From 7cd143c0c42779778eec755d4386ea752fb5f1f4 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Fri, 21 Jun 2013 15:06:31 +0200
Subject: [PATCH] piggy-back the next shift directly onto the reduce
---
src/backends/lr.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/src/backends/lr.c b/src/backends/lr.c
index 2f7d5e48..03264b5c 100644
--- a/src/backends/lr.c
+++ b/src/backends/lr.c
@@ -268,12 +268,7 @@ bool h_lrengine_step(HLREngine *engine, const HLRAction *action)
assert(action->type == HLR_SHIFT || action->type == HLR_REDUCE);
- if(action->type == HLR_SHIFT) {
- h_slist_push(left, (void *)(uintptr_t)engine->state);
- h_slist_drop(right); // symbol (discard)
- h_slist_push(left, h_slist_drop(right)); // semantic value
- engine->state = action->nextstate;
- } else {
+ if(action->type == HLR_REDUCE) {
assert(action->type == HLR_REDUCE);
size_t len = action->production.length;
HCFChoice *symbol = action->production.lhs;
@@ -318,8 +313,18 @@ bool h_lrengine_step(HLREngine *engine, const HLRAction *action)
// this is LR, building a right-most derivation bottom-up, so no reduce can
// follow a reduce. we can also assume no conflict follows for GLR if we
// use LALR tables, because only terminal symbols (lookahead) get reduces.
- const HLRAction *next = h_lr_lookup(engine->table, engine->state, symbol);
- assert(next == NULL || next->type == HLR_SHIFT);
+ action = h_lr_lookup(engine->table, engine->state, symbol);
+ if(action == NULL)
+ return false; // no handle after reduce; terminate
+ assert(action->type == HLR_SHIFT);
+ }
+
+ // this could be the original action, or a shift piggy-backed onto reduce
+ if(action->type == HLR_SHIFT) {
+ h_slist_push(left, (void *)(uintptr_t)engine->state);
+ h_slist_drop(right); // symbol (discard)
+ h_slist_push(left, h_slist_drop(right)); // semantic value
+ engine->state = action->nextstate;
}
return true;
--
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