r300/compiler: Fix two mistakes in the presubtract optimization pass.

1. We can't turn an instruction into a presubtract operation if it
writes to one of the registers it reads from.
2. If we turn an instruction into a presubtract operation, we can't
remove that intruction unless all readers can use the presubtract
operation.

This fixes fdo bug 30337.
This is a candidate for the 7.9 branch.

diff --git a/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c b/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c
index c15a9b1c451c1ea28ecf7d35e04ba37e36751399..e2889302e6950ed3415755406bfca44a83774e13 100644 (file)
--- a/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c
+++ b/src/mesa/drivers/dri/r300/compiler/radeon_optimize.c
@@ -475,8 +475,8 @@ static void constant_folding(struct radeon_compiler * c, struct rc_instruction *
 }
 
 /**
- * This function returns a writemask that indicates wich components are
- * read by src and also written by dst.
+ * If src and dst use the same register, this function returns a writemask that
+ * indicates wich components are read by src.  Otherwise zero is returned.
  */
 static unsigned int src_reads_dst_mask(struct rc_src_register src,
                                                struct rc_dst_register dst)
@@ -563,10 +563,18 @@ static int presub_helper(
                 * 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;
+                       unsigned int mask = src_reads_dst_mask(
+                               inst->U.I.SrcReg[i], s->Inst->U.I.DstReg);
+                       /* XXX We could be more aggressive here using
+                        * presubtract.  It is okay if SrcReg[i] only reads
+                        * from some of the mask components. */
+                       if(s->Inst->U.I.DstReg.WriteMask != mask) {
+                               if (s->Inst->U.I.DstReg.WriteMask & mask) {
+                                       can_remove = 0;
+                                       break;
+                               } else {
+                                       continue;
+                               }
                        }
                        if (cant_sub || !can_use_presub) {
                                can_remove = 0;
@@ -626,6 +634,21 @@ static void presub_replace_add(struct peephole_state *s,
        inst->U.I.SrcReg[src_index].Index = presub_opcode;
 }
 
+static int is_presub_candidate(struct rc_instruction * inst)
+{
+       const struct rc_opcode_info * info = rc_get_opcode_info(inst->U.I.Opcode);
+       unsigned int i;
+
+       if (inst->U.I.PreSub.Opcode != RC_PRESUB_NONE || inst->U.I.SaturateMode)
+               return 0;
+
+       for(i = 0; i < info->NumSrcRegs; i++) {
+               if (src_reads_dst_mask(inst->U.I.SrcReg[i], inst->U.I.DstReg))
+                       return 0;
+       }
+       return 1;
+}
+
 static int peephole_add_presub_add(
        struct radeon_compiler * c,
        struct rc_instruction * inst_add)
@@ -635,10 +658,7 @@ static int peephole_add_presub_add(
        unsigned int i;
        struct peephole_state s;
 
-       if (inst_add->U.I.PreSub.Opcode != RC_PRESUB_NONE)
-               return 0;
-
-       if (inst_add->U.I.SaturateMode)
+       if (!is_presub_candidate(inst_add))
                return 0;
 
        if (inst_add->U.I.SrcReg[0].Swizzle != inst_add->U.I.SrcReg[1].Swizzle)
@@ -705,10 +725,7 @@ static int peephole_add_presub_inv(
        unsigned int i, swz, mask;
        struct peephole_state s;
 
-       if (inst_add->U.I.PreSub.Opcode != RC_PRESUB_NONE)
-               return 0;
-
-       if (inst_add->U.I.SaturateMode)
+       if (!is_presub_candidate(inst_add))
                return 0;
 
        mask = inst_add->U.I.DstReg.WriteMask;