diff --git a/tests/arch/ice40/bug1626.ys b/tests/arch/ice40/bug1626.ys
new file mode 100644
index 000000000..27b6fb5e8
--- /dev/null
+++ b/tests/arch/ice40/bug1626.ys
@@ -0,0 +1,217 @@
+read_ilang <<EOT
+# Generated by Yosys 0.9+1706 (git sha1 58ab9f60, clang 6.0.0-1ubuntu2 -fPIC -Os)
+autoidx 2815
+attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:9"
+attribute \cells_not_processed 1
+attribute \dynports 1
+module \ahb_async_sram_halfwidth
+  parameter \DEPTH
+  parameter \W_ADDR
+  parameter \W_BYTEADDR
+  parameter \W_DATA
+  parameter \W_SRAM_ADDR
+  parameter \W_SRAM_DATA
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  wire $0\addr_lsb[0:0]
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  wire $0\hready_r[0:0]
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  wire $0\long_dphase[0:0]
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  wire width 16 $0\rdata_buf[15:0]
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  wire $0\read_dph[0:0]
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  wire $0\write_dph[0:0]
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:63"
+  wire width 32 $add$../hdl/mem/ahb_async_sram_halfwidth.v:63$2433_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:62"
+  wire width 16 $and$../hdl/mem/ahb_async_sram_halfwidth.v:62$2431_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:56"
+  wire $eq$../hdl/mem/ahb_async_sram_halfwidth.v:56$2424_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2450_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2451_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2452_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2453_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2454_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2455_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2456_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2457_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2458_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:112"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:112$2459_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:118"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:118$2444_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:133"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:133$2449_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:140"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:140$2461_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:140"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:140$2463_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:58"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:58$2425_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:59"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:59$2426_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:59"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:59$2427_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:59"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:59$2429_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:91"
+  wire $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:91$2441_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:104"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:104$2442_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:118"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:118$2443_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:125"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:125$2446_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:132"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:132$2447_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:59"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:59$2428_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:72"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:72$2437_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:81"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:81$2438_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:83"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:83$2439_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:91"
+  wire $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:91$2440_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:118"
+  wire $logic_or$../hdl/mem/ahb_async_sram_halfwidth.v:118$2445_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:132"
+  wire $logic_or$../hdl/mem/ahb_async_sram_halfwidth.v:132$2448_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:59"
+  wire $logic_or$../hdl/mem/ahb_async_sram_halfwidth.v:59$2430_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:139"
+  wire width 2 $not$../hdl/mem/ahb_async_sram_halfwidth.v:139$2460_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:139"
+  wire width 2 $not$../hdl/mem/ahb_async_sram_halfwidth.v:139$2462_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:54"
+  wire width 2 $not$../hdl/mem/ahb_async_sram_halfwidth.v:54$2421_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:63"
+  wire width 16 $shiftx$../hdl/mem/ahb_async_sram_halfwidth.v:63$2434_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:54"
+  wire width 8 $shl$../hdl/mem/ahb_async_sram_halfwidth.v:54$2419_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:54"
+  wire width 2 $shl$../hdl/mem/ahb_async_sram_halfwidth.v:54$2420_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:55"
+  wire width 2 $shl$../hdl/mem/ahb_async_sram_halfwidth.v:55$2422_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:56"
+  wire width 32 $shl$../hdl/mem/ahb_async_sram_halfwidth.v:56$2423_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:63"
+  wire width 32 $ternary$../hdl/mem/ahb_async_sram_halfwidth.v:63$2432_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:65"
+  wire width 16 $ternary$../hdl/mem/ahb_async_sram_halfwidth.v:65$2435_Y
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:50"
+  wire \addr_lsb
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:24"
+  wire width 32 \ahbls_haddr
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:28"
+  wire width 3 \ahbls_hburst
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:30"
+  wire \ahbls_hmastlock
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:29"
+  wire width 4 \ahbls_hprot
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:32"
+  wire width 32 \ahbls_hrdata
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:22"
+  wire \ahbls_hready
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:21"
+  wire \ahbls_hready_resp
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:23"
+  wire \ahbls_hresp
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:27"
+  wire width 3 \ahbls_hsize
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:26"
+  wire width 2 \ahbls_htrans
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:31"
+  wire width 32 \ahbls_hwdata
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:25"
+  wire \ahbls_hwrite
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:56"
+  wire \aphase_full_width
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:55"
+  wire width 2 \bytemask
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:54"
+  wire width 2 \bytemask_noshift
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:17"
+  wire \clk
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:46"
+  wire \hready_r
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:47"
+  wire \long_dphase
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:64"
+  wire width 16 \rdata_buf
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:49"
+  wire \read_dph
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:18"
+  wire \rst_n
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:34"
+  wire width 11 \sram_addr
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:39"
+  wire width 2 \sram_byte_n
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:36"
+  wire \sram_ce_n
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:35"
+  wire width 16 \sram_dq
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:38"
+  wire \sram_oe_n
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:61"
+  wire width 16 \sram_q
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:62"
+  wire width 16 \sram_rdata
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:63"
+  wire width 16 \sram_wdata
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:37"
+  wire \sram_we_n
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:58"
+  wire \we_next
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:48"
+  wire \write_dph
+  attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:71"
+  process $proc$../hdl/mem/ahb_async_sram_halfwidth.v:71$2436
+    attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:72"
+    switch $logic_not$../hdl/mem/ahb_async_sram_halfwidth.v:72$2437_Y
+      case 1'1
+      case 
+        attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:78"
+        switch \ahbls_hready
+          case 1'1
+            attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:79"
+            switch \ahbls_htrans [1]
+              case 1'1
+              case 
+            end
+          case 
+            attribute \src "../hdl/mem/ahb_async_sram_halfwidth.v:91"
+            switch $logic_and$../hdl/mem/ahb_async_sram_halfwidth.v:91$2441_Y
+              case 1'1
+              case 
+            end
+        end
+    end
+    sync posedge \clk
+    sync negedge \rst_n
+  end
+  connect \ahbls_hresp 1'0
+  connect \bytemask_noshift $not$../hdl/mem/ahb_async_sram_halfwidth.v:54$2421_Y
+  connect \bytemask $shl$../hdl/mem/ahb_async_sram_halfwidth.v:55$2422_Y
+  connect \aphase_full_width $eq$../hdl/mem/ahb_async_sram_halfwidth.v:56$2424_Y
+  connect \we_next $logic_or$../hdl/mem/ahb_async_sram_halfwidth.v:59$2430_Y
+  connect \sram_rdata $and$../hdl/mem/ahb_async_sram_halfwidth.v:62$2431_Y
+  connect \sram_wdata $shiftx$../hdl/mem/ahb_async_sram_halfwidth.v:63$2434_Y
+  connect \ahbls_hrdata { \sram_rdata $ternary$../hdl/mem/ahb_async_sram_halfwidth.v:65$2435_Y }
+  connect \ahbls_hready_resp \hready_r
+end
+EOT
+
+synth_ice40 -abc2 -abc9