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i965: Avoid moving the current value back into the accumulator for MAD.

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This is a 2.9% (+/-.3%) performance win for my GL demo, which hits MAD
sequences for matrix transforms.
This commit is contained in:
Eric Anholt 2009-11-11 11:58:12 -08:00
parent d6690ce15f
commit 91bd593109
1 changed files with 34 additions and 1 deletions
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35
src/mesa/drivers/dri/i965/brw_vs_emit.c
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@ -1271,6 +1271,38 @@ post_vs_emit( struct brw_vs_compile *c,
}
}
static GLboolean
accumulator_contains(struct brw_vs_compile *c, struct brw_reg val)
{
struct brw_compile *p = &c->func;
struct brw_instruction *prev_insn = &p->store[p->nr_insn - 1];
if (p->nr_insn == 0)
return GL_FALSE;
if (val.address_mode != BRW_ADDRESS_DIRECT)
return GL_FALSE;
switch (prev_insn->header.opcode) {
case BRW_OPCODE_MOV:
case BRW_OPCODE_MAC:
case BRW_OPCODE_MUL:
if (prev_insn->header.access_mode == BRW_ALIGN_16 &&
prev_insn->header.execution_size == val.width &&
prev_insn->bits1.da1.dest_reg_file == val.file &&
prev_insn->bits1.da1.dest_reg_type == val.type &&
prev_insn->bits1.da1.dest_address_mode == val.address_mode &&
prev_insn->bits1.da1.dest_reg_nr == val.nr &&
prev_insn->bits1.da16.dest_subreg_nr == val.subnr / 16 &&
prev_insn->bits1.da16.dest_writemask == 0xf)
return GL_TRUE;
else
return GL_FALSE;
default:
return GL_FALSE;
}
}
static uint32_t
get_predicate(const struct prog_instruction *inst)
{
@ -1449,7 +1481,8 @@ void brw_vs_emit(struct brw_vs_compile *c )
unalias3(c, dst, args[0], args[1], args[2], emit_lrp_noalias);
break;
case OPCODE_MAD:
brw_MOV(p, brw_acc_reg(), args[2]);
if (!accumulator_contains(c, args[2]))
brw_MOV(p, brw_acc_reg(), args[2]);
brw_MAC(p, dst, args[0], args[1]);
break;
case OPCODE_MAX: