From 0848894878ef90b1c6d81e4a6e2741508d0b99f5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 18 Aug 2017 08:27:51 +0200
Subject: Pack instructions using 'q', 'c', and 's'

Update the pack engine to safely push literal operands to the pack
stack and to safely pop them back to another code address. That
will allow packing of more instructions.
---
 erts/emulator/beam/beam_load.c | 39 +++++++++++++++++++++++++++++++--------
 1 file changed, 31 insertions(+), 8 deletions(-)

(limited to 'erts/emulator/beam/beam_load.c')

diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 98701db558..982f998ae3 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -2495,16 +2495,32 @@ load_code(LoaderState* stp)
 	 * The packing engine.
 	 */
 	if (opc[stp->specific_op].pack[0]) {
-	    char* prog;		/* Program for packing engine. */
-	    BeamInstr stack[8];	/* Stack. */
-	    BeamInstr* sp = stack;	/* Points to next free position. */
-	    BeamInstr packed = 0;	/* Accumulator for packed operations. */
+	    char* prog;            /* Program for packing engine. */
+	    struct pack_stack {
+                BeamInstr instr;
+                LiteralPatch* patch;
+            } stack[8];            /* Stack. */
+	    struct pack_stack* sp = stack; /* Points to next free position. */
+	    BeamInstr packed = 0; /* Accumulator for packed operations. */
 
 	    for (prog = opc[stp->specific_op].pack; *prog; prog++) {
 		switch (*prog) {
 		case 'g':	/* Get instruction; push on stack. */
-		    *sp++ = code[--ci];
-		    break;
+                    {
+                        LiteralPatch* lp;
+
+                        ci--;
+                        sp->instr = code[ci];
+                        sp->patch = 0;
+                        for (lp = stp->literal_patches; lp && lp->pos > ci-MAX_OPARGS; lp = lp->next) {
+                            if (lp->pos == ci) {
+                                sp->patch = lp;
+                                break;
+                            }
+                        }
+                        sp++;
+                    }
+                    break;
 		case 'i':	/* Initialize packing accumulator. */
 		    packed = code[--ci];
 		    break;
@@ -2520,10 +2536,17 @@ load_code(LoaderState* stp)
 		    break;
 #endif
 		case 'p':	/* Put instruction (from stack). */
-		    code[ci++] = *--sp;
+                    --sp;
+                    code[ci] = sp->instr;
+                    if (sp->patch) {
+                        sp->patch->pos = ci;
+                    }
+                    ci++;
 		    break;
 		case 'P':	/* Put packed operands. */
-		    *sp++ = packed;
+                    sp->instr = packed;
+                    sp->patch = 0;
+                    sp++;
 		    packed = 0;
 		    break;
 		default:
-- 
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