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nv50/ir: add optimization for modulo by a non-power-of-2 value 

We can still use the optimized division methods which make use of
multiplication with overflow.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
This commit is contained in:
Ilia Mirkin 2017-11-10 22:10:46 -05:00
parent 3079993727
commit 50e913b9c5
1 changed files with 15 additions and 0 deletions
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15
src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
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@ -1192,6 +1192,21 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
delete_Instruction(prog, i);
}
} else if (s == 1) {
// In this case, we still want the optimized lowering that we get
// from having division by an immediate.
//
// a % b == a - (a/b) * b
bld.setPosition(i, false);
Value *div = bld.mkOp2v(OP_DIV, i->sType, bld.getSSA(),
i->getSrc(0), i->getSrc(1));
newi = bld.mkOp2(OP_ADD, i->sType, i->getDef(0), i->getSrc(0),
bld.mkOp2v(OP_MUL, i->sType, bld.getSSA(), div, i->getSrc(1)));
// TODO: Check that target supports this. In this case, we know that
// all backends do.
newi->src(1).mod = Modifier(NV50_IR_MOD_NEG);
delete_Instruction(prog, i);
}
break;