--- /dev/null
+// Inferno utils/5c/peep.c
+// http://code.google.com/p/inferno-os/source/browse/utils/5g/peep.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.
+
+
+#include "gg.h"
+#include "opt.h"
+
+int xtramodes(Reg*, Adr*);
+int shiftprop(Reg *r);
+void constprop(Adr *c1, Adr *v1, Reg *r);
+void predicate(void);
+int copyau1(Prog *p, Adr *v);
+
+void
+peep(void)
+{
+ Reg *r, *r1, *r2;
+ Prog *p, *p1;
+ int t;
+/*
+ * complete R structure
+ */
+ t = 0;
+ for(r=firstr; r!=R; r=r1) {
+ r1 = r->link;
+ if(r1 == R)
+ break;
+ p = r->prog->link;
+ while(p != r1->prog)
+ switch(p->as) {
+ default:
+ r2 = rega();
+ r->link = r2;
+ r2->link = r1;
+
+ r2->prog = p;
+ r2->p1 = r;
+ r->s1 = r2;
+ r2->s1 = r1;
+ r1->p1 = r2;
+
+ r = r2;
+ t++;
+
+ case ADATA:
+ case AGLOBL:
+ case ANAME:
+ case ASIGNAME:
+ p = p->link;
+ }
+ }
+
+loop1:
+ t = 0;
+ for(r=firstr; r!=R; r=r->link) {
+ p = r->prog;
+ if(p->as == ASLL || p->as == ASRL || p->as == ASRA) {
+ /*
+ * elide shift into D_SHIFT operand of subsequent instruction
+ */
+ if(shiftprop(r)) {
+ excise(r);
+ t++;
+ }
+ }
+ if(p->as == AMOVW || p->as == AMOVF || p->as == AMOVD)
+ if(regtyp(&p->to)) {
+ if(p->from.type == D_CONST)
+ constprop(&p->from, &p->to, r->s1);
+ else
+ if(regtyp(&p->from))
+ if(p->from.type == p->to.type) {
+ if(copyprop(r)) {
+ excise(r);
+ t++;
+ } else
+ if(subprop(r) && copyprop(r)) {
+ excise(r);
+ t++;
+ }
+ }
+ }
+ }
+ if(t)
+ goto loop1;
+ /*
+ * look for MOVB x,R; MOVB R,R
+ */
+ for(r=firstr; r!=R; r=r->link) {
+ p = r->prog;
+ switch(p->as) {
+ default:
+ continue;
+ case AEOR:
+ /*
+ * EOR -1,x,y => MVN x,y
+ */
+ if(p->from.type == D_CONST && p->from.offset == -1) {
+ p->as = AMVN;
+ p->from.type = D_REG;
+ if(p->reg != NREG)
+ p->from.reg = p->reg;
+ else
+ p->from.reg = p->to.reg;
+ p->reg = NREG;
+ }
+ continue;
+ case AMOVH:
+ case AMOVHU:
+ case AMOVB:
+ case AMOVBU:
+ if(p->to.type != D_REG)
+ continue;
+ break;
+ }
+ r1 = r->link;
+ if(r1 == R)
+ continue;
+ p1 = r1->prog;
+ if(p1->as != p->as)
+ continue;
+ if(p1->from.type != D_REG || p1->from.reg != p->to.reg)
+ continue;
+ if(p1->to.type != D_REG || p1->to.reg != p->to.reg)
+ continue;
+ excise(r1);
+ }
+
+ for(r=firstr; r!=R; r=r->link) {
+ p = r->prog;
+ switch(p->as) {
+ case AMOVW:
+ case AMOVB:
+ case AMOVBU:
+ if(p->from.type == D_OREG && p->from.offset == 0)
+ xtramodes(r, &p->from);
+ else if(p->to.type == D_OREG && p->to.offset == 0)
+ xtramodes(r, &p->to);
+ else
+ continue;
+ break;
+ case ACMP:
+ /*
+ * elide CMP $0,x if calculation of x can set condition codes
+ */
+ if(p->from.type != D_CONST || p->from.offset != 0)
+ continue;
+ r2 = r->s1;
+ if(r2 == R)
+ continue;
+ t = r2->prog->as;
+ switch(t) {
+ default:
+ continue;
+ case ABEQ:
+ case ABNE:
+ case ABMI:
+ case ABPL:
+ break;
+ case ABGE:
+ t = ABPL;
+ break;
+ case ABLT:
+ t = ABMI;
+ break;
+ case ABHI:
+ t = ABNE;
+ break;
+ case ABLS:
+ t = ABEQ;
+ break;
+ }
+ r1 = r;
+ do
+ r1 = uniqp(r1);
+ while (r1 != R && r1->prog->as == ANOP);
+ if(r1 == R)
+ continue;
+ p1 = r1->prog;
+ if(p1->to.type != D_REG)
+ continue;
+ if(p1->to.reg != p->reg)
+ if(!(p1->as == AMOVW && p1->from.type == D_REG && p1->from.reg == p->reg))
+ continue;
+ switch(p1->as) {
+ default:
+ continue;
+ case AMOVW:
+ if(p1->from.type != D_REG)
+ continue;
+ case AAND:
+ case AEOR:
+ case AORR:
+ case ABIC:
+ case AMVN:
+ case ASUB:
+ case ARSB:
+ case AADD:
+ case AADC:
+ case ASBC:
+ case ARSC:
+ break;
+ }
+ p1->scond |= C_SBIT;
+ r2->prog->as = t;
+ excise(r);
+ continue;
+ }
+ }
+
+ predicate();
+}
+
+Reg*
+uniqp(Reg *r)
+{
+ Reg *r1;
+
+ r1 = r->p1;
+ if(r1 == R) {
+ r1 = r->p2;
+ if(r1 == R || r1->p2link != R)
+ return R;
+ } else
+ if(r->p2 != R)
+ return R;
+ return r1;
+}
+
+Reg*
+uniqs(Reg *r)
+{
+ Reg *r1;
+
+ r1 = r->s1;
+ if(r1 == R) {
+ r1 = r->s2;
+ if(r1 == R)
+ return R;
+ } else
+ if(r->s2 != R)
+ return R;
+ return r1;
+}
+
+int
+regtyp(Adr *a)
+{
+
+ if(a->type == D_REG)
+ return 1;
+ if(a->type == D_FREG)
+ return 1;
+ return 0;
+}
+
+/*
+ * the idea is to substitute
+ * one register for another
+ * from one MOV to another
+ * MOV a, R0
+ * ADD b, R0 / no use of R1
+ * MOV R0, R1
+ * would be converted to
+ * MOV a, R1
+ * ADD b, R1
+ * MOV R1, R0
+ * hopefully, then the former or latter MOV
+ * will be eliminated by copy propagation.
+ */
+int
+subprop(Reg *r0)
+{
+ Prog *p;
+ Adr *v1, *v2;
+ Reg *r;
+ int t;
+
+ p = r0->prog;
+ v1 = &p->from;
+ if(!regtyp(v1))
+ return 0;
+ v2 = &p->to;
+ if(!regtyp(v2))
+ return 0;
+ for(r=uniqp(r0); r!=R; r=uniqp(r)) {
+ if(uniqs(r) == R)
+ break;
+ p = r->prog;
+ switch(p->as) {
+ case ABL:
+ return 0;
+
+ case ACMP:
+ case ACMN:
+ case AADD:
+ case ASUB:
+ case ARSB:
+ case ASLL:
+ case ASRL:
+ case ASRA:
+ case AORR:
+ case AAND:
+ case AEOR:
+ case AMUL:
+ case ADIV:
+ case ADIVU:
+
+ case ACMPF:
+ case ACMPD:
+ case AADDD:
+ case AADDF:
+ case ASUBD:
+ case ASUBF:
+ case AMULD:
+ case AMULF:
+ case ADIVD:
+ case ADIVF:
+ if(p->to.type == v1->type)
+ if(p->to.reg == v1->reg) {
+ if(p->reg == NREG)
+ p->reg = p->to.reg;
+ goto gotit;
+ }
+ break;
+
+ case AMOVF:
+ case AMOVD:
+ case AMOVW:
+ if(p->to.type == v1->type)
+ if(p->to.reg == v1->reg)
+ goto gotit;
+ break;
+
+ case AMOVM:
+ t = 1<<v2->reg;
+ if((p->from.type == D_CONST && (p->from.offset&t)) ||
+ (p->to.type == D_CONST && (p->to.offset&t)))
+ return 0;
+ break;
+ }
+ if(copyau(&p->from, v2) ||
+ copyau1(p, v2) ||
+ copyau(&p->to, v2))
+ break;
+ if(copysub(&p->from, v1, v2, 0) ||
+ copysub1(p, v1, v2, 0) ||
+ copysub(&p->to, v1, v2, 0))
+ break;
+ }
+ return 0;
+
+gotit:
+ copysub(&p->to, v1, v2, 1);
+ if(debug['P']) {
+ print("gotit: %D->%D\n%P", v1, v2, r->prog);
+ if(p->from.type == v2->type)
+ print(" excise");
+ print("\n");
+ }
+ for(r=uniqs(r); r!=r0; r=uniqs(r)) {
+ p = r->prog;
+ copysub(&p->from, v1, v2, 1);
+ copysub1(p, v1, v2, 1);
+ copysub(&p->to, v1, v2, 1);
+ if(debug['P'])
+ print("%P\n", r->prog);
+ }
+ t = v1->reg;
+ v1->reg = v2->reg;
+ v2->reg = t;
+ if(debug['P'])
+ print("%P last\n", r->prog);
+ return 1;
+}
+
+/*
+ * The idea is to remove redundant copies.
+ * v1->v2 F=0
+ * (use v2 s/v2/v1/)*
+ * set v1 F=1
+ * use v2 return fail
+ * -----------------
+ * v1->v2 F=0
+ * (use v2 s/v2/v1/)*
+ * set v1 F=1
+ * set v2 return success
+ */
+int
+copyprop(Reg *r0)
+{
+ Prog *p;
+ Adr *v1, *v2;
+ Reg *r;
+
+ p = r0->prog;
+ v1 = &p->from;
+ v2 = &p->to;
+ if(copyas(v1, v2))
+ return 1;
+ for(r=firstr; r!=R; r=r->link)
+ r->active = 0;
+ return copy1(v1, v2, r0->s1, 0);
+}
+
+int
+copy1(Adr *v1, Adr *v2, Reg *r, int f)
+{
+ int t;
+ Prog *p;
+
+ if(r->active) {
+ if(debug['P'])
+ print("act set; return 1\n");
+ return 1;
+ }
+ r->active = 1;
+ if(debug['P'])
+ print("copy %D->%D f=%d\n", v1, v2, f);
+ for(; r != R; r = r->s1) {
+ p = r->prog;
+ if(debug['P'])
+ print("%P", p);
+ if(!f && uniqp(r) == R) {
+ f = 1;
+ if(debug['P'])
+ print("; merge; f=%d", f);
+ }
+ t = copyu(p, v2, A);
+ switch(t) {
+ case 2: /* rar, cant split */
+ if(debug['P'])
+ print("; %Drar; return 0\n", v2);
+ return 0;
+
+ case 3: /* set */
+ if(debug['P'])
+ print("; %Dset; return 1\n", v2);
+ return 1;
+
+ case 1: /* used, substitute */
+ case 4: /* use and set */
+ if(f) {
+ if(!debug['P'])
+ return 0;
+ if(t == 4)
+ print("; %Dused+set and f=%d; return 0\n", v2, f);
+ else
+ print("; %Dused and f=%d; return 0\n", v2, f);
+ return 0;
+ }
+ if(copyu(p, v2, v1)) {
+ if(debug['P'])
+ print("; sub fail; return 0\n");
+ return 0;
+ }
+ if(debug['P'])
+ print("; sub%D/%D", v2, v1);
+ if(t == 4) {
+ if(debug['P'])
+ print("; %Dused+set; return 1\n", v2);
+ return 1;
+ }
+ break;
+ }
+ if(!f) {
+ t = copyu(p, v1, A);
+ if(!f && (t == 2 || t == 3 || t == 4)) {
+ f = 1;
+ if(debug['P'])
+ print("; %Dset and !f; f=%d", v1, f);
+ }
+ }
+ if(debug['P'])
+ print("\n");
+ if(r->s2)
+ if(!copy1(v1, v2, r->s2, f))
+ return 0;
+ }
+ return 1;
+}
+
+/*
+ * The idea is to remove redundant constants.
+ * $c1->v1
+ * ($c1->v2 s/$c1/v1)*
+ * set v1 return
+ * The v1->v2 should be eliminated by copy propagation.
+ */
+void
+constprop(Adr *c1, Adr *v1, Reg *r)
+{
+ Prog *p;
+
+ if(debug['P'])
+ print("constprop %D->%D\n", c1, v1);
+ for(; r != R; r = r->s1) {
+ p = r->prog;
+ if(debug['P'])
+ print("%P", p);
+ if(uniqp(r) == R) {
+ if(debug['P'])
+ print("; merge; return\n");
+ return;
+ }
+ if(p->as == AMOVW && copyas(&p->from, c1)) {
+ if(debug['P'])
+ print("; sub%D/%D", &p->from, v1);
+ p->from = *v1;
+ } else if(copyu(p, v1, A) > 1) {
+ if(debug['P'])
+ print("; %Dset; return\n", v1);
+ return;
+ }
+ if(debug['P'])
+ print("\n");
+ if(r->s2)
+ constprop(c1, v1, r->s2);
+ }
+}
+
+/*
+ * ASLL x,y,w
+ * .. (not use w, not set x y w)
+ * AXXX w,a,b (a != w)
+ * .. (not use w)
+ * (set w)
+ * ----------- changed to
+ * ..
+ * AXXX (x<<y),a,b
+ * ..
+ */
+#define FAIL(msg) { if(debug['P']) print("\t%s; FAILURE\n", msg); return 0; }
+int
+shiftprop(Reg *r)
+{
+ Reg *r1;
+ Prog *p, *p1, *p2;
+ int n, o;
+ Adr a;
+
+ p = r->prog;
+ if(p->to.type != D_REG)
+ FAIL("BOTCH: result not reg");
+ n = p->to.reg;
+ a = zprog.from;
+ if(p->reg != NREG && p->reg != p->to.reg) {
+ a.type = D_REG;
+ a.reg = p->reg;
+ }
+ if(debug['P'])
+ print("shiftprop\n%P", p);
+ r1 = r;
+ for(;;) {
+ /* find first use of shift result; abort if shift operands or result are changed */
+ r1 = uniqs(r1);
+ if(r1 == R)
+ FAIL("branch");
+ if(uniqp(r1) == R)
+ FAIL("merge");
+ p1 = r1->prog;
+ if(debug['P'])
+ print("\n%P", p1);
+ switch(copyu(p1, &p->to, A)) {
+ case 0: /* not used or set */
+ if((p->from.type == D_REG && copyu(p1, &p->from, A) > 1) ||
+ (a.type == D_REG && copyu(p1, &a, A) > 1))
+ FAIL("args modified");
+ continue;
+ case 3: /* set, not used */
+ FAIL("BOTCH: noref");
+ }
+ break;
+ }
+ /* check whether substitution can be done */
+ switch(p1->as) {
+ default:
+ FAIL("non-dpi");
+ case AAND:
+ case AEOR:
+ case AADD:
+ case AADC:
+ case AORR:
+ case ASUB:
+ case ARSB:
+ case ASBC:
+ case ARSC:
+ if(p1->reg == n || (p1->reg == NREG && p1->to.type == D_REG && p1->to.reg == n)) {
+ if(p1->from.type != D_REG)
+ FAIL("can't swap");
+ p1->reg = p1->from.reg;
+ p1->from.reg = n;
+ switch(p1->as) {
+ case ASUB:
+ p1->as = ARSB;
+ break;
+ case ARSB:
+ p1->as = ASUB;
+ break;
+ case ASBC:
+ p1->as = ARSC;
+ break;
+ case ARSC:
+ p1->as = ASBC;
+ break;
+ }
+ if(debug['P'])
+ print("\t=>%P", p1);
+ }
+ case ABIC:
+ case ACMP:
+ case ACMN:
+ if(p1->reg == n)
+ FAIL("can't swap");
+ if(p1->reg == NREG && p1->to.reg == n)
+ FAIL("shift result used twice");
+ case AMVN:
+ if(p1->from.type == D_SHIFT)
+ FAIL("shift result used in shift");
+ if(p1->from.type != D_REG || p1->from.reg != n)
+ FAIL("BOTCH: where is it used?");
+ break;
+ }
+ /* check whether shift result is used subsequently */
+ p2 = p1;
+ if(p1->to.reg != n)
+ for (;;) {
+ r1 = uniqs(r1);
+ if(r1 == R)
+ FAIL("inconclusive");
+ p1 = r1->prog;
+ if(debug['P'])
+ print("\n%P", p1);
+ switch(copyu(p1, &p->to, A)) {
+ case 0: /* not used or set */
+ continue;
+ case 3: /* set, not used */
+ break;
+ default:/* used */
+ FAIL("reused");
+ }
+ break;
+ }
+ /* make the substitution */
+ p2->from.type = D_SHIFT;
+ p2->from.reg = NREG;
+ o = p->reg;
+ if(o == NREG)
+ o = p->to.reg;
+ switch(p->from.type){
+ case D_CONST:
+ o |= (p->from.offset&0x1f)<<7;
+ break;
+ case D_REG:
+ o |= (1<<4) | (p->from.reg<<8);
+ break;
+ }
+ switch(p->as){
+ case ASLL:
+ o |= 0<<5;
+ break;
+ case ASRL:
+ o |= 1<<5;
+ break;
+ case ASRA:
+ o |= 2<<5;
+ break;
+ }
+ p2->from.offset = o;
+ if(debug['P'])
+ print("\t=>%P\tSUCCEED\n", p2);
+ return 1;
+}
+
+Reg*
+findpre(Reg *r, Adr *v)
+{
+ Reg *r1;
+
+ for(r1=uniqp(r); r1!=R; r=r1,r1=uniqp(r)) {
+ if(uniqs(r1) != r)
+ return R;
+ switch(copyu(r1->prog, v, A)) {
+ case 1: /* used */
+ case 2: /* read-alter-rewrite */
+ return R;
+ case 3: /* set */
+ case 4: /* set and used */
+ return r1;
+ }
+ }
+ return R;
+}
+
+Reg*
+findinc(Reg *r, Reg *r2, Adr *v)
+{
+ Reg *r1;
+ Prog *p;
+
+
+ for(r1=uniqs(r); r1!=R && r1!=r2; r=r1,r1=uniqs(r)) {
+ if(uniqp(r1) != r)
+ return R;
+ switch(copyu(r1->prog, v, A)) {
+ case 0: /* not touched */
+ continue;
+ case 4: /* set and used */
+ p = r1->prog;
+ if(p->as == AADD)
+ if(p->from.type == D_CONST)
+ if(p->from.offset > -4096 && p->from.offset < 4096)
+ return r1;
+ default:
+ return R;
+ }
+ }
+ return R;
+}
+
+int
+nochange(Reg *r, Reg *r2, Prog *p)
+{
+ Adr a[3];
+ int i, n;
+
+ if(r == r2)
+ return 1;
+ n = 0;
+ if(p->reg != NREG && p->reg != p->to.reg) {
+ a[n].type = D_REG;
+ a[n++].reg = p->reg;
+ }
+ switch(p->from.type) {
+ case D_SHIFT:
+ a[n].type = D_REG;
+ a[n++].reg = p->from.offset&0xf;
+ case D_REG:
+ a[n].type = D_REG;
+ a[n++].reg = p->from.reg;
+ }
+ if(n == 0)
+ return 1;
+ for(; r!=R && r!=r2; r=uniqs(r)) {
+ p = r->prog;
+ for(i=0; i<n; i++)
+ if(copyu(p, &a[i], A) > 1)
+ return 0;
+ }
+ return 1;
+}
+
+int
+findu1(Reg *r, Adr *v)
+{
+ for(; r != R; r = r->s1) {
+ if(r->active)
+ return 0;
+ r->active = 1;
+ switch(copyu(r->prog, v, A)) {
+ case 1: /* used */
+ case 2: /* read-alter-rewrite */
+ case 4: /* set and used */
+ return 1;
+ case 3: /* set */
+ return 0;
+ }
+ if(r->s2)
+ if (findu1(r->s2, v))
+ return 1;
+ }
+ return 0;
+}
+
+int
+finduse(Reg *r, Adr *v)
+{
+ Reg *r1;
+
+ for(r1=firstr; r1!=R; r1=r1->link)
+ r1->active = 0;
+ return findu1(r, v);
+}
+
+int
+xtramodes(Reg *r, Adr *a)
+{
+ Reg *r1, *r2, *r3;
+ Prog *p, *p1;
+ Adr v;
+
+ p = r->prog;
+ if(debug['h'] && p->as == AMOVB && p->from.type == D_OREG) /* byte load */
+ return 0;
+ v = *a;
+ v.type = D_REG;
+ r1 = findpre(r, &v);
+ if(r1 != R) {
+ p1 = r1->prog;
+ if(p1->to.type == D_REG && p1->to.reg == v.reg)
+ switch(p1->as) {
+ case AADD:
+ if(p1->from.type == D_REG ||
+ (p1->from.type == D_SHIFT && (p1->from.offset&(1<<4)) == 0 &&
+ (p->as != AMOVB || (a == &p->from && (p1->from.offset&~0xf) == 0))) ||
+ (p1->from.type == D_CONST &&
+ p1->from.offset > -4096 && p1->from.offset < 4096))
+ if(nochange(uniqs(r1), r, p1)) {
+ if(a != &p->from || v.reg != p->to.reg)
+ if (finduse(r->s1, &v)) {
+ if(p1->reg == NREG || p1->reg == v.reg)
+ /* pre-indexing */
+ p->scond |= C_WBIT;
+ else return 0;
+ }
+ switch (p1->from.type) {
+ case D_REG:
+ /* register offset */
+ a->type = D_SHIFT;
+ a->offset = p1->from.reg;
+ break;
+ case D_SHIFT:
+ /* scaled register offset */
+ a->type = D_SHIFT;
+ case D_CONST:
+ /* immediate offset */
+ a->offset = p1->from.offset;
+ break;
+ }
+ if(p1->reg != NREG)
+ a->reg = p1->reg;
+ excise(r1);
+ return 1;
+ }
+ break;
+ case AMOVW:
+ if(p1->from.type == D_REG)
+ if((r2 = findinc(r1, r, &p1->from)) != R) {
+ for(r3=uniqs(r2); r3->prog->as==ANOP; r3=uniqs(r3))
+ ;
+ if(r3 == r) {
+ /* post-indexing */
+ p1 = r2->prog;
+ a->reg = p1->to.reg;
+ a->offset = p1->from.offset;
+ p->scond |= C_PBIT;
+ if(!finduse(r, &r1->prog->to))
+ excise(r1);
+ excise(r2);
+ return 1;
+ }
+ }
+ break;
+ }
+ }
+ if(a != &p->from || a->reg != p->to.reg)
+ if((r1 = findinc(r, R, &v)) != R) {
+ /* post-indexing */
+ p1 = r1->prog;
+ a->offset = p1->from.offset;
+ p->scond |= C_PBIT;
+ excise(r1);
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * return
+ * 1 if v only used (and substitute),
+ * 2 if read-alter-rewrite
+ * 3 if set
+ * 4 if set and used
+ * 0 otherwise (not touched)
+ */
+int
+copyu(Prog *p, Adr *v, Adr *s)
+{
+
+ switch(p->as) {
+
+ default:
+ if(debug['P'])
+ print(" (?)");
+ return 2;
+
+ case AMOVM:
+ if(v->type != D_REG)
+ return 0;
+ if(p->from.type == D_CONST) { /* read reglist, read/rar */
+ if(s != A) {
+ if(p->from.offset&(1<<v->reg))
+ return 1;
+ if(copysub(&p->to, v, s, 1))
+ return 1;
+ return 0;
+ }
+ if(copyau(&p->to, v)) {
+ if(p->scond&C_WBIT)
+ return 2;
+ return 1;
+ }
+ if(p->from.offset&(1<<v->reg))
+ return 1;
+ } else { /* read/rar, write reglist */
+ if(s != A) {
+ if(p->to.offset&(1<<v->reg))
+ return 1;
+ if(copysub(&p->from, v, s, 1))
+ return 1;
+ return 0;
+ }
+ if(copyau(&p->from, v)) {
+ if(p->scond&C_WBIT)
+ return 2;
+ if(p->to.offset&(1<<v->reg))
+ return 4;
+ return 1;
+ }
+ if(p->to.offset&(1<<v->reg))
+ return 3;
+ }
+ return 0;
+
+ case ANOP: /* read, write */
+ case AMOVW:
+ case AMOVF:
+ case AMOVD:
+ case AMOVH:
+ case AMOVHU:
+ case AMOVB:
+ case AMOVBU:
+ case AMOVDW:
+ case AMOVWD:
+ case AMOVFD:
+ case AMOVDF:
+ if(p->scond&(C_WBIT|C_PBIT))
+ if(v->type == D_REG) {
+ if(p->from.type == D_OREG || p->from.type == D_SHIFT) {
+ if(p->from.reg == v->reg)
+ return 2;
+ } else {
+ if(p->to.reg == v->reg)
+ return 2;
+ }
+ }
+ if(s != A) {
+ if(copysub(&p->from, v, s, 1))
+ return 1;
+ if(!copyas(&p->to, v))
+ if(copysub(&p->to, v, s, 1))
+ return 1;
+ return 0;
+ }
+ if(copyas(&p->to, v)) {
+ if(copyau(&p->from, v))
+ return 4;
+ return 3;
+ }
+ if(copyau(&p->from, v))
+ return 1;
+ if(copyau(&p->to, v))
+ return 1;
+ return 0;
+
+
+ case AADD: /* read, read, write */
+ case ASUB:
+ case ARSB:
+ case ASLL:
+ case ASRL:
+ case ASRA:
+ case AORR:
+ case AAND:
+ case AEOR:
+ case AMUL:
+ case ADIV:
+ case ADIVU:
+ case AADDF:
+ case AADDD:
+ case ASUBF:
+ case ASUBD:
+ case AMULF:
+ case AMULD:
+ case ADIVF:
+ case ADIVD:
+
+ case ACMPF:
+ case ACMPD:
+ case ACMP:
+ case ACMN:
+ case ACASE:
+ if(s != A) {
+ if(copysub(&p->from, v, s, 1))
+ return 1;
+ if(copysub1(p, v, s, 1))
+ return 1;
+ if(!copyas(&p->to, v))
+ if(copysub(&p->to, v, s, 1))
+ return 1;
+ return 0;
+ }
+ if(copyas(&p->to, v)) {
+ if(p->reg == NREG)
+ p->reg = p->to.reg;
+ if(copyau(&p->from, v))
+ return 4;
+ if(copyau1(p, v))
+ return 4;
+ return 3;
+ }
+ if(copyau(&p->from, v))
+ return 1;
+ if(copyau1(p, v))
+ return 1;
+ if(copyau(&p->to, v))
+ return 1;
+ return 0;
+
+ case ABEQ: /* read, read */
+ 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:
+ if(s != A) {
+ if(copysub(&p->from, v, s, 1))
+ return 1;
+ return copysub1(p, v, s, 1);
+ }
+ if(copyau(&p->from, v))
+ return 1;
+ if(copyau1(p, v))
+ return 1;
+ return 0;
+
+ case AB: /* funny */
+ if(s != A) {
+ if(copysub(&p->to, v, s, 1))
+ return 1;
+ return 0;
+ }
+ if(copyau(&p->to, v))
+ return 1;
+ return 0;
+
+ case ARET: /* funny */
+ if(v->type == D_REG)
+ if(v->reg == REGRET)
+ return 2;
+ if(v->type == D_FREG)
+ if(v->reg == FREGRET)
+ return 2;
+
+ case ABL: /* funny */
+ if(v->type == D_REG) {
+ if(v->reg <= REGEXT && v->reg > exregoffset)
+ return 2;
+ if(v->reg == REGARG)
+ return 2;
+ }
+ if(v->type == D_FREG)
+ if(v->reg <= FREGEXT && v->reg > exfregoffset)
+ return 2;
+
+ if(s != A) {
+ if(copysub(&p->to, v, s, 1))
+ return 1;
+ return 0;
+ }
+ if(copyau(&p->to, v))
+ return 4;
+ return 3;
+
+ case ATEXT: /* funny */
+ if(v->type == D_REG)
+ if(v->reg == REGARG)
+ return 3;
+ return 0;
+ }
+ return 0;
+}
+
+int
+a2type(Prog *p)
+{
+
+ switch(p->as) {
+
+ case ACMP:
+ case ACMN:
+
+ case AADD:
+ case ASUB:
+ case ARSB:
+ case ASLL:
+ case ASRL:
+ case ASRA:
+ case AORR:
+ case AAND:
+ case AEOR:
+ case AMUL:
+ case ADIV:
+ case ADIVU:
+ return D_REG;
+
+ case ACMPF:
+ case ACMPD:
+
+ case AADDF:
+ case AADDD:
+ case ASUBF:
+ case ASUBD:
+ case AMULF:
+ case AMULD:
+ case ADIVF:
+ case ADIVD:
+ return D_FREG;
+ }
+ return D_NONE;
+}
+
+/*
+ * direct reference,
+ * could be set/use depending on
+ * semantics
+ */
+int
+copyas(Adr *a, Adr *v)
+{
+
+ if(regtyp(v)) {
+ if(a->type == v->type)
+ if(a->reg == v->reg)
+ return 1;
+ } else
+ if(v->type == D_CONST) { /* for constprop */
+ if(a->type == v->type)
+ if(a->name == v->name)
+ if(a->sym == v->sym)
+ if(a->reg == v->reg)
+ if(a->offset == v->offset)
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * either direct or indirect
+ */
+int
+copyau(Adr *a, Adr *v)
+{
+
+ if(copyas(a, v))
+ return 1;
+ if(v->type == D_REG) {
+ if(a->type == D_OREG) {
+ if(v->reg == a->reg)
+ return 1;
+ } else
+ if(a->type == D_REGREG) {
+ if(v->reg == a->reg)
+ return 1;
+ if(a->offset == v->reg)
+ return 1;
+ } else
+ if(a->type == D_SHIFT) {
+ if((a->offset&0xf) == v->reg)
+ return 1;
+ if((a->offset&(1<<4)) && (a->offset>>8) == v->reg)
+ return 1;
+ }
+ }
+ return 0;
+}
+
+int
+copyau1(Prog *p, Adr *v)
+{
+
+ if(regtyp(v)) {
+ if(a2type(p) == v->type)
+ if(p->reg == v->reg) {
+ if(a2type(p) != v->type)
+ print("botch a2type %P\n", p);
+ return 1;
+ }
+ }
+ return 0;
+}
+
+/*
+ * substitute s for v in a
+ * return failure to substitute
+ */
+int
+copysub(Adr *a, Adr *v, Adr *s, int f)
+{
+
+ if(f)
+ if(copyau(a, v)) {
+ if(a->type == D_SHIFT) {
+ if((a->offset&0xf) == v->reg)
+ a->offset = (a->offset&~0xf)|s->reg;
+ if((a->offset&(1<<4)) && (a->offset>>8) == v->reg)
+ a->offset = (a->offset&~(0xf<<8))|(s->reg<<8);
+ } else
+ if(a->type == D_REGREG) {
+ if(a->offset == v->reg)
+ a->offset = s->reg;
+ if(a->reg == v->reg)
+ a->reg = s->reg;
+ } else
+ a->reg = s->reg;
+ }
+ return 0;
+}
+
+int
+copysub1(Prog *p1, Adr *v, Adr *s, int f)
+{
+
+ if(f)
+ if(copyau1(p1, v))
+ p1->reg = s->reg;
+ return 0;
+}
+
+struct {
+ int opcode;
+ int notopcode;
+ int scond;
+ int notscond;
+} predinfo[] = {
+ { ABEQ, ABNE, 0x0, 0x1, },
+ { ABNE, ABEQ, 0x1, 0x0, },
+ { ABCS, ABCC, 0x2, 0x3, },
+ { ABHS, ABLO, 0x2, 0x3, },
+ { ABCC, ABCS, 0x3, 0x2, },
+ { ABLO, ABHS, 0x3, 0x2, },
+ { ABMI, ABPL, 0x4, 0x5, },
+ { ABPL, ABMI, 0x5, 0x4, },
+ { ABVS, ABVC, 0x6, 0x7, },
+ { ABVC, ABVS, 0x7, 0x6, },
+ { ABHI, ABLS, 0x8, 0x9, },
+ { ABLS, ABHI, 0x9, 0x8, },
+ { ABGE, ABLT, 0xA, 0xB, },
+ { ABLT, ABGE, 0xB, 0xA, },
+ { ABGT, ABLE, 0xC, 0xD, },
+ { ABLE, ABGT, 0xD, 0xC, },
+};
+
+typedef struct {
+ Reg *start;
+ Reg *last;
+ Reg *end;
+ int len;
+} Joininfo;
+
+enum {
+ Join,
+ Split,
+ End,
+ Branch,
+ Setcond,
+ Toolong
+};
+
+enum {
+ Falsecond,
+ Truecond,
+ Delbranch,
+ Keepbranch
+};
+
+int
+isbranch(Prog *p)
+{
+ return (ABEQ <= p->as) && (p->as <= ABLE);
+}
+
+int
+predicable(Prog *p)
+{
+ if (isbranch(p)
+ || p->as == ANOP
+ || p->as == AXXX
+ || p->as == ADATA
+ || p->as == AGLOBL
+ || p->as == AGOK
+ || p->as == AHISTORY
+ || p->as == ANAME
+ || p->as == ASIGNAME
+ || p->as == ATEXT
+ || p->as == AWORD
+ || p->as == ABCASE
+ || p->as == ACASE)
+ return 0;
+ return 1;
+}
+
+/*
+ * Depends on an analysis of the encodings performed by 5l.
+ * These seem to be all of the opcodes that lead to the "S" bit
+ * being set in the instruction encodings.
+ *
+ * C_SBIT may also have been set explicitly in p->scond.
+ */
+int
+modifiescpsr(Prog *p)
+{
+ return (p->scond&C_SBIT)
+ || p->as == ATST
+ || p->as == ATEQ
+ || p->as == ACMN
+ || p->as == ACMP
+ || p->as == AMULU
+ || p->as == ADIVU
+ || p->as == AMUL
+ || p->as == ADIV
+ || p->as == AMOD
+ || p->as == AMODU
+ || p->as == ABL;
+}
+
+/*
+ * Find the maximal chain of instructions starting with r which could
+ * be executed conditionally
+ */
+int
+joinsplit(Reg *r, Joininfo *j)
+{
+ j->start = r;
+ j->last = r;
+ j->len = 0;
+ do {
+ if (r->p2 && (r->p1 || r->p2->p2link)) {
+ j->end = r;
+ return Join;
+ }
+ if (r->s1 && r->s2) {
+ j->end = r;
+ return Split;
+ }
+ j->last = r;
+ if (r->prog->as != ANOP)
+ j->len++;
+ if (!r->s1 && !r->s2) {
+ j->end = r->link;
+ return End;
+ }
+ if (r->s2) {
+ j->end = r->s2;
+ return Branch;
+ }
+ if (modifiescpsr(r->prog)) {
+ j->end = r->s1;
+ return Setcond;
+ }
+ r = r->s1;
+ } while (j->len < 4);
+ j->end = r;
+ return Toolong;
+}
+
+Reg *
+successor(Reg *r)
+{
+ if (r->s1)
+ return r->s1;
+ else
+ return r->s2;
+}
+
+void
+applypred(Reg *rstart, Joininfo *j, int cond, int branch)
+{
+ int pred;
+ Reg *r;
+
+ if(j->len == 0)
+ return;
+ if (cond == Truecond)
+ pred = predinfo[rstart->prog->as - ABEQ].scond;
+ else
+ pred = predinfo[rstart->prog->as - ABEQ].notscond;
+
+ for (r = j->start; ; r = successor(r)) {
+ if (r->prog->as == AB) {
+ if (r != j->last || branch == Delbranch)
+ excise(r);
+ else {
+ if (cond == Truecond)
+ r->prog->as = predinfo[rstart->prog->as - ABEQ].opcode;
+ else
+ r->prog->as = predinfo[rstart->prog->as - ABEQ].notopcode;
+ }
+ }
+ else if (predicable(r->prog))
+ r->prog->scond = (r->prog->scond&~C_SCOND)|pred;
+ if (r->s1 != r->link) {
+ r->s1 = r->link;
+ r->link->p1 = r;
+ }
+ if (r == j->last)
+ break;
+ }
+}
+
+void
+predicate(void)
+{
+ Reg *r;
+ int t1, t2;
+ Joininfo j1, j2;
+
+ for(r=firstr; r!=R; r=r->link) {
+ if (isbranch(r->prog)) {
+ t1 = joinsplit(r->s1, &j1);
+ t2 = joinsplit(r->s2, &j2);
+ if(j1.last->link != j2.start)
+ continue;
+ if(j1.end == j2.end)
+ if((t1 == Branch && (t2 == Join || t2 == Setcond)) ||
+ (t2 == Join && (t1 == Join || t1 == Setcond))) {
+ applypred(r, &j1, Falsecond, Delbranch);
+ applypred(r, &j2, Truecond, Delbranch);
+ excise(r);
+ continue;
+ }
+ if(t1 == End || t1 == Branch) {
+ applypred(r, &j1, Falsecond, Keepbranch);
+ excise(r);
+ continue;
+ }
+ }
+ }
+}