X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=src%2Fsoc%2Ffu%2Fcommon_output_stage.py;h=cc0f00a38063df1ee54b3dfdd2c1cbf758b3bf3a;hb=8af9ff71c838cea18b6287a3d81958de877c5958;hp=1a28956f30bb951be7aa0dee72b17d097be5b54b;hpb=396550dfe068f8ed21c584f3c364dd0b0ce38151;p=soc.git

diff --git a/src/soc/fu/common_output_stage.py b/src/soc/fu/common_output_stage.py
index 1a28956f..cc0f00a3 100644
--- a/src/soc/fu/common_output_stage.py
+++ b/src/soc/fu/common_output_stage.py
@@ -1,9 +1,9 @@
 # This stage is intended to handle the gating of carry out,
 # and updating the condition register
-from nmigen import (Module, Signal, Cat, Repl)
+from nmigen import (Module, Signal, Cat, Const)
 from nmutil.pipemodbase import PipeModBase
 from ieee754.part.partsig import PartitionedSignal
-from soc.decoder.power_enums import InternalOp
+from soc.decoder.power_enums import MicrOp
 
 
 class CommonOutputStage(PipeModBase):
@@ -14,35 +14,45 @@ class CommonOutputStage(PipeModBase):
         m = Module()
         comb = m.d.comb
         op = self.i.ctx.op
+        if hasattr(self.o, "xer_so"):
+            xer_so_o = self.o.xer_so.data[0]
+        else:
+            xer_so_o = Const(0, 1)
 
-        # op requests inversion of the output
+        # op requests inversion of the output...
         o = Signal.like(self.i.o)
-        if hasattr(op, "invert_out"):
+        if hasattr(op, "invert_out"): # ... optionally
             with m.If(op.invert_out):
                 comb += o.eq(~self.i.o.data)
             with m.Else():
                 comb += o.eq(self.i.o.data)
         else:
-                comb += o.eq(self.i.o.data)
+            comb += o.eq(self.i.o.data) # ... no inversion
 
         # target register if 32-bit is only the 32 LSBs
+        # XXX ah.  right.  this needs to be done only if the *mode* is 32-bit
+        # see https://bugs.libre-soc.org/show_bug.cgi?id=424
         target = Signal(64, reset_less=True)
-        with m.If(op.is_32bit):
-            comb += target.eq(o[:32])
-        with m.Else():
-            comb += target.eq(o)
+        #with m.If(op.is_32bit):
+        #    comb += target.eq(o[:32])
+        #with m.Else():
+        #    comb += target.eq(o)
+        comb += target.eq(o)
 
-        # Handle carry_out
-        comb += self.o.xer_ca.data.eq(self.i.xer_ca.data)
-        comb += self.o.xer_ca.ok.eq(op.output_carry)
+        # carry-out only if actually present in this input spec
+        # (note: MUL and DIV do not have it, but ALU and Logical do)
+        if hasattr(self.i, "xer_ca"):
+            # Handle carry_out
+            comb += self.o.xer_ca.data.eq(self.i.xer_ca.data)
+            comb += self.o.xer_ca.ok.eq(op.output_carry)
 
         # create condition register cr0 and sticky-overflow
         is_nzero = Signal(reset_less=True)
         is_positive = Signal(reset_less=True)
         is_negative = Signal(reset_less=True)
         msb_test = Signal(reset_less=True) # set equal to MSB, invert if OP=CMP
-        is_cmp = Signal(reset_less=True)   # true if OP=CMP
-        is_cmpeqb = Signal(reset_less=True)   # true if OP=CMP
+        is_cmp = Signal(reset_less=True)     # true if OP=CMP
+        is_cmpeqb = Signal(reset_less=True)  # true if OP=CMPEQB
         self.so = Signal(1, reset_less=True)
         cr0 = Signal(4, reset_less=True)
 
@@ -50,24 +60,34 @@ class CommonOutputStage(PipeModBase):
         # that can be used as a test of whether to invert the +ve/-ve test
         # see https://bugs.libre-soc.org/show_bug.cgi?id=305#c60
 
-        comb += is_cmp.eq(op.insn_type == InternalOp.OP_CMP)
-        comb += is_cmpeqb.eq(op.insn_type == InternalOp.OP_CMPEQB)
-        comb += msb_test.eq(target[-1] ^ is_cmp)
+        comb += is_cmp.eq(op.insn_type == MicrOp.OP_CMP)
+        comb += is_cmpeqb.eq(op.insn_type == MicrOp.OP_CMPEQB)
+        # nope - if *processor* mode is 32-bit
+        #with m.If(op.is_32bit):
+        #    comb += msb_test.eq(target[-1] ^ is_cmp) # 64-bit MSB
+        #with m.Else():
+        #    comb += msb_test.eq(target[31] ^ is_cmp) # 32-bit MSB
+        comb += msb_test.eq(target[-1]) # 64-bit MSB
         comb += is_nzero.eq(target.bool())
-        comb += is_positive.eq(is_nzero & ~msb_test)
-        comb += is_negative.eq(is_nzero & msb_test)
+        with m.If(is_cmp): # invert pos/neg tests
+            comb += is_positive.eq(msb_test)
+            comb += is_negative.eq(is_nzero & ~msb_test)
+        with m.Else():
+            comb += is_negative.eq(msb_test)
+            comb += is_positive.eq(is_nzero & ~msb_test)
 
         with m.If(is_cmpeqb):
             comb += cr0.eq(self.i.cr0.data)
         with m.Else():
-            comb += cr0.eq(Cat(self.so, ~is_nzero, is_positive, is_negative))
+            comb += cr0.eq(Cat(xer_so_o, ~is_nzero, is_positive, is_negative))
 
-        # copy out [inverted] cr0, output, and context out
+        # copy out [inverted?] output, cr0, and context out
         comb += self.o.o.data.eq(o)
         comb += self.o.o.ok.eq(self.i.o.ok)
-        comb += self.o.cr0.data.eq(cr0)
-        comb += self.o.cr0.ok.eq(op.write_cr.ok)
         # CR0 to be set
+        comb += self.o.cr0.data.eq(cr0)
+        comb += self.o.cr0.ok.eq(op.write_cr0)
+        # context
         comb += self.o.ctx.eq(self.i.ctx)
 
         return m