freedreno/ir3: cleanup double cmps.s from frontend

Since we cannot mov into a predicate register, the frontend uses a
'cmps.s p0.x, cond, 0' as a stand-in for mov to p0.x.  It does this
since it has no way to know that the source cond instruction (ie.
for a kill, br, etc) will only be used to write the predicate reg.
Detect this, and re-write the instruction writing p0.x to skip the
original cmps.[sfu].  (It is done like this, rather than re-writing
the dest of the first cmps.[sfu] in case the first cmps.[sfu]
actually has other users.)

Signed-off-by: Rob Clark <robclark@freedesktop.org>

diff --git a/src/gallium/drivers/freedreno/ir3/ir3_cp.c b/src/gallium/drivers/freedreno/ir3/ir3_cp.c
index 6037becf22f9a6ea302a9b91c14ffc49c3f57e21..e8a2f099391f9e2dcbadf3ba6edcc2cceb184ead 100644 (file)
--- a/src/gallium/drivers/freedreno/ir3/ir3_cp.c
+++ b/src/gallium/drivers/freedreno/ir3/ir3_cp.c
@@ -442,6 +442,37 @@ instr_cp(struct ir3_instruction *instr)
                instr_cp(instr->address);
                ir3_instr_set_address(instr, eliminate_output_mov(instr->address));
        }
+
+       /* we can end up with extra cmps.s from frontend, which uses a
+        *
+        *    cmps.s p0.x, cond, 0
+        *
+        * as a way to mov into the predicate register.  But frequently 'cond'
+        * is itself a cmps.s/cmps.f/cmps.u.  So detect this special case and
+        * just re-write the instruction writing predicate register to get rid
+        * of the double cmps.
+        */
+       if ((instr->opc == OPC_CMPS_S) &&
+                       (instr->regs[0]->num == regid(REG_P0, 0)) &&
+                       ssa(instr->regs[1]) &&
+                       (instr->regs[2]->flags & IR3_REG_IMMED) &&
+                       (instr->regs[2]->iim_val == 0)) {
+               struct ir3_instruction *cond = ssa(instr->regs[1]);
+               switch (cond->opc) {
+               case OPC_CMPS_S:
+               case OPC_CMPS_F:
+               case OPC_CMPS_U:
+                       instr->opc   = cond->opc;
+                       instr->flags = cond->flags;
+                       instr->cat2  = cond->cat2;
+                       instr->address = cond->address;
+                       instr->regs[1] = cond->regs[1];
+                       instr->regs[2] = cond->regs[2];
+                       break;
+               default:
+                       break;
+               }
+       }
 }
 
 void