/techlibs/ice40/synth_ice40.cc
index 77bd0ac81..fcb177491 100644
--- a/techlibs/ice40/synth_ice40.cc
+++ b/techlibs/ice40/synth_ice40.cc
@@ -268,6 +268,7 @@ struct SynthIce40Pass : public ScriptPass
 			if (help_mode || dsp) {
 				run("techmap -map +/mul2dsp.v -D DSP_A_MAXWIDTH=16 -D DSP_B_MAXWIDTH=16 -D DSP_MINWIDTH=11 -D DSP_NAME=$__MUL16X16", "(if -dsp)");
 				run("ice40_dsp", "(if -dsp)");
+				run("chtype -set $mul t:$__soft_mul");
 			}
 			run("alumacc");
 			run("opt");
-- 
2.30.2