| Message ID | 1374534309.3633.96.camel@gnopaine |
|---|---|
| State | New |
| Headers | show |
On Mon, Jul 22, 2013 at 7:05 PM, Bill Schmidt <wschmidt@linux.vnet.ibm.com> wrote: > This patch is another fix for vector handling in little endian mode. > The first two operands for a pack pattern are two vector registers that > form a contiguous array of inputs. In LE mode the order of the operands > must be reversed so that the array remains contiguous in the reverse > order. > > This fixes a failure in the testsuite when run little-endian > (gcc.dg/vect/no-scevccp-outer-18.c). Bootstrapped and tested big-endian > on powerpc64-unknown-linux-gnu with no new regressions. Ok for trunk? > > Patch by Anton Blanchard. > > Thanks, > Bill > > > 2013-07-22 Bill Schmidt <wschmidt@linux.vnet.ibm.com> > Anton Blanchard <anton@au1.ibm.com> > > * config/rs6000/rs6000.c (altivec_expand_vec_perm_const): Reverse > two operands for little-endian. Wouldn't it be better to handle this where the code is performing a swap a few lines above? Thanks, David
On Mon, 2013-07-22 at 19:49 -0400, David Edelsohn wrote: > On Mon, Jul 22, 2013 at 7:05 PM, Bill Schmidt > <wschmidt@linux.vnet.ibm.com> wrote: > > This patch is another fix for vector handling in little endian mode. > > The first two operands for a pack pattern are two vector registers that > > form a contiguous array of inputs. In LE mode the order of the operands > > must be reversed so that the array remains contiguous in the reverse > > order. > > > > This fixes a failure in the testsuite when run little-endian > > (gcc.dg/vect/no-scevccp-outer-18.c). Bootstrapped and tested big-endian > > on powerpc64-unknown-linux-gnu with no new regressions. Ok for trunk? > > > > Patch by Anton Blanchard. > > > > Thanks, > > Bill > > > > > > 2013-07-22 Bill Schmidt <wschmidt@linux.vnet.ibm.com> > > Anton Blanchard <anton@au1.ibm.com> > > > > * config/rs6000/rs6000.c (altivec_expand_vec_perm_const): Reverse > > two operands for little-endian. > > Wouldn't it be better to handle this where the code is performing a > swap a few lines above? Hm, I don't think so. The reason for that swap has nothing to do with endianness, so I think it would just confuse matters. Also there's a three-way swap going on with x, op0, and op1 there, and we just want to swap op0 and op1. I think the patch as it stands is probably easier to grok. Thanks, Bill > > Thanks, David >
On Mon, 2013-07-22 at 19:56 -0500, Bill Schmidt wrote: > > On Mon, 2013-07-22 at 19:49 -0400, David Edelsohn wrote: > > On Mon, Jul 22, 2013 at 7:05 PM, Bill Schmidt > > <wschmidt@linux.vnet.ibm.com> wrote: > > > This patch is another fix for vector handling in little endian mode. > > > The first two operands for a pack pattern are two vector registers that > > > form a contiguous array of inputs. In LE mode the order of the operands > > > must be reversed so that the array remains contiguous in the reverse > > > order. > > > > > > This fixes a failure in the testsuite when run little-endian > > > (gcc.dg/vect/no-scevccp-outer-18.c). Bootstrapped and tested big-endian > > > on powerpc64-unknown-linux-gnu with no new regressions. Ok for trunk? > > > > > > Patch by Anton Blanchard. > > > > > > Thanks, > > > Bill > > > > > > > > > 2013-07-22 Bill Schmidt <wschmidt@linux.vnet.ibm.com> > > > Anton Blanchard <anton@au1.ibm.com> > > > > > > * config/rs6000/rs6000.c (altivec_expand_vec_perm_const): Reverse > > > two operands for little-endian. > > > > Wouldn't it be better to handle this where the code is performing a > > swap a few lines above? > > Hm, I don't think so. The reason for that swap has nothing to do with > endianness, so I think it would just confuse matters. Also there's a > three-way swap going on with x, op0, and op1 there, and we just want to > swap op0 and op1. I think the patch as it stands is probably easier to > grok. Bleah, sorry, wasn't paying enough attention. Didn't notice x was being reused as an intermediate there instead of its regular use. It still seems a bit confusing to mix the two reasons for swapping, but I'll look at it. Thanks, Bill > > Thanks, > Bill > > > > Thanks, David > >
Index: gcc/config/rs6000/rs6000.c =================================================================== --- gcc/config/rs6000/rs6000.c (revision 201131) +++ gcc/config/rs6000/rs6000.c (working copy) @@ -28526,7 +28529,12 @@ altivec_expand_vec_perm_const (rtx operands[4]) x = target; else x = gen_reg_rtx (omode); - emit_insn (GEN_FCN (icode) (x, op0, op1)); + /* For little-endian, the two input operands must be swapped + to ensure proper right-to-left numbering from 0 to 2N-1. */ + if (BYTES_BIG_ENDIAN) + emit_insn (GEN_FCN (icode) (x, op0, op1)); + else + emit_insn (GEN_FCN (icode) (x, op1, op0)); if (omode != V16QImode) emit_move_insn (target, gen_lowpart (V16QImode, x)); return true;