From d8b4e87af669c2b260686a5db67f7f02b4c164d9 Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Sun, 14 Dec 2025 12:15:59 +0100
Subject: various relocation related optimization

With 59ca5a8db, querying if a symbol is defined is cheap. If we're
compiling code that calls foo() and we defined foo() in this compilation
unit, we already know its offset within the .text section, so use it
instead of emitting a relocation for the linker to handle.  Also, put
small literal data in the .text section instead of .rodata.  This seems
to improve performance (cache locality?), and as a bonus, it will be
good for aarch64's instr encoding with smallish PC-relative offsets.
---
 x86_64/emit.c | 45 +++++++++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 16 deletions(-)

(limited to 'x86_64/emit.c')

diff --git a/x86_64/emit.c b/x86_64/emit.c
index 2f7db11..6e832a4 100644
--- a/x86_64/emit.c
+++ b/x86_64/emit.c
@@ -118,8 +118,6 @@ mkimmdatregoper(union ref r)
    return ref2oper(r);
 }
 
-static int rbpoff;
-
 static struct oper
 mkmemoper(union ref r)
 {
@@ -252,6 +250,7 @@ opermatch(enum operpat pat, struct oper oper)
 #define DS(S) D(S, sizeof S - 1)
 
 static bool usebp; /* use RBP? */
+static int rbpoff;
 static const char *curfnsym;
 static uchar *fnstart;
 
@@ -333,21 +332,29 @@ encode(uchar **pcode, const struct desc *tab, int ntab, enum irclass k, struct o
          if (mem.cindex == NOINDEX) {
             /* %rip(var) */
             static uchar offs[NOPERENC] = { [EN_MI8] = 1, [EN_MI16] = 2, [EN_MI32] = 4 };
-            enum relockind r;
-            if ((!conht[mem.con].deref && ccopt.pic) || conht[mem.con].isfunc)
-               r = (rex ? REL_GOTPCRELX_REX : REL_GOTPCRELX);
-            else
-               r = REL_PCREL32;
+            uint addr;
+            int disp = mem.disp - 4 - offs[en->operenc];
+            const char *sym = xcon2sym(mem.con);
             B(/*mod 0*/ (reg & 7) << 3 | RBP);
-            objreloc(xcon2sym(mem.con), r, Stext, *pcode - objout.textbegin, mem.disp - 4 - offs[en->operenc]);
+            if (objhassym(sym, &addr) == Stext) {
+               I32(addr - (*pcode - objout.textbegin) + disp);
+            } else {
+               enum relockind r;
+               if ((!conht[mem.con].deref && ccopt.pic) || conht[mem.con].isfunc)
+                  r = (rex ? REL_GOTPCRELX_REX : REL_GOTPCRELX);
+               else
+                  r = REL_PCREL32;
+               objreloc(xcon2sym(mem.con), r, Stext, *pcode - objout.textbegin, disp);
+               I32(0);
+            }
          } else {
             /* var(,%reg,shift) */
             assert(!ccopt.pic && !ccopt.pie && "cannot encode [RIP-rel + REG] for position independent");
             B(/*mod 0*/ (reg & 7) << 3 | RSP);
             B(mem.cshift << 6 | ((mem.cindex & 7) << 3) | RBP); /* SIB [index*s + disp32] */
             objreloc(xcon2sym(mem.con), REL_ABS32S, Stext, *pcode - objout.textbegin, mem.disp);
+            I32(0);
          }
-         I32(0);
       } else {
          int mod;
          bool sib = 0;
@@ -427,13 +434,15 @@ encode(uchar **pcode, const struct desc *tab, int ntab, enum irclass k, struct o
       D(opc, nopc);
       assert(dst.t == OSYM);
       const char *sym = xcon2sym(dst.con);
-      if (sym != curfnsym) {
+      uint addr;
+      if (sym == curfnsym) {
+         I32(fnstart - *pcode - 4);
+      } else if (objhassym(sym, &addr) == Stext) {
+         I32(addr - (*pcode - objout.textbegin) - 4);
+      } else {
          enum relockind r = (ccopt.pie|ccopt.pic) ? REL_PLT32 : REL_PCREL32;
          objreloc(sym, r, Stext, *pcode - objout.textbegin, -4);
          I32(0);
-      } else {
-         /* self-recursive call */
-         I32(fnstart - *pcode - 4);
       }
       break;
    }
@@ -864,7 +873,8 @@ gencopy(uchar **pcode, enum irclass cls, struct block *blk, int curi, struct ope
       }
       /* normal (not 2-address) case */
    Lea:
-      if (isaddrcon(addr->base,0) && (ccopt.pic || conht[addr->base.i].isfunc)) {
+      if (isaddrcon(addr->base,0) && (ccopt.pic || conht[addr->base.i].isfunc)
+       && !objhassym(xcon2sym(addr->base.i), NULL)) {
          assert(!addr->disp && !addr->index.bits);
          val = addr->base;
          goto GOTLoad;
@@ -874,12 +884,15 @@ gencopy(uchar **pcode, enum irclass cls, struct block *blk, int curi, struct ope
       /* dst = 0 -> xor dst, dst; but only if it is ok to clobber flags */
       Xxor(pcode, kisint(cls) ? KI32 : cls, dst, dst);
    } else if (isaddrcon(val,0)) {
-      if (ccopt.pic || conht[val.i].isfunc) GOTLoad:
+      if ((ccopt.pic || conht[val.i].isfunc)
+       && !objhassym(xcon2sym(val.i), NULL)) {
+      GOTLoad:
          /* for  mov reg, [rip(sym@GOTPCREL)] */
          Xmov(pcode, cls, dst, mkoper(OSYM, .con = val.i, .cindex = NOINDEX));
-      else
+      } else {
          /* for  lea reg, [rip(sym)] */
          Xlea(pcode, cls, dst, mkoper(OSYM, .con = val.i, .cindex = NOINDEX));
+      }
    } else if (val.t == RXCON && in_range(concls(val), KI64, KPTR)) {
       /* movabs */
       assert(dst.t == OREG && in_range(dst.reg, RAX, R15));
-- 
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