From 9e36cbe4d8f8c9ff3d739ff9ead2a4a4988c0904 Mon Sep 17 00:00:00 2001
From: Roland Paterson-Jones <rolandpj@gmail.com>
Date: Tue, 19 Nov 2024 11:29:16 +0200
Subject: Combine fillrpo() and fillpreds() into fillcfg().

Remove edgedel() calls from fillrpo().

Call new prunephis() from fillpreds().
[Curiously this never seems to do anything even tho edgedel()
is no longer called from fillrpo()]

One remaining fillpreds() call in parse.c typecheck - seems
like it will still work the same.

defensive; fillcfg() combining fillrpo() and fillpreds() - problem after simpljmp() - think it is cos fillrpo() is still doing edgedel() which should now be covered by fillpreds()

comment out edgedel() in fillrpo() - fillcfg() no longer asserts after simpljmp() but seems like prunephis() never triggers???

static fillrpo(); remove edgedel() from fillrpo()

replace fillrpo() and/or fillpreds() with fillcfg()
---
 all.h  |  2 +-
 cfg.c  | 44 ++++++++++++++++++++++++++++++++++++++++----
 main.c | 12 +++++-------
 3 files changed, 46 insertions(+), 12 deletions(-)

diff --git a/all.h b/all.h
index fc98c52..a5a0163 100644
--- a/all.h
+++ b/all.h
@@ -527,7 +527,7 @@ void elimsb(Fn *);
 Blk *newblk(void);
 void edgedel(Blk *, Blk **);
 void fillpreds(Fn *);
-void fillrpo(Fn *);
+void fillcfg(Fn *);
 void filldom(Fn *);
 int sdom(Blk *, Blk *);
 int dom(Blk *, Blk *);
diff --git a/cfg.c b/cfg.c
index 631c356..99b6f40 100644
--- a/cfg.c
+++ b/cfg.c
@@ -11,6 +11,34 @@ newblk()
 	return b;
 }
 
+/* TODO - this never seems to do anything??? */
+static void
+prunephis(Fn *f)
+{
+	Blk *b;
+	Phi *p, **pp;
+	uint na, na0;
+
+	for (b = f->start; b; b = b->link) {
+		assert(b->id < f->nblk);
+		for (pp = &b->phi; (*pp);) {
+			p = *pp;
+			for (na = na0 = 0; na < p->narg; na++)
+				if (p->blk[na]->id != -1u) {
+					p->blk[na0] = p->blk[na];
+					p->arg[na0] = p->arg[na];
+					na0++;
+				}
+			if (na0 == 0) {
+				*pp = p->link;
+			} else {
+				p->narg = na0;
+				pp = &p->link;
+			}
+		}
+	}
+}
+
 void
 edgedel(Blk *bs, Blk **pbd)
 {
@@ -53,7 +81,7 @@ addpred(Blk *bp, Blk *bc)
 	bc->pred[bc->npred-1] = bp;
 }
 
-/* fill predecessors information in blocks */
+/* fill predecessors information in blocks; prune dead phi refs */
 void
 fillpreds(Fn *f)
 {
@@ -67,6 +95,8 @@ fillpreds(Fn *f)
 		if (b->s2 && b->s2 != b->s1)
 			addpred(b, b->s2);
 	}
+	/* TODO - this never seems to do anything??? */
+	prunephis(f);
 }
 
 static void
@@ -89,7 +119,7 @@ porec(Blk *b, uint *npo)
 }
 
 /* fill the rpo information; prune dead blks */
-void
+static void
 fillrpo(Fn *f)
 {
 	Blk *b, **p;
@@ -104,8 +134,6 @@ fillrpo(Fn *f)
 		f->rpo = vnew(f->nblk, sizeof f->rpo[0], PFn);
 	for (p=&f->start; (b=*p);) {
 		if (b->id == -1u) {
-			edgedel(b, &b->s1);
-			edgedel(b, &b->s2);
 			*p = b->link;
 		} else {
 			b->id = f->nblk-b->id-1; /* po -> rpo */
@@ -115,6 +143,14 @@ fillrpo(Fn *f)
 	}
 }
 
+/* fill rpo, preds; prune dead blks, prune dead blk refs from phis */
+void
+fillcfg(Fn *f)
+{
+	fillrpo(f);
+	fillpreds(f);
+}
+
 /* for dominators computation, read
  * "A Simple, Fast Dominance Algorithm"
  * by K. Cooper, T. Harvey, and K. Kennedy.
diff --git a/main.c b/main.c
index 5ecb4d0..977c55b 100644
--- a/main.c
+++ b/main.c
@@ -59,8 +59,7 @@ func(Fn *fn)
 		printfn(fn, stderr);
 	}
 	T.abi0(fn);
-	fillrpo(fn);
-	fillpreds(fn);
+	fillcfg(fn);
 	filluse(fn);
 	promote(fn);
 	filluse(fn);
@@ -79,19 +78,18 @@ func(Fn *fn)
 	fold(fn);
 	T.abi1(fn);
 	simpl(fn);
-	fillpreds(fn);
+	fillcfg(fn);
 	filluse(fn);
 	T.isel(fn);
-	fillrpo(fn);
+	fillcfg(fn);
 	filllive(fn);
 	fillloop(fn);
 	fillcost(fn);
 	spill(fn);
 	rega(fn);
-	fillrpo(fn);
+	fillcfg(fn);
 	simpljmp(fn);
-	fillpreds(fn);
-	fillrpo(fn);
+	fillcfg(fn);
 	assert(fn->rpo[0] == fn->start);
 	for (n=0;; n++)
 		if (n == fn->nblk-1) {
-- 
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