Re: patch to stop GCC from shifting by a negative number

[Steve Ellcey <sje@cup.hp.com>]

> +  /* You want to truncate to a _what_?  */
> +  if (GET_MODE_CLASS (mode) != MODE_INT
> +      && GET_MODE_CLASS (mode) != MODE_PARTIAL_INT)
> +    abort ();
> +

I ran the test suite with your patch and hit this abort a couple of
times on the PA64 HP-UX platform with tests
gcc.c-torture/execute/20020227-1.c and gcc.c-torture/compile/simd-1.c
using -O2 optmization.

In 20020227-1.c I enter simplify_binary_operation
with

code=LSHIFTRT
mode=SCmode
op0=(const_int -1 [0xffffffffffffffff])
op1=(const_int 32 [0x20])

In simd-1.c I enter simplify_binary_operation
with

code=ASHIFT
mode=V2SImode
op0=(const_int 4294967295 [0xffffffff])
op1=(const_int 32 [0x20])

and in both cases I call trunc_int_for_mode right at the end of
simplify_binary_operation with a mode of either SCmode or V2SImode which
then causes the abort to be hit.

Any ideas on what a good fix for these cases would be?

Steve Ellcey
sje@cup.hp.com