Mesa (master): nvc0/ir: avoid infinite recursion when finding first uses of tex

[Ilia Mirkin]

Module: Mesa
Branch: master
Commit: c4bb436f7660c951cd27e52660cf825da68793e5
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=c4bb436f7660c951cd27e52660cf825da68793e5

Author: Ilia Mirkin <imirkin at alum.mit.edu>
Date:   Thu Aug 28 23:05:49 2014 -0400

nvc0/ir: avoid infinite recursion when finding first uses of tex

In certain circumstances, findFirstUses could end up doubling back on
instructions it had already processed, resulting in an infinite
recursion. Avoid this by keeping track of already-visited instructions.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83079
Tested-by: Tobias Klausmann <tobias.johannes.klausmann at mni.thm.de>
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
Cc: "10.2 10.3" <mesa-stable at lists.freedesktop.org>

---

 .../nouveau/codegen/nv50_ir_lowering_nvc0.cpp      |   32 +++++++++++++++-----
 .../nouveau/codegen/nv50_ir_lowering_nvc0.h        |    5 ++-
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
index 7da9b0b..92f9a15 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
@@ -174,15 +174,31 @@ NVC0LegalizePostRA::findOverwritingDefs(const Instruction *texi,
 }
 
 void
-NVC0LegalizePostRA::findFirstUses(const Instruction *texi,
-                                  const Instruction *insn,
-                                  std::list<TexUse> &uses)
+NVC0LegalizePostRA::findFirstUses(
+      const Instruction *texi,
+      const Instruction *insn,
+      std::list<TexUse> &uses,
+      std::tr1::unordered_set<const Instruction *>& visited)
 {
    for (int d = 0; insn->defExists(d); ++d) {
       Value *v = insn->getDef(d);
       for (Value::UseIterator u = v->uses.begin(); u != v->uses.end(); ++u) {
          Instruction *usei = (*u)->getInsn();
 
+         /* XXX HACK ALERT XXX
+          *
+          * This shouldn't have to be here, we should always be making forward
+          * progress by looking at the uses. However this somehow does not
+          * appear to be the case. Probably because this is being done right
+          * after RA, when the defs/uses lists have been messed with by node
+          * merging. This should probably be moved to being done right before
+          * RA. But this will do for now.
+          */
+         if (visited.find(usei) != visited.end())
+            continue;
+
+         visited.insert(usei);
+
          if (usei->op == OP_PHI || usei->op == OP_UNION) {
             // need a barrier before WAW cases
             for (int s = 0; usei->srcExists(s); ++s) {
@@ -197,11 +213,11 @@ NVC0LegalizePostRA::findFirstUses(const Instruction *texi,
              usei->op == OP_PHI ||
              usei->op == OP_UNION) {
             // these uses don't manifest in the machine code
-            findFirstUses(texi, usei, uses);
+            findFirstUses(texi, usei, uses, visited);
          } else
          if (usei->op == OP_MOV && usei->getDef(0)->equals(usei->getSrc(0)) &&
              usei->subOp != NV50_IR_SUBOP_MOV_FINAL) {
-            findFirstUses(texi, usei, uses);
+            findFirstUses(texi, usei, uses, visited);
          } else {
             addTexUse(uses, usei, insn);
          }
@@ -257,8 +273,10 @@ NVC0LegalizePostRA::insertTextureBarriers(Function *fn)
    uses = new std::list<TexUse>[texes.size()];
    if (!uses)
       return false;
-   for (size_t i = 0; i < texes.size(); ++i)
-      findFirstUses(texes[i], texes[i], uses[i]);
+   for (size_t i = 0; i < texes.size(); ++i) {
+      std::tr1::unordered_set<const Instruction *> visited;
+      findFirstUses(texes[i], texes[i], uses[i], visited);
+   }
 
    // determine the barrier level at each use
    for (size_t i = 0; i < texes.size(); ++i) {
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.h b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.h
index 7f39c28..d8ff5cd 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.h
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.h
@@ -20,6 +20,8 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#include <tr1/unordered_set>
+
 #include "codegen/nv50_ir.h"
 #include "codegen/nv50_ir_build_util.h"
 
@@ -69,7 +71,8 @@ private:
    bool insertTextureBarriers(Function *);
    inline bool insnDominatedBy(const Instruction *, const Instruction *) const;
    void findFirstUses(const Instruction *tex, const Instruction *def,
-                      std::list<TexUse>&);
+                      std::list<TexUse>&,
+                      std::tr1::unordered_set<const Instruction *>&);
    void findOverwritingDefs(const Instruction *tex, Instruction *insn,
                             const BasicBlock *term,
                             std::list<TexUse>&);