diff mbox

[v4,2/5] sim: cgen: add MUL2OFSI and MUL1OFSI macros (needed for OR1K l.mul[u])

Message ID 700407e5797b8b9b9f76b2dba026d1b06978987b.1496066478.git.shorne@gmail.com
State New, archived
Headers

Commit Message

Stafford Horne May 29, 2017, 2:47 p.m. UTC 
  From: Peter Gavin <pgavin@gmail.com>

sim/common/ChangeLog:

2012-03-14  Peter Gavin  <pgavin@gmail.com>

	* cgen-ops.h (MUL2OFSI): New macro, 1's complement.
	(MUL1OFSI): New macro, 2's complement.
---
 sim/common/cgen-ops.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Comments

Simon Marchi Sept. 4, 2017, 8:32 p.m. UTC | #1 
> --- a/sim/common/cgen-ops.h
> +++ b/sim/common/cgen-ops.h
> @@ -631,6 +631,22 @@ SUBOFQI (QI a, QI b, BI c)
>    return res;
>  }
> 
> +SEMOPS_INLINE BI
> +MUL2OFSI (SI a, SI b)
> +{
> +  DI tmp = MULDI (EXTSIDI(a), EXTSIDI(b));
> +  BI res = tmp < -0x80000000LL || tmp > 0x7fffffffLL;
> +  return res;
> +}
> +
> +SEMOPS_INLINE BI
> +MUL1OFSI (USI a, USI b)
> +{
> +  UDI tmp = MULDI (ZEXTSIDI(a), ZEXTSIDI(b));
> +  BI res = (tmp > 0xFFFFFFFFULL);
> +  return res;
> +}

What are these functions expected to return?  They seem to return 1 when 
the result would overflow 32-bits, but just to be sure.

Simon
Stafford Horne Sept. 4, 2017, 9:05 p.m. UTC | #2 
On Tue, Sep 5, 2017 at 5:32 AM, Simon Marchi <simon.marchi@polymtl.ca> wrote:
>> --- a/sim/common/cgen-ops.h
>> +++ b/sim/common/cgen-ops.h
>> @@ -631,6 +631,22 @@ SUBOFQI (QI a, QI b, BI c)
>>    return res;
>>  }
>>
>> +SEMOPS_INLINE BI
>> +MUL2OFSI (SI a, SI b)
>> +{
>> +  DI tmp = MULDI (EXTSIDI(a), EXTSIDI(b));
>> +  BI res = tmp < -0x80000000LL || tmp > 0x7fffffffLL;
>> +  return res;
>> +}
>> +
>> +SEMOPS_INLINE BI
>> +MUL1OFSI (USI a, USI b)
>> +{
>> +  UDI tmp = MULDI (ZEXTSIDI(a), ZEXTSIDI(b));
>> +  BI res = (tmp > 0xFFFFFFFFULL);
>> +  return res;
>> +}
>
>
> What are these functions expected to return?  They seem to return 1 when the
> result would overflow 32-bits, but just to be sure.

They do just return 1 when there is overflow.

They are used in:
    cpu/or1korbis.cpu

To calculate the overflow and carry flags.

   ; 2's complement overflow
   (set sys-sr-ov (mul-o2flag WI rA (ext WI simm16)))
   ; 1's complement overflow
   (set sys-sr-cy (mul-o1flag UWI rA (ext UWI simm16)))

Thanks for pointing this out though the ChangeLog says "New macro, 1's
complement."  I think it should mention "New macro, 1's complement
_overflow_."
diff mbox

Patch

diff --git a/sim/common/cgen-ops.h b/sim/common/cgen-ops.h
index 97585d7..ffbdf3f 100644
--- a/sim/common/cgen-ops.h
+++ b/sim/common/cgen-ops.h
@@ -631,6 +631,22 @@  SUBOFQI (QI a, QI b, BI c)
   return res;
 }
 
+SEMOPS_INLINE BI
+MUL2OFSI (SI a, SI b)
+{
+  DI tmp = MULDI (EXTSIDI(a), EXTSIDI(b));
+  BI res = tmp < -0x80000000LL || tmp > 0x7fffffffLL;
+  return res;
+}
+
+SEMOPS_INLINE BI
+MUL1OFSI (USI a, USI b)
+{
+  UDI tmp = MULDI (ZEXTSIDI(a), ZEXTSIDI(b));
+  BI res = (tmp > 0xFFFFFFFFULL);
+  return res;
+}
+
 #else
 
 SI ADDCSI (SI, SI, BI);
@@ -651,6 +667,8 @@  UBI ADDOFQI (QI, QI, BI);
 QI SUBCQI (QI, QI, BI);
 UBI SUBCFQI (QI, QI, BI);
 UBI SUBOFQI (QI, QI, BI);
+BI MUL1OFSI (SI a, SI b);
+BI MUL2OFSI (SI a, SI b);
 
 #endif