tgsi: added tgsi_check_soa_dependencies() and related debug code (disabled)

The TGSI interpeter operates in SOA style.  We need to check for data
dependencies in instructions which read from and write to the same register.
For now just adding some debug code to detect that condition.  Actual fixes
to follow.

src/gallium/auxiliary/tgsi/tgsi_exec.c

@@ -53,6 +53,7 @@
 #include "pipe/p_compiler.h"
 #include "pipe/p_state.h"
 #include "pipe/p_shader_tokens.h"
+#include "tgsi/tgsi_dump.h"
 #include "tgsi/tgsi_parse.h"
 #include "tgsi/tgsi_util.h"
 #include "tgsi_exec.h"
@@ -169,6 +170,56 @@ print_temp(const struct tgsi_exec_machine *mach, uint index)
 #endif
 
 
+/**
+ * Check if there's a potential src/dst register data dependency when
+ * using SOA execution.
+ * Example:
+ *   MOV T, T.yxwz;
+ * This would expand into:
+ *   MOV t0, t1;
+ *   MOV t1, t0;
+ *   MOV t2, t3;
+ *   MOV t3, t2;
+ * The second instruction will have the wrong value for t0 if executed as-is.
+ */
+static boolean
+tgsi_check_soa_dependencies(const struct tgsi_full_instruction *inst)
+{
+   uint i, chan;
+
+   uint writemask = inst->FullDstRegisters[0].DstRegister.WriteMask;
+   if (writemask == TGSI_WRITEMASK_X ||
+       writemask == TGSI_WRITEMASK_Y ||
+       writemask == TGSI_WRITEMASK_Z ||
+       writemask == TGSI_WRITEMASK_W ||
+       writemask == TGSI_WRITEMASK_NONE) {
+      /* no chance of data dependency */
+      return FALSE;
+   }
+
+   /* loop over src regs */
+   for (i = 0; i < inst->Instruction.NumSrcRegs; i++) {
+      if ((inst->FullSrcRegisters[i].SrcRegister.File ==
+           inst->FullDstRegisters[0].DstRegister.File) &&
+          (inst->FullSrcRegisters[i].SrcRegister.Index ==
+           inst->FullDstRegisters[0].DstRegister.Index)) {
+         /* loop over dest channels */
+         uint channelsWritten = 0x0;
+         FOR_EACH_ENABLED_CHANNEL(*inst, chan) {
+            /* check if we're reading a channel that's been written */
+            uint swizzle = tgsi_util_get_full_src_register_extswizzle(&inst->FullSrcRegisters[i], chan);
+            if (swizzle <= TGSI_SWIZZLE_W &&
+                (channelsWritten & (1 << swizzle))) {
+               return TRUE;
+            }
+
+            channelsWritten |= (1 << chan);
+         }
+      }
+   }
+   return FALSE;
+}
+
 
 /**
  * Initialize machine state by expanding tokens to full instructions,
@@ -280,6 +331,17 @@ tgsi_exec_machine_bind_shader(
          memcpy(instructions + numInstructions,
                 &parse.FullToken.FullInstruction,
                 sizeof(instructions[0]));
+
+#if 0
+         if (tgsi_check_soa_dependencies(&parse.FullToken.FullInstruction)) {
+            debug_printf("SOA dependency in instruction:\n");
+            tgsi_dump_instruction(&parse.FullToken.FullInstruction,
+                                  numInstructions);
+         }
+#else
+         (void) tgsi_check_soa_dependencies;
+#endif
+
          numInstructions++;
          break;