fix dual-instruction jumps with immediate values

This was a previously untested and incorrectly handled case. There
was already some offset manipulation to account for the extra
instructions for handling non-native conditions.

Because of the way symbol offsets are calculated by py-esp32-ulp,
namely that extra instructions are already included in the offsets,
the relative distance to a forward lying label is 1 instruction too
much. Or put another way, when expanding a jump into 2 instructions
the "current offset" refers to the first instruction, while it's
only the second instruction that jumps to the intended label, so
that difference must be accounted for.

Thus, for symbols we need to always subtract 1 from the offset. For
immediate values, we only subtract 1 for a backward jump.

Author: wnienhaus

esp32_ulp/opcodes.py

@@ -342,9 +342,9 @@ def get_rel(arg):
     if arg.type == IMM:
         if arg.value & 3 != 0:  # bitwise version of: arg.value % 4 != 0
             raise ValueError('Relative offset must be a multiple of 4')
-        return arg.value >> 2  # bitwise version of: arg.value // 4
+        return IMM, arg.value >> 2  # bitwise version of: arg.value // 4
     if arg.type == SYM:
-        return symbols.resolve_relative(arg.value)
+        return SYM, symbols.resolve_relative(arg.value)
     raise TypeError('wanted: immediate, got: %s' % arg.raw)
 
 
@@ -652,7 +652,7 @@ def _jump_relr(threshold, cond, offset):
 
 
 def i_jumpr(offset, threshold, condition):
-    offset = get_rel(offset)
+    offset_type, offset = get_rel(offset)
     threshold = get_imm(threshold)
     condition = get_cond(condition)
     if condition == 'lt':
@@ -669,7 +669,11 @@ def i_jumpr(offset, threshold, condition):
         # jump over next JUMPR
         skip_ins = _jump_relr(threshold + 1, BRCOND_GE, 2)
         # jump to target
-        offset -= 1  # adjust for the additional JUMPR instruction
+        if (offset_type == IMM and offset < 0) or offset_type == SYM:
+            # adjust for the additional JUMPR instruction
+            # for IMM offsets, the offset is relative to the 2nd instruction, so only backwards jumps need adjusting
+            # for SYM offsets, label offsets already include the extra instruction, so both directions need adjusting
+            offset -= 1
         jump_ins = _jump_relr(threshold, BRCOND_GE, offset)
         return (skip_ins, jump_ins)
     else:
@@ -691,7 +695,7 @@ def _jump_rels(threshold, cond, offset):
 
 
 def i_jumps(offset, threshold, condition):
-    offset = get_rel(offset)
+    offset_type, offset = get_rel(offset)
     threshold = get_imm(threshold)
     condition = get_cond(condition)
     if condition == 'lt':
@@ -711,7 +715,11 @@ def i_jumps(offset, threshold, condition):
         # jump over next JUMPS
         skip_ins = _jump_rels(threshold, skip_cond, 2)
         # jump to target
-        offset -= 1  # adjust for the additional JUMPS instruction
+        if (offset_type == IMM and offset < 0) or offset_type == SYM:
+            # adjust for the additional JUMPS instruction
+            # for IMM offsets, the offset is relative to the 2nd instruction, so only backwards jumps need adjusting
+            # for SYM offsets, label offsets already include the extra instruction, so both directions need adjusting
+            offset -= 1
         jump_ins = _jump_rels(threshold, jump_cond, offset)
 
         return (skip_ins, jump_ins)

tests/compat/jumps.S

@@ -26,12 +26,15 @@ entry:
 
   # jumps with immediate offset (specified in bytes, but real instruction uses words)
   jumps 0, 42, lt
+  jumps 0, 42, eq  #dual-instruction condition
 
   jumps 4, 42, lt
+  jumps 4, 42, eq  #dual-instruction condition
   jumps 8, 42, lt
   jumps 32, 42, lt
 
   jumps -4, 42, lt
+  jumps -4, 42, eq  #dual-instruction condition
   jumps -8, 42, lt
   jumps -32, 42, lt
 
@@ -52,12 +55,15 @@ entry:
 
   # jumpr with immediate offset (specified in bytes, but real instruction uses words)
   jumpr 0, 42, lt
+  jumpr 0, 42, eq  #dual-instruction condition
 
   jumpr 4, 42, lt
+  jumpr 4, 42, eq  #dual-instruction condition
   jumpr 8, 42, lt
   jumpr 32, 42, lt
 
   jumpr -4, 42, lt
+  jumpr -4, 42, eq  #dual-instruction condition
   jumpr -8, 42, lt
   jumpr -32, 42, lt