From 658482d70f10962e44801565f059e26d85bf4746 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Sat, 22 Sep 2012 10:01:35 -0400
Subject: [PATCH] cmd/5g: fix register opt bug

The width was not being set on the address, which meant
that the optimizer could not find variables that overlapped
with it and mark them as having had their address taken.
This let to the compiler believing variables had been set
but never used and then optimizing away the set.

Fixes #4129.

R=ken2
CC=golang-dev
https://golang.org/cl/6552059
---
 src/cmd/5g/gsubr.c |  8 ++++++++
 src/cmd/5g/reg.c   | 37 ++++++++++++++++++++++++++++++++++---
 src/cmd/6g/reg.c   | 10 +++++++---
 src/cmd/8g/reg.c   |  7 +++++--
 4 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index 19036a36f7..8ad610a76f 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -1199,6 +1199,11 @@ naddr(Node *n, Addr *a, int canemitcode)
 	if(n == N)
 		return;
 
+	if(n->type != T && n->type->etype != TIDEAL) {
+		dowidth(n->type);
+		a->width = n->type->width;
+	}
+
 	switch(n->op) {
 	default:
 		fatal("naddr: bad %O %D", n->op, a);
@@ -1378,6 +1383,9 @@ naddr(Node *n, Addr *a, int canemitcode)
 			fatal("naddr: OADDR %d\n", a->type);
 		}
 	}
+	
+	if(a->width < 0)
+		fatal("naddr: bad width for %N -> %D", n, a);
 }
 
 /*
diff --git a/src/cmd/5g/reg.c b/src/cmd/5g/reg.c
index d130fc6ba2..c7fb2e02dd 100644
--- a/src/cmd/5g/reg.c
+++ b/src/cmd/5g/reg.c
@@ -416,10 +416,14 @@ regopt(Prog *firstp)
 				addrs.b[z] |= bit.b[z];
 		}
 
-//		print("bit=%2d addr=%d et=%-6E w=%-2d s=%S + %lld\n",
-//			i, v->addr, v->etype, v->width, v->sym, v->offset);
+		if(debug['R'] && debug['v'])
+			print("bit=%2d addr=%d et=%-6E w=%-2d s=%N + %lld\n",
+				i, v->addr, v->etype, v->width, v->node, v->offset);
 	}
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass1", firstr);
+
 	/*
 	 * pass 2
 	 * turn branch references to pointers
@@ -448,6 +452,9 @@ regopt(Prog *firstp)
 		print("	addr = %Q\n", addrs);
 	}
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass2", firstr);
+
 	/*
 	 * pass 2.5
 	 * find looping structure
@@ -457,6 +464,9 @@ regopt(Prog *firstp)
 	change = 0;
 	loopit(firstr, nr);
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass2.5", firstr);
+
 	/*
 	 * pass 3
 	 * iterate propagating usage
@@ -484,6 +494,9 @@ loop11:
 	if(change)
 		goto loop1;
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass3", firstr);
+
 
 	/*
 	 * pass 4
@@ -500,6 +513,9 @@ loop2:
 
 	addsplits();
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass4", firstr);
+
 	if(debug['R'] > 1) {
 		print("\nprop structure:\n");
 		for(r = firstr; r != R; r = r->link) {
@@ -551,6 +567,9 @@ loop2:
 		r->act.b[0] &= ~REGBITS;
 	}
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass4.5", firstr);
+
 	/*
 	 * pass 5
 	 * isolate regions
@@ -613,6 +632,9 @@ loop2:
 brk:
 	qsort(region, nregion, sizeof(region[0]), rcmp);
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass5", firstr);
+
 	/*
 	 * pass 6
 	 * determine used registers (paint2)
@@ -641,6 +663,10 @@ brk:
 			paint3(rgp->enter, rgp->varno, vreg, rgp->regno);
 		rgp++;
 	}
+
+	if(debug['R'] && debug['v'])
+		dumpit("pass6", firstr);
+
 	/*
 	 * pass 7
 	 * peep-hole on basic block
@@ -649,6 +675,9 @@ brk:
 		peep();
 	}
 
+	if(debug['R'] && debug['v'])
+		dumpit("pass7", firstr);
+
 	/*
 	 * last pass
 	 * eliminate nops
@@ -935,6 +964,8 @@ mkvar(Reg *r, Adr *a)
 	et = a->etype;
 	o = a->offset;
 	w = a->width;
+	if(w < 0)
+		fatal("bad width %d for %D", w, a);
 
 	for(i=0; i<nvar; i++) {
 		v = var+i;
@@ -1705,7 +1736,7 @@ fixjmp(Prog *firstp)
 	}
 	if(debug['R'] && debug['v'])
 		print("\n");
-
+	
 	// pass 2: mark all reachable code alive
 	mark(firstp);
 	
diff --git a/src/cmd/6g/reg.c b/src/cmd/6g/reg.c
index 21663c82fc..398e6a70d9 100644
--- a/src/cmd/6g/reg.c
+++ b/src/cmd/6g/reg.c
@@ -579,8 +579,9 @@ regopt(Prog *firstp)
 				addrs.b[z] |= bit.b[z];
 		}
 
-//		print("bit=%2d addr=%d et=%-6E w=%-2d s=%S + %lld\n",
-//			i, v->addr, v->etype, v->width, v->sym, v->offset);
+		if(debug['R'] && debug['v'])
+			print("bit=%2d addr=%d et=%-6E w=%-2d s=%N + %lld\n",
+				i, v->addr, v->etype, v->width, v->node, v->offset);
 	}
 
 	if(debug['R'] && debug['v'])
@@ -996,6 +997,8 @@ mkvar(Reg *r, Adr *a)
 	et = a->etype;
 	o = a->offset;
 	w = a->width;
+	if(w < 0)
+		fatal("bad width %d for %D", w, a);
 
 	flag = 0;
 	for(i=0; i<nvar; i++) {
@@ -1038,7 +1041,8 @@ mkvar(Reg *r, Adr *a)
 	v->node = node;
 
 	if(debug['R'])
-		print("bit=%2d et=%2E w=%d %#N %D\n", i, et, w, node, a);
+		print("bit=%2d et=%2d w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
+
 	ostats.nvar++;
 
 	bit = blsh(i);
diff --git a/src/cmd/8g/reg.c b/src/cmd/8g/reg.c
index 4ba9054ca9..bc80537cc3 100644
--- a/src/cmd/8g/reg.c
+++ b/src/cmd/8g/reg.c
@@ -474,8 +474,9 @@ regopt(Prog *firstp)
 				addrs.b[z] |= bit.b[z];
 		}
 
-//		print("bit=%2d addr=%d et=%-6E w=%-2d s=%S + %lld\n",
-//			i, v->addr, v->etype, v->width, v->sym, v->offset);
+		if(debug['R'] && debug['v'])
+			print("bit=%2d addr=%d et=%-6E w=%-2d s=%N + %lld\n",
+				i, v->addr, v->etype, v->width, v->node, v->offset);
 	}
 
 	if(debug['R'] && debug['v'])
@@ -864,6 +865,8 @@ mkvar(Reg *r, Adr *a)
 	et = a->etype;
 	o = a->offset;
 	w = a->width;
+	if(w < 0)
+		fatal("bad width %d for %D", w, a);
 
 	flag = 0;
 	for(i=0; i<nvar; i++) {
-- 
2.48.1