/* * Mesa 3-D graphics library * * Copyright (C) 2009 VMware, Inc. All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included * in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * VMWARE BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ #include "main/glheader.h" #include "main/context.h" #include "main/macros.h" #include "program.h" #include "prog_instruction.h" #include "prog_optimize.h" #include "prog_print.h" #define MAX_LOOP_NESTING 50 /* MAX_PROGRAM_TEMPS is a low number (256), and we want to be able to * register allocate many temporary values into that small number of * temps. So allow large temporary indices coming into the register * allocator. */ #define REG_ALLOCATE_MAX_PROGRAM_TEMPS ((1 << INST_INDEX_BITS) - 1) static GLboolean dbg = GL_FALSE; #define NO_MASK 0xf /** * Returns the mask of channels (bitmask of WRITEMASK_X,Y,Z,W) which * are read from the given src in this instruction, We also provide * one optional masks which may mask other components in the dst * register */ static GLuint get_src_arg_mask(const struct prog_instruction *inst, GLuint arg, GLuint dst_mask) { GLuint read_mask, channel_mask; GLuint comp; assert(arg < _mesa_num_inst_src_regs(inst->Opcode)); /* Form the dst register, find the written channels */ switch (inst->Opcode) { case OPCODE_MOV: case OPCODE_MIN: case OPCODE_MAX: case OPCODE_ABS: case OPCODE_ADD: case OPCODE_MAD: case OPCODE_MUL: case OPCODE_SUB: case OPCODE_CMP: case OPCODE_FLR: case OPCODE_FRC: case OPCODE_LRP: case OPCODE_SGE: case OPCODE_SLT: case OPCODE_SSG: channel_mask = inst->DstReg.WriteMask & dst_mask; break; case OPCODE_RCP: case OPCODE_SIN: case OPCODE_COS: case OPCODE_RSQ: case OPCODE_POW: case OPCODE_EX2: case OPCODE_LOG: channel_mask = WRITEMASK_X; break; case OPCODE_DP2: channel_mask = WRITEMASK_XY; break; case OPCODE_DP3: case OPCODE_XPD: channel_mask = WRITEMASK_XYZ; break; default: channel_mask = WRITEMASK_XYZW; break; } /* Now, given the src swizzle and the written channels, find which * components are actually read */ read_mask = 0x0; for (comp = 0; comp < 4; ++comp) { const GLuint coord = GET_SWZ(inst->SrcReg[arg].Swizzle, comp); if (channel_mask & (1 << comp) && coord <= SWIZZLE_W) read_mask |= 1 << coord; } return read_mask; } /** * For a MOV instruction, compute a write mask when src register also has * a mask */ static GLuint get_dst_mask_for_mov(const struct prog_instruction *mov, GLuint src_mask) { const GLuint mask = mov->DstReg.WriteMask; GLuint comp; GLuint updated_mask = 0x0; assert(mov->Opcode == OPCODE_MOV); for (comp = 0; comp < 4; ++comp) { GLuint src_comp; if ((mask & (1 << comp)) == 0) continue; src_comp = GET_SWZ(mov->SrcReg[0].Swizzle, comp); if ((src_mask & (1 << src_comp)) == 0) continue; updated_mask |= 1 << comp; } return updated_mask; } /** * Ensure that the swizzle is regular. That is, all of the swizzle * terms are SWIZZLE_X,Y,Z,W and not SWIZZLE_ZERO or SWIZZLE_ONE. */ static GLboolean is_swizzle_regular(GLuint swz) { return GET_SWZ(swz,0) <= SWIZZLE_W && GET_SWZ(swz,1) <= SWIZZLE_W && GET_SWZ(swz,2) <= SWIZZLE_W && GET_SWZ(swz,3) <= SWIZZLE_W; } /** * In 'prog' remove instruction[i] if removeFlags[i] == TRUE. * \return number of instructions removed */ static GLuint remove_instructions(struct gl_program *prog, const GLboolean *removeFlags) { GLint i, removeEnd = 0, removeCount = 0; GLuint totalRemoved = 0; /* go backward */ for (i = prog->NumInstructions - 1; i >= 0; i--) { if (removeFlags[i]) { totalRemoved++; if (removeCount == 0) { /* begin a run of instructions to remove */ removeEnd = i; removeCount = 1; } else { /* extend the run of instructions to remove */ removeCount++; } } else { /* don't remove this instruction, but check if the preceeding * instructions are to be removed. */ if (removeCount > 0) { GLint removeStart = removeEnd - removeCount + 1; _mesa_delete_instructions(prog, removeStart, removeCount); removeStart = removeCount = 0; /* reset removal info */ } } } /* Finish removing if the first instruction was to be removed. */ if (removeCount > 0) { GLint removeStart = removeEnd - removeCount + 1; _mesa_delete_instructions(prog, removeStart, removeCount); } return totalRemoved; } /** * Remap register indexes according to map. * \param prog the program to search/replace * \param file the type of register file to search/replace * \param map maps old register indexes to new indexes */ static void replace_regs(struct gl_program *prog, gl_register_file file, const GLint map[]) { GLuint i; for (i = 0; i < prog->NumInstructions; i++) { struct prog_instruction *inst = prog->Instructions + i; const GLuint numSrc = _mesa_num_inst_src_regs(inst->Opcode); GLuint j; for (j = 0; j < numSrc; j++) { if (inst->SrcReg[j].File == file) { GLuint index = inst->SrcReg[j].Index; assert(map[index] >= 0); inst->SrcReg[j].Index = map[index]; } } if (inst->DstReg.File == file) { const GLuint index = inst->DstReg.Index; assert(map[index] >= 0); inst->DstReg.Index = map[index]; } } } /** * Remove dead instructions from the given program. * This is very primitive for now. Basically look for temp registers * that are written to but never read. Remove any instructions that * write to such registers. Be careful with condition code setters. */ static GLboolean _mesa_remove_dead_code_global(struct gl_program *prog) { GLboolean tempRead[REG_ALLOCATE_MAX_PROGRAM_TEMPS][4]; GLboolean *removeInst; /* per-instruction removal flag */ GLuint i, rem = 0, comp; memset(tempRead, 0, sizeof(tempRead)); if (dbg) { printf("Optimize: Begin dead code removal\n"); /*_mesa_print_program(prog);*/ } removeInst = calloc(prog->NumInstructions, sizeof(GLboolean)); /* Determine which temps are read and written */ for (i = 0; i < prog->NumInstructions; i++) { const struct prog_instruction *inst = prog->Instructions + i; const GLuint numSrc = _mesa_num_inst_src_regs(inst->Opcode); GLuint j; /* check src regs */ for (j = 0; j < numSrc; j++) { if (inst->SrcReg[j].File == PROGRAM_TEMPORARY) { const GLuint index = inst->SrcReg[j].Index; GLuint read_mask; assert(index < REG_ALLOCATE_MAX_PROGRAM_TEMPS); read_mask = get_src_arg_mask(inst, j, NO_MASK); if (inst->SrcReg[j].RelAddr) { if (dbg) printf("abort remove dead code (indirect temp)\n"); goto done; } for (comp = 0; comp < 4; comp++) { const GLuint swz = GET_SWZ(inst->SrcReg[j].Swizzle, comp); if (swz <= SWIZZLE_W) { if ((read_mask & (1 << swz)) == 0) continue; tempRead[index][swz] = GL_TRUE; } } } } /* check dst reg */ if (inst->DstReg.File == PROGRAM_TEMPORARY) { assert(inst->DstReg.Index < REG_ALLOCATE_MAX_PROGRAM_TEMPS); if (inst->DstReg.RelAddr) { if (dbg) printf("abort remove dead code (indirect temp)\n"); goto done; } } } /* find instructions that write to dead registers, flag for removal */ for (i = 0; i < prog->NumInstructions; i++) { struct prog_instruction *inst = prog->Instructions + i; const GLuint numDst = _mesa_num_inst_dst_regs(inst->Opcode); if (numDst != 0 && inst->DstReg.File == PROGRAM_TEMPORARY) { GLint chan, index = inst->DstReg.Index; for (chan = 0; chan < 4; chan++) { if (!tempRead[index][chan] && inst->DstReg.WriteMask & (1 << chan)) { if (dbg) { printf("Remove writemask on %u.%c\n", i, chan == 3 ? 'w' : 'x' + chan); } inst->DstReg.WriteMask &= ~(1 << chan); rem++; } } if (inst->DstReg.WriteMask == 0) { /* If we cleared all writes, the instruction can be removed. */ if (dbg) printf("Remove instruction %u: \n", i); removeInst[i] = GL_TRUE; } } } /* now remove the instructions which aren't needed */ rem = remove_instructions(prog, removeInst); if (dbg) { printf("Optimize: End dead code removal.\n"); printf(" %u channel writes removed\n", rem); printf(" %u instructions removed\n", rem); /*_mesa_print_program(prog);*/ } done: free(removeInst); return rem != 0; } enum inst_use { READ, WRITE, FLOW, END }; /** * Scan forward in program from 'start' for the next occurances of TEMP[index]. * We look if an instruction reads the component given by the masks and if they * are overwritten. * Return READ, WRITE, FLOW or END to indicate the next usage or an indicator * that we can't look further. */ static enum inst_use find_next_use(const struct gl_program *prog, GLuint start, GLuint index, GLuint mask) { GLuint i; for (i = start; i < prog->NumInstructions; i++) { const struct prog_instruction *inst = prog->Instructions + i; switch (inst->Opcode) { case OPCODE_BGNLOOP: case OPCODE_BGNSUB: case OPCODE_CAL: case OPCODE_CONT: case OPCODE_IF: case OPCODE_ELSE: case OPCODE_ENDIF: case OPCODE_ENDLOOP: case OPCODE_ENDSUB: case OPCODE_RET: return FLOW; case OPCODE_END: return END; default: { const GLuint numSrc = _mesa_num_inst_src_regs(inst->Opcode); GLuint j; for (j = 0; j < numSrc; j++) { if (inst->SrcReg[j].RelAddr || (inst->SrcReg[j].File == PROGRAM_TEMPORARY && inst->SrcReg[j].Index == (GLint)index && (get_src_arg_mask(inst,j,NO_MASK) & mask))) return READ; } if (_mesa_num_inst_dst_regs(inst->Opcode) == 1 && inst->DstReg.File == PROGRAM_TEMPORARY && inst->DstReg.Index == index) { mask &= ~inst->DstReg.WriteMask; if (mask == 0) return WRITE; } } } } return END; } /** * Is the given instruction opcode a flow-control opcode? * XXX maybe move this into prog_instruction.[ch] */ static GLboolean _mesa_is_flow_control_opcode(enum prog_opcode opcode) { switch (opcode) { case OPCODE_BGNLOOP: case OPCODE_BGNSUB: case OPCODE_CAL: case OPCODE_CONT: case OPCODE_IF: case OPCODE_ELSE: case OPCODE_END: case OPCODE_ENDIF: case OPCODE_ENDLOOP: case OPCODE_ENDSUB: case OPCODE_RET: return GL_TRUE; default: return GL_FALSE; } } /** * Test if the given instruction is a simple MOV (no conditional updating, * not relative addressing, no negation/abs, etc). */ static GLboolean can_downward_mov_be_modifed(const struct prog_instruction *mov) { return mov->Opcode == OPCODE_MOV && mov->SrcReg[0].RelAddr == 0 && mov->SrcReg[0].Negate == 0 && mov->DstReg.RelAddr == 0; } static GLboolean can_upward_mov_be_modifed(const struct prog_instruction *mov) { return can_downward_mov_be_modifed(mov) && mov->DstReg.File == PROGRAM_TEMPORARY && !mov->Saturate; } /** * Try to remove use of extraneous MOV instructions, to free them up for dead * code removal. */ static void _mesa_remove_extra_move_use(struct gl_program *prog) { GLuint i, j; if (dbg) { printf("Optimize: Begin remove extra move use\n"); _mesa_print_program(prog); } /* * Look for sequences such as this: * MOV tmpX, arg0; * ... * FOO tmpY, tmpX, arg1; * and convert into: * MOV tmpX, arg0; * ... * FOO tmpY, arg0, arg1; */ for (i = 0; i + 1 < prog->NumInstructions; i++) { const struct prog_instruction *mov = prog->Instructions + i; GLuint dst_mask, src_mask; if (can_upward_mov_be_modifed(mov) == GL_FALSE) continue; /* Scanning the code, we maintain the components which are still active in * these two masks */ dst_mask = mov->DstReg.WriteMask; src_mask = get_src_arg_mask(mov, 0, NO_MASK); /* Walk through remaining instructions until the or src reg gets * rewritten or we get into some flow-control, eliminating the use of * this MOV. */ for (j = i + 1; j < prog->NumInstructions; j++) { struct prog_instruction *inst2 = prog->Instructions + j; GLuint arg; if (_mesa_is_flow_control_opcode(inst2->Opcode)) break; /* First rewrite this instruction's args if appropriate. */ for (arg = 0; arg < _mesa_num_inst_src_regs(inst2->Opcode); arg++) { GLuint comp, read_mask; if (inst2->SrcReg[arg].File != mov->DstReg.File || inst2->SrcReg[arg].Index != mov->DstReg.Index || inst2->SrcReg[arg].RelAddr) continue; read_mask = get_src_arg_mask(inst2, arg, NO_MASK); /* Adjust the swizzles of inst2 to point at MOV's source if ALL the * components read still come from the mov instructions */ if (is_swizzle_regular(inst2->SrcReg[arg].Swizzle) && (read_mask & dst_mask) == read_mask) { for (comp = 0; comp < 4; comp++) { const GLuint inst2_swz = GET_SWZ(inst2->SrcReg[arg].Swizzle, comp); const GLuint s = GET_SWZ(mov->SrcReg[0].Swizzle, inst2_swz); inst2->SrcReg[arg].Swizzle &= ~(7 << (3 * comp)); inst2->SrcReg[arg].Swizzle |= s << (3 * comp); inst2->SrcReg[arg].Negate ^= (((mov->SrcReg[0].Negate >> inst2_swz) & 0x1) << comp); } inst2->SrcReg[arg].File = mov->SrcReg[0].File; inst2->SrcReg[arg].Index = mov->SrcReg[0].Index; } } /* The source of MOV is written. This potentially deactivates some * components from the src and dst of the MOV instruction */ if (inst2->DstReg.File == mov->DstReg.File && (inst2->DstReg.RelAddr || inst2->DstReg.Index == mov->DstReg.Index)) { dst_mask &= ~inst2->DstReg.WriteMask; src_mask = get_src_arg_mask(mov, 0, dst_mask); } /* Idem when the destination of mov is written */ if (inst2->DstReg.File == mov->SrcReg[0].File && (inst2->DstReg.RelAddr || inst2->DstReg.Index == mov->SrcReg[0].Index)) { src_mask &= ~inst2->DstReg.WriteMask; dst_mask &= get_dst_mask_for_mov(mov, src_mask); } if (dst_mask == 0) break; } } if (dbg) { printf("Optimize: End remove extra move use.\n"); /*_mesa_print_program(prog);*/ } } /** * Complements dead_code_global. Try to remove code in block of code by * carefully monitoring the swizzles. Both functions should be merged into one * with a proper control flow graph */ static GLboolean _mesa_remove_dead_code_local(struct gl_program *prog) { GLboolean *removeInst; GLuint i, arg, rem = 0; removeInst = calloc(prog->NumInstructions, sizeof(GLboolean)); for (i = 0; i < prog->NumInstructions; i++) { const struct prog_instruction *inst = prog->Instructions + i; const GLuint index = inst->DstReg.Index; const GLuint mask = inst->DstReg.WriteMask; enum inst_use use; /* We must deactivate the pass as soon as some indirection is used */ if (inst->DstReg.RelAddr) goto done; for (arg = 0; arg < _mesa_num_inst_src_regs(inst->Opcode); arg++) if (inst->SrcReg[arg].RelAddr) goto done; if (_mesa_is_flow_control_opcode(inst->Opcode) || _mesa_num_inst_dst_regs(inst->Opcode) == 0 || inst->DstReg.File != PROGRAM_TEMPORARY || inst->DstReg.RelAddr) continue; use = find_next_use(prog, i+1, index, mask); if (use == WRITE || use == END) removeInst[i] = GL_TRUE; } rem = remove_instructions(prog, removeInst); done: free(removeInst); return rem != 0; } /** * Try to inject the destination of mov as the destination of inst and recompute * the swizzles operators for the sources of inst if required. Return GL_TRUE * of the substitution was possible, GL_FALSE otherwise */ static GLboolean _mesa_merge_mov_into_inst(struct prog_instruction *inst, const struct prog_instruction *mov) { /* Indirection table which associates destination and source components for * the mov instruction */ const GLuint mask = get_src_arg_mask(mov, 0, NO_MASK); /* Some components are not written by inst. We cannot remove the mov */ if (mask != (inst->DstReg.WriteMask & mask)) return GL_FALSE; inst->Saturate |= mov->Saturate; /* Depending on the instruction, we may need to recompute the swizzles. * Also, some other instructions (like TEX) are not linear. We will only * consider completely active sources and destinations */ switch (inst->Opcode) { /* Carstesian instructions: we compute the swizzle */ case OPCODE_MOV: case OPCODE_MIN: case OPCODE_MAX: case OPCODE_ABS: case OPCODE_ADD: case OPCODE_MAD: case OPCODE_MUL: case OPCODE_SUB: { GLuint dst_to_src_comp[4] = {0,0,0,0}; GLuint dst_comp, arg; for (dst_comp = 0; dst_comp < 4; ++dst_comp) { if (mov->DstReg.WriteMask & (1 << dst_comp)) { const GLuint src_comp = GET_SWZ(mov->SrcReg[0].Swizzle, dst_comp); assert(src_comp < 4); dst_to_src_comp[dst_comp] = src_comp; } } /* Patch each source of the instruction */ for (arg = 0; arg < _mesa_num_inst_src_regs(inst->Opcode); arg++) { const GLuint arg_swz = inst->SrcReg[arg].Swizzle; inst->SrcReg[arg].Swizzle = 0; /* Reset each active component of the swizzle */ for (dst_comp = 0; dst_comp < 4; ++dst_comp) { GLuint src_comp, arg_comp; if ((mov->DstReg.WriteMask & (1 << dst_comp)) == 0) continue; src_comp = dst_to_src_comp[dst_comp]; assert(src_comp < 4); arg_comp = GET_SWZ(arg_swz, src_comp); assert(arg_comp < 4); inst->SrcReg[arg].Swizzle |= arg_comp << (3*dst_comp); } } inst->DstReg = mov->DstReg; return GL_TRUE; } /* Dot products and scalar instructions: we only change the destination */ case OPCODE_RCP: case OPCODE_SIN: case OPCODE_COS: case OPCODE_RSQ: case OPCODE_POW: case OPCODE_EX2: case OPCODE_LOG: case OPCODE_DP2: case OPCODE_DP3: case OPCODE_DP4: inst->DstReg = mov->DstReg; return GL_TRUE; /* All other instructions require fully active components with no swizzle */ default: if (mov->SrcReg[0].Swizzle != SWIZZLE_XYZW || inst->DstReg.WriteMask != WRITEMASK_XYZW) return GL_FALSE; inst->DstReg = mov->DstReg; return GL_TRUE; } } /** * Try to remove extraneous MOV instructions from the given program. */ static GLboolean _mesa_remove_extra_moves(struct gl_program *prog) { GLboolean *removeInst; /* per-instruction removal flag */ GLuint i, rem = 0, nesting = 0; if (dbg) { printf("Optimize: Begin remove extra moves\n"); _mesa_print_program(prog); } removeInst = calloc(prog->NumInstructions, sizeof(GLboolean)); /* * Look for sequences such as this: * FOO tmpX, arg0, arg1; * MOV tmpY, tmpX; * and convert into: * FOO tmpY, arg0, arg1; */ for (i = 0; i < prog->NumInstructions; i++) { const struct prog_instruction *mov = prog->Instructions + i; switch (mov->Opcode) { case OPCODE_BGNLOOP: case OPCODE_BGNSUB: case OPCODE_IF: nesting++; break; case OPCODE_ENDLOOP: case OPCODE_ENDSUB: case OPCODE_ENDIF: nesting--; break; case OPCODE_MOV: if (i > 0 && can_downward_mov_be_modifed(mov) && mov->SrcReg[0].File == PROGRAM_TEMPORARY && nesting == 0) { /* see if this MOV can be removed */ const GLuint id = mov->SrcReg[0].Index; struct prog_instruction *prevInst; GLuint prevI; /* get pointer to previous instruction */ prevI = i - 1; while (prevI > 0 && removeInst[prevI]) prevI--; prevInst = prog->Instructions + prevI; if (prevInst->DstReg.File == PROGRAM_TEMPORARY && prevInst->DstReg.Index == id && prevInst->DstReg.RelAddr == 0) { const GLuint dst_mask = prevInst->DstReg.WriteMask; enum inst_use next_use = find_next_use(prog, i+1, id, dst_mask); if (next_use == WRITE || next_use == END) { /* OK, we can safely remove this MOV instruction. * Transform: * prevI: FOO tempIndex, x, y; * i: MOV z, tempIndex; * Into: * prevI: FOO z, x, y; */ if (_mesa_merge_mov_into_inst(prevInst, mov)) { removeInst[i] = GL_TRUE; if (dbg) { printf("Remove MOV at %u\n", i); printf("new prev inst %u: ", prevI); _mesa_print_instruction(prevInst); } } } } } break; default: ; /* nothing */ } } /* now remove the instructions which aren't needed */ rem = remove_instructions(prog, removeInst); free(removeInst); if (dbg) { printf("Optimize: End remove extra moves. %u instructions removed\n", rem); /*_mesa_print_program(prog);*/ } return rem != 0; } /** A live register interval */ struct interval { GLuint Reg; /** The temporary register index */ GLuint Start, End; /** Start/end instruction numbers */ }; /** A list of register intervals */ struct interval_list { GLuint Num; struct interval Intervals[REG_ALLOCATE_MAX_PROGRAM_TEMPS]; }; static void append_interval(struct interval_list *list, const struct interval *inv) { list->Intervals[list->Num++] = *inv; } /** Insert interval inv into list, sorted by interval end */ static void insert_interval_by_end(struct interval_list *list, const struct interval *inv) { /* XXX we could do a binary search insertion here since list is sorted */ GLint i = list->Num - 1; while (i >= 0 && list->Intervals[i].End > inv->End) { list->Intervals[i + 1] = list->Intervals[i]; i--; } list->Intervals[i + 1] = *inv; list->Num++; #ifdef DEBUG { GLuint i; for (i = 0; i + 1 < list->Num; i++) { assert(list->Intervals[i].End <= list->Intervals[i + 1].End); } } #endif } /** Remove the given interval from the interval list */ static void remove_interval(struct interval_list *list, const struct interval *inv) { /* XXX we could binary search since list is sorted */ GLuint k; for (k = 0; k < list->Num; k++) { if (list->Intervals[k].Reg == inv->Reg) { /* found, remove it */ assert(list->Intervals[k].Start == inv->Start); assert(list->Intervals[k].End == inv->End); while (k < list->Num - 1) { list->Intervals[k] = list->Intervals[k + 1]; k++; } list->Num--; return; } } } /** called by qsort() */ static int compare_start(const void *a, const void *b) { const struct interval *ia = (const struct interval *) a; const struct interval *ib = (const struct interval *) b; if (ia->Start < ib->Start) return -1; else if (ia->Start > ib->Start) return +1; else return 0; } /** sort the interval list according to interval starts */ static void sort_interval_list_by_start(struct interval_list *list) { qsort(list->Intervals, list->Num, sizeof(struct interval), compare_start); #ifdef DEBUG { GLuint i; for (i = 0; i + 1 < list->Num; i++) { assert(list->Intervals[i].Start <= list->Intervals[i + 1].Start); } } #endif } struct loop_info { GLuint Start, End; /**< Start, end instructions of loop */ }; /** * Update the intermediate interval info for register 'index' and * instruction 'ic'. */ static void update_interval(GLint intBegin[], GLint intEnd[], struct loop_info *loopStack, GLuint loopStackDepth, GLuint index, GLuint ic) { unsigned i; GLuint begin = ic; GLuint end = ic; /* If the register is used in a loop, extend its lifetime through the end * of the outermost loop that doesn't contain its definition. */ for (i = 0; i < loopStackDepth; i++) { if (intBegin[index] < loopStack[i].Start) { end = loopStack[i].End; break; } } /* Variables that are live at the end of a loop will also be live at the * beginning, so an instruction inside of a loop should have its live * interval begin at the start of the outermost loop. */ if (loopStackDepth > 0 && ic > loopStack[0].Start && ic < loopStack[0].End) { begin = loopStack[0].Start; } assert(index < REG_ALLOCATE_MAX_PROGRAM_TEMPS); if (intBegin[index] == -1) { assert(intEnd[index] == -1); intBegin[index] = begin; intEnd[index] = end; } else { intEnd[index] = end; } } /** * Find first/last instruction that references each temporary register. */ GLboolean _mesa_find_temp_intervals(const struct prog_instruction *instructions, GLuint numInstructions, GLint intBegin[REG_ALLOCATE_MAX_PROGRAM_TEMPS], GLint intEnd[REG_ALLOCATE_MAX_PROGRAM_TEMPS]) { struct loop_info loopStack[MAX_LOOP_NESTING]; GLuint loopStackDepth = 0; GLuint i; for (i = 0; i < REG_ALLOCATE_MAX_PROGRAM_TEMPS; i++){ intBegin[i] = intEnd[i] = -1; } /* Scan instructions looking for temporary registers */ for (i = 0; i < numInstructions; i++) { const struct prog_instruction *inst = instructions + i; if (inst->Opcode == OPCODE_BGNLOOP) { loopStack[loopStackDepth].Start = i; loopStack[loopStackDepth].End = inst->BranchTarget; loopStackDepth++; } else if (inst->Opcode == OPCODE_ENDLOOP) { loopStackDepth--; } else if (inst->Opcode == OPCODE_CAL) { return GL_FALSE; } else { const GLuint numSrc = 3;/*_mesa_num_inst_src_regs(inst->Opcode);*/ GLuint j; for (j = 0; j < numSrc; j++) { if (inst->SrcReg[j].File == PROGRAM_TEMPORARY) { const GLuint index = inst->SrcReg[j].Index; if (inst->SrcReg[j].RelAddr) return GL_FALSE; update_interval(intBegin, intEnd, loopStack, loopStackDepth, index, i); } } if (inst->DstReg.File == PROGRAM_TEMPORARY) { const GLuint index = inst->DstReg.Index; if (inst->DstReg.RelAddr) return GL_FALSE; update_interval(intBegin, intEnd, loopStack, loopStackDepth, index, i); } } } return GL_TRUE; } /** * Find the live intervals for each temporary register in the program. * For register R, the interval [A,B] indicates that R is referenced * from instruction A through instruction B. * Special consideration is needed for loops and subroutines. * \return GL_TRUE if success, GL_FALSE if we cannot proceed for some reason */ static GLboolean find_live_intervals(struct gl_program *prog, struct interval_list *liveIntervals) { GLint intBegin[REG_ALLOCATE_MAX_PROGRAM_TEMPS]; GLint intEnd[REG_ALLOCATE_MAX_PROGRAM_TEMPS]; GLuint i; /* * Note: we'll return GL_FALSE below if we find relative indexing * into the TEMP register file. We can't handle that yet. * We also give up on subroutines for now. */ if (dbg) { printf("Optimize: Begin find intervals\n"); } /* build intermediate arrays */ if (!_mesa_find_temp_intervals(prog->Instructions, prog->NumInstructions, intBegin, intEnd)) return GL_FALSE; /* Build live intervals list from intermediate arrays */ liveIntervals->Num = 0; for (i = 0; i < REG_ALLOCATE_MAX_PROGRAM_TEMPS; i++) { if (intBegin[i] >= 0) { struct interval inv; inv.Reg = i; inv.Start = intBegin[i]; inv.End = intEnd[i]; append_interval(liveIntervals, &inv); } } /* Sort the list according to interval starts */ sort_interval_list_by_start(liveIntervals); if (dbg) { /* print interval info */ for (i = 0; i < liveIntervals->Num; i++) { const struct interval *inv = liveIntervals->Intervals + i; printf("Reg[%d] live [%d, %d]:", inv->Reg, inv->Start, inv->End); if (1) { GLuint j; for (j = 0; j < inv->Start; j++) printf(" "); for (j = inv->Start; j <= inv->End; j++) printf("x"); } printf("\n"); } } return GL_TRUE; } /** Scan the array of used register flags to find free entry */ static GLint alloc_register(GLboolean usedRegs[REG_ALLOCATE_MAX_PROGRAM_TEMPS]) { GLuint k; for (k = 0; k < REG_ALLOCATE_MAX_PROGRAM_TEMPS; k++) { if (!usedRegs[k]) { usedRegs[k] = GL_TRUE; return k; } } return -1; } /** * This function implements "Linear Scan Register Allocation" to reduce * the number of temporary registers used by the program. * * We compute the "live interval" for all temporary registers then * examine the overlap of the intervals to allocate new registers. * Basically, if two intervals do not overlap, they can use the same register. */ static void _mesa_reallocate_registers(struct gl_program *prog) { struct interval_list liveIntervals; GLint registerMap[REG_ALLOCATE_MAX_PROGRAM_TEMPS]; GLboolean usedRegs[REG_ALLOCATE_MAX_PROGRAM_TEMPS]; GLuint i; GLint maxTemp = -1; if (dbg) { printf("Optimize: Begin live-interval register reallocation\n"); _mesa_print_program(prog); } for (i = 0; i < REG_ALLOCATE_MAX_PROGRAM_TEMPS; i++){ registerMap[i] = -1; usedRegs[i] = GL_FALSE; } if (!find_live_intervals(prog, &liveIntervals)) { if (dbg) printf("Aborting register reallocation\n"); return; } { struct interval_list activeIntervals; activeIntervals.Num = 0; /* loop over live intervals, allocating a new register for each */ for (i = 0; i < liveIntervals.Num; i++) { const struct interval *live = liveIntervals.Intervals + i; if (dbg) printf("Consider register %u\n", live->Reg); /* Expire old intervals. Intervals which have ended with respect * to the live interval can have their remapped registers freed. */ { GLint j; for (j = 0; j < (GLint) activeIntervals.Num; j++) { const struct interval *inv = activeIntervals.Intervals + j; if (inv->End >= live->Start) { /* Stop now. Since the activeInterval list is sorted * we know we don't have to go further. */ break; } else { /* Interval 'inv' has expired */ const GLint regNew = registerMap[inv->Reg]; assert(regNew >= 0); if (dbg) printf(" expire interval for reg %u\n", inv->Reg); /* remove interval j from active list */ remove_interval(&activeIntervals, inv); j--; /* counter-act j++ in for-loop above */ /* return register regNew to the free pool */ if (dbg) printf(" free reg %d\n", regNew); assert(usedRegs[regNew] == GL_TRUE); usedRegs[regNew] = GL_FALSE; } } } /* find a free register for this live interval */ { const GLint k = alloc_register(usedRegs); if (k < 0) { /* out of registers, give up */ return; } registerMap[live->Reg] = k; maxTemp = MAX2(maxTemp, k); if (dbg) printf(" remap register %u -> %d\n", live->Reg, k); } /* Insert this live interval into the active list which is sorted * by increasing end points. */ insert_interval_by_end(&activeIntervals, live); } } if (maxTemp + 1 < (GLint) liveIntervals.Num) { /* OK, we've reduced the number of registers needed. * Scan the program and replace all the old temporary register * indexes with the new indexes. */ replace_regs(prog, PROGRAM_TEMPORARY, registerMap); prog->NumTemporaries = maxTemp + 1; } if (dbg) { printf("Optimize: End live-interval register reallocation\n"); printf("Num temp regs before: %u after: %u\n", liveIntervals.Num, maxTemp + 1); _mesa_print_program(prog); } } #if 0 static void print_it(struct gl_context *ctx, struct gl_program *program, const char *txt) { fprintf(stderr, "%s (%u inst):\n", txt, program->NumInstructions); _mesa_print_program(program); _mesa_print_program_parameters(ctx, program); fprintf(stderr, "\n\n"); } #endif /** * This pass replaces CMP T0, T1 T2 T0 with MOV T0, T2 when the CMP * instruction is the first instruction to write to register T0. The are * several lowering passes done in GLSL IR (e.g. branches and * relative addressing) that create a large number of conditional assignments * that ir_to_mesa converts to CMP instructions like the one mentioned above. * * Here is why this conversion is safe: * CMP T0, T1 T2 T0 can be expanded to: * if (T1 < 0.0) * MOV T0, T2; * else * MOV T0, T0; * * If (T1 < 0.0) evaluates to true then our replacement MOV T0, T2 is the same * as the original program. If (T1 < 0.0) evaluates to false, executing * MOV T0, T0 will store a garbage value in T0 since T0 is uninitialized. * Therefore, it doesn't matter that we are replacing MOV T0, T0 with MOV T0, T2 * because any instruction that was going to read from T0 after this was going * to read a garbage value anyway. */ static void _mesa_simplify_cmp(struct gl_program * program) { GLuint tempWrites[REG_ALLOCATE_MAX_PROGRAM_TEMPS]; GLuint outputWrites[MAX_PROGRAM_OUTPUTS]; GLuint i; if (dbg) { printf("Optimize: Begin reads without writes\n"); _mesa_print_program(program); } for (i = 0; i < REG_ALLOCATE_MAX_PROGRAM_TEMPS; i++) { tempWrites[i] = 0; } for (i = 0; i < MAX_PROGRAM_OUTPUTS; i++) { outputWrites[i] = 0; } for (i = 0; i < program->NumInstructions; i++) { struct prog_instruction *inst = program->Instructions + i; GLuint prevWriteMask; /* Give up if we encounter relative addressing or flow control. */ if (_mesa_is_flow_control_opcode(inst->Opcode) || inst->DstReg.RelAddr) { return; } if (inst->DstReg.File == PROGRAM_OUTPUT) { assert(inst->DstReg.Index < MAX_PROGRAM_OUTPUTS); prevWriteMask = outputWrites[inst->DstReg.Index]; outputWrites[inst->DstReg.Index] |= inst->DstReg.WriteMask; } else if (inst->DstReg.File == PROGRAM_TEMPORARY) { assert(inst->DstReg.Index < REG_ALLOCATE_MAX_PROGRAM_TEMPS); prevWriteMask = tempWrites[inst->DstReg.Index]; tempWrites[inst->DstReg.Index] |= inst->DstReg.WriteMask; } else { /* No other register type can be a destination register. */ continue; } /* For a CMP to be considered a conditional write, the destination * register and source register two must be the same. */ if (inst->Opcode == OPCODE_CMP && !(inst->DstReg.WriteMask & prevWriteMask) && inst->SrcReg[2].File == inst->DstReg.File && inst->SrcReg[2].Index == inst->DstReg.Index && inst->DstReg.WriteMask == get_src_arg_mask(inst, 2, NO_MASK)) { inst->Opcode = OPCODE_MOV; inst->SrcReg[0] = inst->SrcReg[1]; /* Unused operands are expected to have the file set to * PROGRAM_UNDEFINED. This is how _mesa_init_instructions initializes * all of the sources. */ inst->SrcReg[1].File = PROGRAM_UNDEFINED; inst->SrcReg[1].Swizzle = SWIZZLE_NOOP; inst->SrcReg[2].File = PROGRAM_UNDEFINED; inst->SrcReg[2].Swizzle = SWIZZLE_NOOP; } } if (dbg) { printf("Optimize: End reads without writes\n"); _mesa_print_program(program); } } /** * Apply optimizations to the given program to eliminate unnecessary * instructions, temp regs, etc. */ void _mesa_optimize_program(struct gl_context *ctx, struct gl_program *program) { GLboolean any_change; _mesa_simplify_cmp(program); /* Stop when no modifications were output */ do { any_change = GL_FALSE; _mesa_remove_extra_move_use(program); if (_mesa_remove_dead_code_global(program)) any_change = GL_TRUE; if (_mesa_remove_extra_moves(program)) any_change = GL_TRUE; if (_mesa_remove_dead_code_local(program)) any_change = GL_TRUE; any_change = _mesa_constant_fold(program) || any_change; _mesa_reallocate_registers(program); } while (any_change); }