From cf9548efe2770e1597c49903f065572aaad96fd6 Mon Sep 17 00:00:00 2001
From: Nils Goroll <nils.goroll@uplex.de>
Date: Sat, 10 Apr 2021 14:18:22 +0200
Subject: [PATCH] vcc: Track the built-in subs which static calls originate
 from

We use another "method" bitmask to record the built-in subs from which
static calls originate.

This allows us to indentify those subs which are called from
housekeeping only, allowing us to selectively disable compiler
optimizations.

VGC diff for the example from
https://github.com/varnishcache/varnish-cache/issues/3545#issue-824634168

```diff
@@ -2242,7 +2278,7 @@

 #define END_ if (*ctx->handling) return

-void v_matchproto_(vcl_func_f)
+void v_dont_optimize v_matchproto_(vcl_func_f)
 VGC_function_a(VRT_CTX, enum vcl_func_call_e call,
     enum vcl_func_fail_e *failp)
 {
```

Fixes #3545
---
 lib/libvcc/vcc_compile.c | 5 ++++-
 lib/libvcc/vcc_compile.h | 1 +
 lib/libvcc/vcc_xref.c    | 7 +++++--
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/libvcc/vcc_compile.c b/lib/libvcc/vcc_compile.c
index 9065679779..88c8baf5b8 100644
--- a/lib/libvcc/vcc_compile.c
+++ b/lib/libvcc/vcc_compile.c
@@ -191,7 +191,9 @@ vcc_EmitProc(struct vcc *tl, struct proc *p)
 		maskcmp = "&";
 	}
 
-	if ((mask & VCL_MET_TASK_H) && (mask & ~VCL_MET_TASK_H) == 0)
+	if (dyn == 0 &&
+	    (p->calledfrom &  VCL_MET_TASK_H) != 0 &&
+	    (p->calledfrom & ~VCL_MET_TASK_H) == 0)
 		cc_adv = "v_dont_optimize ";
 	else
 		cc_adv = "";
@@ -210,6 +212,7 @@ vcc_EmitProc(struct vcc *tl, struct proc *p)
 	Fh(tl, 1, "\t.n\t\t= %d,\n", nsub);
 	Fh(tl, 1, "\t.nref\t\t= %d,\n", p->sym->nref);
 	Fh(tl, 1, "\t.called\t\t= %d\n", p->called);
+	Fh(tl, 1, "\t// calledfrom\t  0x%x\n", p->calledfrom);
 	Fh(tl, 1, "}};\n");
 
 	if (dyn) {
diff --git a/lib/libvcc/vcc_compile.h b/lib/libvcc/vcc_compile.h
index b52c532163..1ec423b303 100644
--- a/lib/libvcc/vcc_compile.h
+++ b/lib/libvcc/vcc_compile.h
@@ -213,6 +213,7 @@ struct proc {
 	unsigned		called;
 	unsigned		active;
 	unsigned		okmask;
+	unsigned		calledfrom;
 	struct token		*return_tok[VCL_RET_MAX];
 	struct vsb		*cname;
 	struct vsb		*prologue;
diff --git a/lib/libvcc/vcc_xref.c b/lib/libvcc/vcc_xref.c
index e3351ec48e..433f5e7b82 100644
--- a/lib/libvcc/vcc_xref.c
+++ b/lib/libvcc/vcc_xref.c
@@ -207,6 +207,7 @@ vcc_CheckActionRecurse(struct vcc *tl, struct proc *p, unsigned bitmap)
 			vcc_ErrWhere(tl, pc->t);
 			return (1);
 		}
+		pc->sym->proc->calledfrom |= p->calledfrom;
 		pc->sym->proc->called++;
 		pc->sym->nref += u;
 		if (vcc_CheckActionRecurse(tl, pc->sym->proc, bitmap)) {
@@ -233,10 +234,12 @@ vcc_checkaction(struct vcc *tl, const struct symbol *sym)
 	AN(p);
 	AN(p->name);
 
-	if (p->method == NULL)
+	if (p->method == NULL) {
 		bitmap = ~0U;
-	else
+	} else {
 		bitmap = p->method->ret_bitmap;
+		p->calledfrom = p->method->bitval;
+	}
 
 	if (! vcc_CheckActionRecurse(tl, p, bitmap))
 		return;