r300/compiler: Reorganize presub_helper()

diff --git a/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c b/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c
index 0c6b1bd720a04c7959eeb185fbda3f15b0f44193..c15a9b1c451c1ea28ecf7d35e04ba37e36751399 100644 (file)
--- a/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c
+++ b/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c
@@ -533,51 +533,45 @@ static int presub_helper(
        for(inst = s->Inst->Next; inst != &c->Program.Instructions;
                                                        inst = inst->Next) {
                unsigned int i;
+               unsigned char can_use_presub = 1;
                const struct rc_opcode_info * info =
                                        rc_get_opcode_info(inst->U.I.Opcode);
+               /* XXX: There are some situations where instructions
+                * with more than 2 src registers can use the
+                * presubtract select, but to keep things simple we
+                * will disable presubtract on these instructions for
+                * now. */
+               if (info->NumSrcRegs > 2 || info->HasTexture) {
+                       can_use_presub = 0;
+               }
+
+               /* We can't use more than one presubtract value in an
+                * instruction, unless the two prsubtract operations
+                * are the same and read from the same registers. */
+               if (inst->U.I.PreSub.Opcode != RC_PRESUB_NONE) {
+                       if (inst->U.I.PreSub.Opcode != presub_opcode
+                               || inst->U.I.PreSub.SrcReg[0].File !=
+                                       s->Inst->U.I.SrcReg[1].File
+                               || inst->U.I.PreSub.SrcReg[0].Index !=
+                                       s->Inst->U.I.SrcReg[1].Index) {
+                               can_use_presub = 0;
+                       }
+               }
 
+               /* Even if the instruction can't use a presubtract operation
+                * we still need to check if the instruction reads from
+                * s->Inst->U.I.DstReg, because if it does we must not
+                * remove s->Inst. */
                for(i = 0; i < info->NumSrcRegs; i++) {
                        if(s->Inst->U.I.DstReg.WriteMask !=
                                        src_reads_dst_mask(inst->U.I.SrcReg[i],
                                                s->Inst->U.I.DstReg)) {
                                continue;
                        }
-                       if (cant_sub) {
-                               can_remove = 0;
-                               break;
-                       }
-                       /* XXX: There are some situations where instructions
-                        * with more than 2 src registers can use the
-                        * presubtract select, but to keep things simple we
-                        * will disable presubtract on these instructions for
-                        * now. Note: This if statement should not be pulled
-                        * outside of the loop, because it only applies to
-                        * instructions that could potentially use the
-                        * presubtract source. */
-                       if (info->NumSrcRegs > 2) {
+                       if (cant_sub || !can_use_presub) {
                                can_remove = 0;
                                break;
                        }
-
-                       if (info->HasTexture) {
-                               can_remove = 0;
-                               break;
-                       }
-
-                       /* We can't use more than one presubtract value in an
-                        * instruction, unless the two prsubtract operations
-                        * are the same and read from the same registers. */
-                       if (inst->U.I.PreSub.Opcode != RC_PRESUB_NONE) {
-                               if (inst->U.I.PreSub.Opcode != presub_opcode
-                                       || inst->U.I.PreSub.SrcReg[0].File !=
-                                               s->Inst->U.I.SrcReg[1].File
-                                       || inst->U.I.PreSub.SrcReg[0].Index !=
-                                               s->Inst->U.I.SrcReg[1].Index) {
-
-                                       can_remove = 0;
-                                       break;
-                               }
-                       }
                        presub_replace(s, inst, i);
                        can_remove = 1;
                }