Armv7m: Allow subs with immediate and two registers

example.py

@@ -704,6 +704,9 @@ def __init__(self, var="", arch=Arch_Armv7M, target=Target_CortexM7):
     def core(self,slothy):
         slothy.config.variable_size=True
         slothy.optimize_loop("start", forced_loop_type=Arch_Armv7M.SubsLoop)
+        slothy.config.sw_pipelining.enabled = True
+        slothy.config.outputs = ["r0", "r1", "r2", "r5", "flags"]
+        slothy.optimize_loop("start2", forced_loop_type=Arch_Armv7M.BranchLoop)
 
 class Armv7mLoopCmp(Example):
     def __init__(self, var="", arch=Arch_Armv7M, target=Target_CortexM7):

examples/naive/armv7m/loop_subs.s

@@ -1,4 +1,12 @@
 movw r5, #16
 start:
     subs.w r5, #1
-    bne.w start
+    bne.w start
+
+movw r5, #16
+start2:
+    eor.w r0, r0, r7
+    mul r1, r0, r8
+    eor.w r0, r1, r4
+    subs.w r5, r5, #1
+    bne.w start2

examples/opt/armv7m/loop_subs_opt_m7.s

@@ -1,11 +1,55 @@
 movw r5, #16
 start:
+                // Instructions:    0
+                // Expected cycles: 0
+                // Expected IPC:    0.00
+                //
+                // Wall time:     0.02s
+                // User time:     0.02s
+                //
+        subs r5, #1
+        bne start
+
+movw r5, #16
                 // Instructions:    0
                 // Expected cycles: 0
                 // Expected IPC:    0.00
                 //
                 // Wall time:     0.00s
                 // User time:     0.00s
                 //
-        subs r5, #1
-        bne start
+start2:
+                                 // Instructions:    4
+                                 // Expected cycles: 4
+                                 // Expected IPC:    1.00
+                                 //
+                                 // Cycle bound:     2.0
+                                 // IPC bound:       2.00
+                                 //
+                                 // Wall time:     0.03s
+                                 // User time:     0.03s
+                                 //
+                                 // ----- cycle (expected) ------>
+                                 // 0                        25
+                                 // |------------------------|----
+        subs.w r5, r5, #1        // *.............................
+        eor.w r0, r0, r7         // *.............................
+        mul r1, r0, r8           // .*............................
+        eor.w r0, r1, r4         // ...*..........................
+
+                                  // ------ cycle (expected) ------>
+                                  // 0                        25
+                                  // |------------------------|-----
+        // eor.w r0, r0, r7       // *...~...~...~...~...~...~...~..
+        // mul r1, r0, r8         // .*..'~..'~..'~..'~..'~..'~..'~.
+        // eor.w r0, r1, r4       // ...*'..~'..~'..~'..~'..~'..~'..
+        // subs.w r5, r5, #1      // *...~...~...~...~...~...~...~..
+
+        bne start2
+                // Instructions:    0
+                // Expected cycles: 0
+                // Expected IPC:    0.00
+                //
+                // Wall time:     0.00s
+                // User time:     0.00s
+                //

slothy/targets/arm_v7m/arch_v7m.py

@@ -338,6 +338,10 @@ def start(self, loop_cnt, indentation=0, fixup=0, unroll=1, jump_if_empty=None,
                 loop_cnt_reg = inst[0].args_in_out[0]
                 loop_end_reg = inst[0].args_in_out[0]
                 break
+            elif isinstance(inst[0], subs_imm):
+                loop_cnt_reg = inst[0].args_out[0]
+                loop_end_reg = inst[0].args_out[0]
+                break
 
         # Find FPR that is used to stash the loop end incase it's vmov loop
         loop_end_reg_fpr = None
@@ -1215,6 +1219,12 @@ class sub_imm_short(Armv7mBasicArithmetic): # pylint: disable=missing-docstring,
     pattern = "sub<width> <Ra>, <imm>"
     in_outs = ["Ra"]
 
+class subs_imm(Armv7mBasicArithmetic): # pylint: disable=missing-docstring,invalid-name
+    pattern = "subs<width> <Rd>, <Ra>, <imm>"
+    inputs = ["Ra"]
+    outputs = ["Rd"]
+    modifiesFlags = True
+
 class subs_imm_short(Armv7mBasicArithmetic): # pylint: disable=missing-docstring,invalid-name
     pattern = "subs<width> <Ra>, <imm>"
     in_outs = ["Ra"]

slothy/targets/arm_v7m/cortex_m7.py

@@ -143,7 +143,7 @@ def get_min_max_objective(slothy):
         add_short,
         add_imm,
         add_imm_short,
-        sub, subs_imm_short, sub_imm_short,
+        sub, subs_imm, subs_imm_short, sub_imm_short,
         neg_short,
         log_and,
         log_or,
@@ -185,6 +185,7 @@ def get_min_max_objective(slothy):
         add_shifted,
         sub_shifted,
         sub_imm_short,
+        subs_imm,
         subs_imm_short,
         uadd16, sadd16, usub16, ssub16,
         mul, mul_short,
@@ -228,6 +229,7 @@ def get_min_max_objective(slothy):
         add_shifted,
         sub_shifted,
         sub_imm_short,
+        subs_imm,
         subs_imm_short,
         uadd16, sadd16, usub16, ssub16,
         neg_short,