r600/sb: Fix loop optimization related hangs on eg

Make sure unused ops and their references are removed, prior to entering
the GCM (global code motion) pass, to stop GCM from breaking the loop
logic and thus hanging the GPU.

Turns out, that sb has problems with loops and node optimizations
regarding associative folding:

- the global code motion (gcm) pass moves ops up a loop level/basic block
until they've fulfilled their total usage count
- if there are ops folded into others, the usage count won't be
fulfilled and thus the op moved way up to the top
- within GCM the op would be visited and their deps would be moved
alongside it, to fulfill the src constaints
- in a loop, an unused op is moved out of the loop and GCM would move
the src value ops up as well
- now here arises the problem: if the loop counter is one of the src
values it would get moved up as well, the loop break condition would
never get hit and the shader turn into an endless loop, resulting in the
GPU hanging and being reset

A reduced (albeit nonsense) piglit example would be:

[require]
GLSL >= 1.20

[fragment shader]

uniform int SIZE;
uniform vec4 lights[512];

void main()
{
    float x = 0;
    for(int i = 0; i < SIZE; i++)
        x += lights[2*i+1].x;
}

[test]
uniform int SIZE 1
draw rect -1 -1 2 2

Which gets optimized to:

===== SHADER #12 OPT ================================== PS/BARTS/EVERGREEN =====
===== 42 dw ===== 1 gprs ===== 2 stack =========================================
ALU 3 @24
     1      y: MOV                R0.y,  0
            t: MULLO_UINT         R0.w,  [0x00000002 2.8026e-45].x, R0.z

LOOP_START_DX10 @22
PUSH @6
ALU 1 @30 KC0[CB0:0-15]
     2 M    x: PRED_SETGE_INT     __.x,  R0.z, KC0[0].x
JUMP @14 POP:1
LOOP_BREAK @20
POP @14 POP:1
ALU 2 @32
     3      x: ADD_INT            R0.x,  R0.w, [0x00000002 2.8026e-45].x

TEX 1 @36
               VFETCH             R0.x___, R0.x,   RID:0   MFC:16 UCF:0 FMT[..]
ALU 1 @40
     4      y: ADD                R0.y,  R0.y, R0.x
LOOP_END @4
EXPORT_DONE        PIXEL 0     R0.____  EOP
===== SHADER_END ===============================================================

Notice R0.z being the loop counter/break condition relevant register
and being never incremented at all. Also some of the loop content
has been moved out of it, to fulfill the requirements for the one unused
op.

With a debug build of mesa this would produce an error like
error at : PRED_SETGE_INT     __, __, EM.2,    R1.x.2||[email protected], C0.x
  : operand value R1.x.2||[email protected] was not previously written to its gpr
and the compilation would fail due to this. On a release build it gets
passed to the GPU.

When using this patch, the loop remains intact:

===== SHADER #12 OPT ================================== PS/BARTS/EVERGREEN =====
===== 48 dw ===== 1 gprs ===== 2 stack =========================================
ALU 2 @24
     1      y: MOV                R0.y,  0
            z: MOV                R0.z,  0
LOOP_START_DX10 @22
PUSH @6
ALU 1 @28 KC0[CB0:0-15]
     2 M    x: PRED_SETGE_INT     __.x,  R0.z, KC0[0].x
JUMP @14 POP:1
LOOP_BREAK @20
POP @14 POP:1
ALU 4 @30
     3      t: MULLO_UINT         T0.x,  [0x00000002 2.8026e-45].x, R0.z

     4      x: ADD_INT            R0.x,  T0.x, [0x00000002 2.8026e-45].x

TEX 1 @40
               VFETCH             R0.x___, R0.x,   RID:0   MFC:16 UCF:0 FMT[..]
ALU 2 @44
     5      y: ADD                R0.y,  R0.y, R0.x
            z: ADD_INT            R0.z,  R0.z, 1
LOOP_END @4
EXPORT_DONE        PIXEL 0     R0.____  EOP
===== SHADER_END ===============================================================

Piglit: ./piglit summary console -d results/*_gpu_noglx
        name: unpatched_gpu_noglx patched_gpu_noglx
        ----  ------------------- -----------------
        pass:               18016             18021
        fail:                 748               743
        crash:                  7                 7
        skip:                1124              1124
        timeout:                0                 0
        warn:                  13                13
        incomplete:             0                 0
        dmesg-warn:             0                 0
        dmesg-fail:             0                 0
        changes:                0                 5
        fixes:                  0                 5
        regressions:            0                 0
        total:              19908             19908

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94900
Tested-by: Heiko Przybyl <[email protected]>
Tested-on: Barts PRO HD6850
Signed-off-by: Heiko Przybyl <[email protected]>
Signed-off-by: Marek Olšák <[email protected]>
(cherry picked from commit e933246013eef376804662f3fcf4646c143c6c88)
Nominated-by: Andreas Boll <[email protected]>

6 files changed, 68 insertions, 30 deletions

diff --git a/src/gallium/drivers/r600/sb/sb_dce_cleanup.cpp b/src/gallium/drivers/r600/sb/sb_dce_cleanup.cpp
index 79aef9106a4..abae2bf69d7 100644
--- a/src/gallium/drivers/r600/sb/sb_dce_cleanup.cpp
+++ b/src/gallium/drivers/r600/sb/sb_dce_cleanup.cpp
@@ -30,6 +30,18 @@
 
 namespace r600_sb {
 
+int dce_cleanup::run() {
+	int r;
+
+	// Run cleanup for as long as there are unused nodes.
+	do {
+		nodes_changed = false;
+		r = vpass::run();
+	} while (r == 0 && nodes_changed);
+
+	return r;
+}
+
 bool dce_cleanup::visit(node& n, bool enter) {
 	if (enter) {
 	} else {
@@ -110,7 +122,18 @@ bool dce_cleanup::visit(region_node& n, bool enter) {
 void dce_cleanup::cleanup_dst(node& n) {
 	if (!cleanup_dst_vec(n.dst) && remove_unused &&
 			!n.dst.empty() && !(n.flags & NF_DONT_KILL) && n.parent)
+	{
+		// Delete use references to the removed node from the src values.
+		for (vvec::iterator I = n.src.begin(), E = n.src.end(); I != E; ++I) {
+			value* v = *I;
+			if (v && v->def && v->uses.size())
+			{
+				v->remove_use(&n);
+			}
+		}
 		n.remove();
+		nodes_changed = true;
+	}
 }
 
 bool dce_cleanup::visit(container_node& n, bool enter) {
@@ -130,7 +153,7 @@ bool dce_cleanup::cleanup_dst_vec(vvec& vv) {
 		if (v->gvn_source && v->gvn_source->is_dead())
 			v->gvn_source = NULL;
 
-		if (v->is_dead() || (remove_unused && !v->is_rel() && !v->uses))
+		if (v->is_dead() || (remove_unused && !v->is_rel() && !v->uses.size()))
 			v = NULL;
 		else
 			alive = true;
diff --git a/src/gallium/drivers/r600/sb/sb_gcm.cpp b/src/gallium/drivers/r600/sb/sb_gcm.cpp
index 236b2ea0031..9c75389ada0 100644
--- a/src/gallium/drivers/r600/sb/sb_gcm.cpp
+++ b/src/gallium/drivers/r600/sb/sb_gcm.cpp
@@ -199,10 +199,9 @@ void gcm::td_release_val(value *v) {
 		sblog << "\n";
 	);
 
-	use_info *u = v->uses;
-	while (u) {
+	for (uselist::iterator I = v->uses.begin(), E = v->uses.end(); I != E; ++I) {
+		use_info *u = *I;
 		if (u->op->parent != &pending) {
-			u = u->next;
 			continue;
 		}
 
@@ -212,6 +211,7 @@ void gcm::td_release_val(value *v) {
 			sblog << "\n";
 		);
 
+		assert(uses[u->op] > 0);
 		if (--uses[u->op] == 0) {
 			GCM_DUMP(
 				sblog << "td        released : ";
@@ -222,7 +222,6 @@ void gcm::td_release_val(value *v) {
 			pending.remove_node(u->op);
 			ready.push_back(u->op);
 		}
-		u = u->next;
 	}
 
 }
diff --git a/src/gallium/drivers/r600/sb/sb_ir.cpp b/src/gallium/drivers/r600/sb/sb_ir.cpp
index 5226893de75..d989dce62c9 100644
--- a/src/gallium/drivers/r600/sb/sb_ir.cpp
+++ b/src/gallium/drivers/r600/sb/sb_ir.cpp
@@ -255,7 +255,7 @@ void container_node::expand() {
 void node::remove() {parent->remove_node(this);
 }
 
-value_hash node::hash_src() {
+value_hash node::hash_src() const {
 
 	value_hash h = 12345;
 
@@ -269,7 +269,7 @@ value_hash node::hash_src() {
 }
 
 
-value_hash node::hash() {
+value_hash node::hash() const {
 
 	if (parent && parent->subtype == NST_LOOP_PHI_CONTAINER)
 		return 47451;
diff --git a/src/gallium/drivers/r600/sb/sb_ir.h b/src/gallium/drivers/r600/sb/sb_ir.h
index 4fc4da2fb21..74c0549a813 100644
--- a/src/gallium/drivers/r600/sb/sb_ir.h
+++ b/src/gallium/drivers/r600/sb/sb_ir.h
@@ -446,15 +446,16 @@ enum use_kind {
 };
 
 struct use_info {
-	use_info *next;
 	node *op;
 	use_kind kind;
 	int arg;
 
-	use_info(node *n, use_kind kind, int arg, use_info* next)
-		: next(next), op(n), kind(kind), arg(arg) {}
+	use_info(node *n, use_kind kind, int arg)
+		: op(n), kind(kind), arg(arg) {}
 };
 
+typedef std::list< use_info * > uselist;
+
 enum constraint_kind {
 	CK_SAME_REG,
 	CK_PACKED_BS,
@@ -498,7 +499,7 @@ public:
 	value_hash ghash;
 
 	node *def, *adef;
-	use_info *uses;
+	uselist uses;
 
 	ra_constraint *constraint;
 	ra_chunk *chunk;
@@ -585,6 +586,7 @@ public:
 	}
 
 	void add_use(node *n, use_kind kind, int arg);
+	void remove_use(const node *n);
 
 	value_hash hash();
 	value_hash rel_hash();
@@ -790,8 +792,8 @@ public:
 	void replace_with(node *n);
 	void remove();
 
-	virtual value_hash hash();
-	value_hash hash_src();
+	virtual value_hash hash() const;
+	value_hash hash_src() const;
 
 	virtual bool fold_dispatch(expr_handler *ex);
 
diff --git a/src/gallium/drivers/r600/sb/sb_pass.h b/src/gallium/drivers/r600/sb/sb_pass.h
index 0346df1b167..e878f8c70ca 100644
--- a/src/gallium/drivers/r600/sb/sb_pass.h
+++ b/src/gallium/drivers/r600/sb/sb_pass.h
@@ -124,7 +124,9 @@ class dce_cleanup : public vpass {
 public:
 
 	dce_cleanup(shader &s) : vpass(s),
-		remove_unused(s.dce_flags & DF_REMOVE_UNUSED) {}
+		remove_unused(s.dce_flags & DF_REMOVE_UNUSED), nodes_changed(false) {}
+
+	virtual int run();
 
 	virtual bool visit(node &n, bool enter);
 	virtual bool visit(alu_group_node &n, bool enter);
@@ -140,6 +142,8 @@ private:
 	void cleanup_dst(node &n);
 	bool cleanup_dst_vec(vvec &vv);
 
+	// Did we alter/remove nodes during a single pass?
+	bool nodes_changed;
 };
 
 
diff --git a/src/gallium/drivers/r600/sb/sb_valtable.cpp b/src/gallium/drivers/r600/sb/sb_valtable.cpp
index eb242b1c26f..a8b7b49cd41 100644
--- a/src/gallium/drivers/r600/sb/sb_valtable.cpp
+++ b/src/gallium/drivers/r600/sb/sb_valtable.cpp
@@ -220,17 +220,33 @@ void value::add_use(node* n, use_kind kind, int arg) {
 	dump::dump_op(n);
 	sblog << "     kind " << kind << "    arg " << arg << "\n";
 	}
-	uses = new use_info(n, kind, arg, uses);
+	uses.push_back(new use_info(n, kind, arg));
 }
 
-unsigned value::use_count() {
-	use_info *u = uses;
-	unsigned c = 0;
-	while (u) {
-		++c;
-		u = u->next;
+struct use_node_comp {
+	explicit use_node_comp(const node *n) : n(n) {}
+	bool operator() (const use_info *u) {
+		return u->op->hash() == n->hash();
+	}
+
+	private:
+		const node *n;
+};
+
+void value::remove_use(const node *n) {
+	uselist::iterator it =
+		std::find_if(uses.begin(), uses.end(), use_node_comp(n));
+
+	if (it != uses.end())
+	{
+		// TODO assert((*it)->kind == kind) ?
+		// TODO assert((*it)->arg == arg) ?
+		uses.erase(it);
 	}
-	return c;
+}
+
+unsigned value::use_count() {
+	return uses.size();
 }
 
 bool value::is_global() {
@@ -274,13 +290,7 @@ bool value::is_prealloc() {
 }
 
 void value::delete_uses() {
-	use_info *u, *c = uses;
-	while (c) {
-		u = c->next;
-		delete c;
-		c = u;
-	}
-	uses = NULL;
+	uses.erase(uses.begin(), uses.end());
 }
 
 void ra_constraint::update_values() {
@@ -468,7 +478,7 @@ bool r600_sb::sb_value_set::add_vec(vvec& vv) {
 bool r600_sb::sb_value_set::contains(value* v) {
 	unsigned b = v->uid - 1;
 	if (b < bs.size())
-		return bs.get(v->uid - 1);
+		return bs.get(b);
 	else
 		return false;
 }