nv50/ir: change the way float face is returned

The old way made it impossible for the optimizer to reason about what
was going on. The new way is the same number of instructions (the neg
gets folded into the cvt) but enables the optimizer to be cleverer if
comparing to a constant (most common case). [The optimizer is presently
not sufficiently clever to work this out, but it could relatively easily
be made to be. The old way would have required significant complexity to
work out.]

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nv50.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nv50.cpp
index 0d7612efe65d92a21fcb15655ebebf46b69a6f0d..1ad086094dc0ab181edef5aeb317518fd3007adf 100644 (file)
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nv50.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nv50.cpp
@@ -1094,8 +1094,9 @@ NV50LoweringPreSSA::handleRDSV(Instruction *i)
    case SV_FACE:
       bld.mkInterp(NV50_IR_INTERP_FLAT, def, addr, NULL);
       if (i->dType == TYPE_F32) {
-         bld.mkOp2(OP_AND, TYPE_U32, def, def, bld.mkImm(0x80000000));
-         bld.mkOp2(OP_XOR, TYPE_U32, def, def, bld.mkImm(0xbf800000));
+         bld.mkOp2(OP_OR, TYPE_U32, def, def, bld.mkImm(0x00000001));
+         bld.mkOp1(OP_NEG, TYPE_S32, def, def);
+         bld.mkCvt(OP_CVT, TYPE_F32, def, TYPE_S32, def);
       }
       break;
    case SV_NCTAID:

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
index c2341317b1ad6954a48a65ec345b4a9eba4e9e69..5dfb77745a6080a72ff58acda02446e06dc8abe9 100644 (file)
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
@@ -1454,8 +1454,9 @@ NVC0LoweringPass::handleRDSV(Instruction *i)
       Value *face = i->getDef(0);
       bld.mkInterp(NV50_IR_INTERP_FLAT, face, addr, NULL);
       if (i->dType == TYPE_F32) {
-         bld.mkOp2(OP_AND, TYPE_U32, face, face, bld.mkImm(0x80000000));
-         bld.mkOp2(OP_XOR, TYPE_U32, face, face, bld.mkImm(0xbf800000));
+         bld.mkOp2(OP_OR, TYPE_U32, face, face, bld.mkImm(0x00000001));
+         bld.mkOp1(OP_NEG, TYPE_S32, face, face);
+         bld.mkCvt(OP_CVT, TYPE_F32, face, TYPE_S32, face);
       }
    }
       break;