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diff --git a/src/cmd/5l/noop.c b/src/cmd/5l/noop.c
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+// Inferno utils/5l/noop.c
+// http://code.google.com/p/inferno-os/source/browse/utils/5l/noop.c
+//
+// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
+// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
+// Portions Copyright © 1997-1999 Vita Nuova Limited
+// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
+// Portions Copyright © 2004,2006 Bruce Ellis
+// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
+// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
+// Portions Copyright © 2009 The Go Authors. 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 THE
+// AUTHORS OR COPYRIGHT HOLDERS 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.
+
+// Code transformations.
+
+#include "l.h"
+#include "../ld/lib.h"
+
+// see ../../runtime/proc.c:/StackGuard
+enum
+{
+ StackBig = 4096,
+ StackSmall = 128,
+};
+
+static Sym* sym_div;
+static Sym* sym_divu;
+static Sym* sym_mod;
+static Sym* sym_modu;
+
+void
+noops(void)
+{
+ Prog *p, *q, *q1;
+ int o;
+ Prog *pmorestack;
+ Sym *symmorestack;
+
+ /*
+ * find leaf subroutines
+ * strip NOPs
+ * expand RET
+ * expand BECOME pseudo
+ */
+
+ if(debug['v'])
+ Bprint(&bso, "%5.2f noops\n", cputime());
+ Bflush(&bso);
+
+ symmorestack = lookup("runtime.morestack", 0);
+ if(symmorestack->type != STEXT) {
+ diag("runtime·morestack not defined");
+ errorexit();
+ }
+ pmorestack = symmorestack->text;
+ pmorestack->reg |= NOSPLIT;
+
+ q = P;
+ for(cursym = textp; cursym != nil; cursym = cursym->next) {
+ for(p = cursym->text; p != P; p = p->link) {
+ switch(p->as) {
+ case ATEXT:
+ p->mark |= LEAF;
+ break;
+
+ case ARET:
+ break;
+
+ case ADIV:
+ case ADIVU:
+ case AMOD:
+ case AMODU:
+ q = p;
+ if(prog_div == P)
+ initdiv();
+ cursym->text->mark &= ~LEAF;
+ continue;
+
+ case ANOP:
+ q1 = p->link;
+ q->link = q1; /* q is non-nop */
+ if(q1 != P)
+ q1->mark |= p->mark;
+ continue;
+
+ case ABL:
+ case ABX:
+ cursym->text->mark &= ~LEAF;
+
+ case ABCASE:
+ case AB:
+
+ case ABEQ:
+ case ABNE:
+ case ABCS:
+ case ABHS:
+ case ABCC:
+ case ABLO:
+ case ABMI:
+ case ABPL:
+ case ABVS:
+ case ABVC:
+ case ABHI:
+ case ABLS:
+ case ABGE:
+ case ABLT:
+ case ABGT:
+ case ABLE:
+ q1 = p->cond;
+ if(q1 != P) {
+ while(q1->as == ANOP) {
+ q1 = q1->link;
+ p->cond = q1;
+ }
+ }
+ break;
+ }
+ q = p;
+ }
+ }
+
+ for(cursym = textp; cursym != nil; cursym = cursym->next) {
+ for(p = cursym->text; p != P; p = p->link) {
+ o = p->as;
+ switch(o) {
+ case ATEXT:
+ autosize = p->to.offset + 4;
+ if(autosize <= 4)
+ if(cursym->text->mark & LEAF) {
+ p->to.offset = -4;
+ autosize = 0;
+ }
+
+ if(!autosize && !(cursym->text->mark & LEAF)) {
+ if(debug['v'])
+ Bprint(&bso, "save suppressed in: %s\n",
+ cursym->name);
+ Bflush(&bso);
+ cursym->text->mark |= LEAF;
+ }
+ if(cursym->text->mark & LEAF) {
+ cursym->leaf = 1;
+ if(!autosize)
+ break;
+ }
+
+ if(p->reg & NOSPLIT) {
+ q1 = prg();
+ q1->as = AMOVW;
+ q1->scond |= C_WBIT;
+ q1->line = p->line;
+ q1->from.type = D_REG;
+ q1->from.reg = REGLINK;
+ q1->to.type = D_OREG;
+ q1->to.offset = -autosize;
+ q1->to.reg = REGSP;
+ q1->spadj = autosize;
+ q1->link = p->link;
+ p->link = q1;
+ } else if (autosize < StackBig) {
+ // split stack check for small functions
+ // MOVW g_stackguard(g), R1
+ // CMP R1, $-autosize(SP)
+ // MOVW.LO $autosize, R1
+ // MOVW.LO $args, R2
+ // MOVW.LO R14, R3
+ // BL.LO runtime.morestack(SB) // modifies LR
+ // MOVW.W R14,$-autosize(SP)
+
+ // TODO(kaib): add more trampolines
+ // TODO(kaib): put stackguard in register
+ // TODO(kaib): add support for -K and underflow detection
+
+ // MOVW g_stackguard(g), R1
+ p = appendp(p);
+ p->as = AMOVW;
+ p->from.type = D_OREG;
+ p->from.reg = REGG;
+ p->to.type = D_REG;
+ p->to.reg = 1;
+
+ if(autosize < StackSmall) {
+ // CMP R1, SP
+ p = appendp(p);
+ p->as = ACMP;
+ p->from.type = D_REG;
+ p->from.reg = 1;
+ p->reg = REGSP;
+ } else {
+ // MOVW $-autosize(SP), R2
+ // CMP R1, R2
+ p = appendp(p);
+ p->as = AMOVW;
+ p->from.type = D_CONST;
+ p->from.reg = REGSP;
+ p->from.offset = -autosize;
+ p->to.type = D_REG;
+ p->to.reg = 2;
+
+ p = appendp(p);
+ p->as = ACMP;
+ p->from.type = D_REG;
+ p->from.reg = 1;
+ p->reg = 2;
+ }
+
+ // MOVW.LO $autosize, R1
+ p = appendp(p);
+ p->as = AMOVW;
+ p->scond = C_SCOND_LO;
+ p->from.type = D_CONST;
+ /* 160 comes from 3 calls (3*8) 4 safes (4*8) and 104 guard */
+ p->from.offset = autosize+160;
+ p->to.type = D_REG;
+ p->to.reg = 1;
+
+ // MOVW.LO $args, R2
+ p = appendp(p);
+ p->as = AMOVW;
+ p->scond = C_SCOND_LO;
+ p->from.type = D_CONST;
+ p->from.offset = (cursym->text->to.offset2 + 3) & ~3;
+ p->to.type = D_REG;
+ p->to.reg = 2;
+
+ // MOVW.LO R14, R3
+ p = appendp(p);
+ p->as = AMOVW;
+ p->scond = C_SCOND_LO;
+ p->from.type = D_REG;
+ p->from.reg = REGLINK;
+ p->to.type = D_REG;
+ p->to.reg = 3;
+
+ // BL.LO runtime.morestack(SB) // modifies LR
+ p = appendp(p);
+ p->as = ABL;
+ p->scond = C_SCOND_LO;
+ p->to.type = D_BRANCH;
+ p->to.sym = symmorestack;
+ p->cond = pmorestack;
+
+ // MOVW.W R14,$-autosize(SP)
+ p = appendp(p);
+ p->as = AMOVW;
+ p->scond |= C_WBIT;
+ p->from.type = D_REG;
+ p->from.reg = REGLINK;
+ p->to.type = D_OREG;
+ p->to.offset = -autosize;
+ p->to.reg = REGSP;
+ p->spadj = autosize;
+ } else { // > StackBig
+ // MOVW $autosize, R1
+ // MOVW $args, R2
+ // MOVW R14, R3
+ // BL runtime.morestack(SB) // modifies LR
+ // MOVW.W R14,$-autosize(SP)
+
+ // MOVW $autosize, R1
+ p = appendp(p);
+ p->as = AMOVW;
+ p->from.type = D_CONST;
+ p->from.offset = autosize;
+ p->to.type = D_REG;
+ p->to.reg = 1;
+
+ // MOVW $args, R2
+ // also need to store the extra 4 bytes.
+ p = appendp(p);
+ p->as = AMOVW;
+ p->from.type = D_CONST;
+ p->from.offset = (cursym->text->to.offset2 + 3) & ~3;
+ p->to.type = D_REG;
+ p->to.reg = 2;
+
+ // MOVW R14, R3
+ p = appendp(p);
+ p->as = AMOVW;
+ p->from.type = D_REG;
+ p->from.reg = REGLINK;
+ p->to.type = D_REG;
+ p->to.reg = 3;
+
+ // BL runtime.morestack(SB) // modifies LR
+ p = appendp(p);
+ p->as = ABL;
+ p->to.type = D_BRANCH;
+ p->to.sym = symmorestack;
+ p->cond = pmorestack;
+
+ // MOVW.W R14,$-autosize(SP)
+ p = appendp(p);
+ p->as = AMOVW;
+ p->scond |= C_WBIT;
+ p->from.type = D_REG;
+ p->from.reg = REGLINK;
+ p->to.type = D_OREG;
+ p->to.offset = -autosize;
+ p->to.reg = REGSP;
+ p->spadj = autosize;
+ }
+ break;
+
+ case ARET:
+ nocache(p);
+ if(cursym->text->mark & LEAF) {
+ if(!autosize) {
+ p->as = AB;
+ p->from = zprg.from;
+ p->to.type = D_OREG;
+ p->to.offset = 0;
+ p->to.reg = REGLINK;
+ break;
+ }
+ }
+ p->as = AMOVW;
+ p->scond |= C_PBIT;
+ p->from.type = D_OREG;
+ p->from.offset = autosize;
+ p->from.reg = REGSP;
+ p->to.type = D_REG;
+ p->to.reg = REGPC;
+ // If there are instructions following
+ // this ARET, they come from a branch
+ // with the same stackframe, so no spadj.
+ break;
+
+ case AADD:
+ if(p->from.type == D_CONST && p->from.reg == NREG && p->to.type == D_REG && p->to.reg == REGSP)
+ p->spadj = -p->from.offset;
+ break;
+
+ case ASUB:
+ if(p->from.type == D_CONST && p->from.reg == NREG && p->to.type == D_REG && p->to.reg == REGSP)
+ p->spadj = p->from.offset;
+ break;
+
+ case ADIV:
+ case ADIVU:
+ case AMOD:
+ case AMODU:
+ if(debug['M'])
+ break;
+ if(p->from.type != D_REG)
+ break;
+ if(p->to.type != D_REG)
+ break;
+ q1 = p;
+
+ /* MOV a,4(SP) */
+ q = prg();
+ q->link = p->link;
+ p->link = q;
+ p = q;
+
+ p->as = AMOVW;
+ p->line = q1->line;
+ p->from.type = D_REG;
+ p->from.reg = q1->from.reg;
+ p->to.type = D_OREG;
+ p->to.reg = REGSP;
+ p->to.offset = 4;
+
+ /* MOV b,REGTMP */
+ q = prg();
+ q->link = p->link;
+ p->link = q;
+ p = q;
+
+ p->as = AMOVW;
+ p->line = q1->line;
+ p->from.type = D_REG;
+ p->from.reg = q1->reg;
+ if(q1->reg == NREG)
+ p->from.reg = q1->to.reg;
+ p->to.type = D_REG;
+ p->to.reg = REGTMP;
+ p->to.offset = 0;
+
+ /* CALL appropriate */
+ q = prg();
+ q->link = p->link;
+ p->link = q;
+ p = q;
+
+ p->as = ABL;
+ p->line = q1->line;
+ p->to.type = D_BRANCH;
+ p->cond = p;
+ switch(o) {
+ case ADIV:
+ p->cond = prog_div;
+ p->to.sym = sym_div;
+ break;
+ case ADIVU:
+ p->cond = prog_divu;
+ p->to.sym = sym_divu;
+ break;
+ case AMOD:
+ p->cond = prog_mod;
+ p->to.sym = sym_mod;
+ break;
+ case AMODU:
+ p->cond = prog_modu;
+ p->to.sym = sym_modu;
+ break;
+ }
+
+ /* MOV REGTMP, b */
+ q = prg();
+ q->link = p->link;
+ p->link = q;
+ p = q;
+
+ p->as = AMOVW;
+ p->line = q1->line;
+ p->from.type = D_REG;
+ p->from.reg = REGTMP;
+ p->from.offset = 0;
+ p->to.type = D_REG;
+ p->to.reg = q1->to.reg;
+
+ /* ADD $8,SP */
+ q = prg();
+ q->link = p->link;
+ p->link = q;
+ p = q;
+
+ p->as = AADD;
+ p->from.type = D_CONST;
+ p->from.reg = NREG;
+ p->from.offset = 8;
+ p->reg = NREG;
+ p->to.type = D_REG;
+ p->to.reg = REGSP;
+ p->spadj = -8;
+
+ /* SUB $8,SP */
+ q1->as = ASUB;
+ q1->from.type = D_CONST;
+ q1->from.offset = 8;
+ q1->from.reg = NREG;
+ q1->reg = NREG;
+ q1->to.type = D_REG;
+ q1->to.reg = REGSP;
+ q1->spadj = 8;
+
+ break;
+ case AMOVW:
+ if((p->scond & C_WBIT) && p->to.type == D_OREG && p->to.reg == REGSP)
+ p->spadj = -p->to.offset;
+ if((p->scond & C_PBIT) && p->from.type == D_OREG && p->from.reg == REGSP && p->to.reg != REGPC)
+ p->spadj = -p->from.offset;
+ if(p->from.type == D_CONST && p->from.reg == REGSP && p->to.type == D_REG && p->to.reg == REGSP)
+ p->spadj = -p->from.offset;
+ break;
+ }
+ }
+ }
+}
+
+static void
+sigdiv(char *n)
+{
+ Sym *s;
+
+ s = lookup(n, 0);
+ if(s->type == STEXT)
+ if(s->sig == 0)
+ s->sig = SIGNINTERN;
+}
+
+void
+divsig(void)
+{
+ sigdiv("_div");
+ sigdiv("_divu");
+ sigdiv("_mod");
+ sigdiv("_modu");
+}
+
+void
+initdiv(void)
+{
+ Sym *s2, *s3, *s4, *s5;
+
+ if(prog_div != P)
+ return;
+ sym_div = s2 = lookup("_div", 0);
+ sym_divu = s3 = lookup("_divu", 0);
+ sym_mod = s4 = lookup("_mod", 0);
+ sym_modu = s5 = lookup("_modu", 0);
+ prog_div = s2->text;
+ prog_divu = s3->text;
+ prog_mod = s4->text;
+ prog_modu = s5->text;
+ if(prog_div == P) {
+ diag("undefined: %s", s2->name);
+ prog_div = cursym->text;
+ }
+ if(prog_divu == P) {
+ diag("undefined: %s", s3->name);
+ prog_divu = cursym->text;
+ }
+ if(prog_mod == P) {
+ diag("undefined: %s", s4->name);
+ prog_mod = cursym->text;
+ }
+ if(prog_modu == P) {
+ diag("undefined: %s", s5->name);
+ prog_modu = cursym->text;
+ }
+}
+
+void
+nocache(Prog *p)
+{
+ p->optab = 0;
+ p->from.class = 0;
+ p->to.class = 0;
+}
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