Mesa (master): st/glsl_to_tgsi: reduce stack explosion in recursive expression visitor

[Nicolai Hähnle]

Module: Mesa
Branch: master
Commit: 98c348d26b28a662d093543ecb7ca839e7883e8e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=98c348d26b28a662d093543ecb7ca839e7883e8e

Author: Nicolai Hähnle <nicolai.haehnle at amd.com>
Date:   Mon Apr 25 18:20:50 2016 -0500

st/glsl_to_tgsi: reduce stack explosion in recursive expression visitor

In optimized builds, visit(ir_expression *) experiences inlining with gcc that
leads the function to have a roughly 32KB stack frame. This is a problem given
that the function is called recursively. In non-optimized builds, the stack
frame is much smaller, hence one gets crashes that happen only in optimized
builds.

Arguably there is a compiler bug or at least severe misfeature here. In any
case, the easy thing to do for now seems to be moving the bulk of the
non-recursive code into a separate function. This is sufficient to convince my
version of gcc not to blow up the stack frame of the recursive part. Just to be
sure, add the gcc-specific noinline attribute to prevent this bug from
reoccuring if inliner heuristics change.

v2: put ATTRIBUTE_NOINLINE into macros.h

Cc: "11.1 11.2" <mesa-stable at lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95133
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95026
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92850
Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>
Reviewed-by: Rob Clark <robdclark at gmail.com>

---

 src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 20 ++++++++++++++++----
 src/util/macros.h                          |  6 ++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index ad818a8..3c4c91b 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -450,6 +450,8 @@ public:
    virtual void visit(ir_barrier *);
    /*@}*/
 
+   void visit_expression(ir_expression *, st_src_reg *) ATTRIBUTE_NOINLINE;
+
    void visit_atomic_counter_intrinsic(ir_call *);
    void visit_ssbo_intrinsic(ir_call *);
    void visit_membar_intrinsic(ir_call *);
@@ -1535,10 +1537,7 @@ glsl_to_tgsi_visitor::reladdr_to_temp(ir_instruction *ir,
 void
 glsl_to_tgsi_visitor::visit(ir_expression *ir)
 {
-   unsigned int operand;
    st_src_reg op[ARRAY_SIZE(ir->operands)];
-   st_src_reg result_src;
-   st_dst_reg result_dst;
 
    /* Quick peephole: Emit MAD(a, b, c) instead of ADD(MUL(a, b), c)
     */
@@ -1561,7 +1560,7 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
    if (ir->operation == ir_quadop_vector)
       assert(!"ir_quadop_vector should have been lowered");
 
-   for (operand = 0; operand < ir->get_num_operands(); operand++) {
+   for (unsigned int operand = 0; operand < ir->get_num_operands(); operand++) {
       this->result.file = PROGRAM_UNDEFINED;
       ir->operands[operand]->accept(this);
       if (this->result.file == PROGRAM_UNDEFINED) {
@@ -1578,6 +1577,19 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
       assert(!ir->operands[operand]->type->is_matrix());
    }
 
+   visit_expression(ir, op);
+}
+
+/* The non-recursive part of the expression visitor lives in a separate
+ * function and should be prevented from being inlined, to avoid a stack
+ * explosion when deeply nested expressions are visited.
+ */
+void
+glsl_to_tgsi_visitor::visit_expression(ir_expression* ir, st_src_reg *op)
+{
+   st_src_reg result_src;
+   st_dst_reg result_dst;
+
    int vector_elements = ir->operands[0]->type->vector_elements;
    if (ir->operands[1]) {
       vector_elements = MAX2(vector_elements,
diff --git a/src/util/macros.h b/src/util/macros.h
index 773e12f..c0bfb15 100644
--- a/src/util/macros.h
+++ b/src/util/macros.h
@@ -214,6 +214,12 @@ do {                       \
 #define MUST_CHECK
 #endif
 
+#if defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590))
+#define ATTRIBUTE_NOINLINE __attribute__((noinline))
+#else
+#define ATTRIBUTE_NOINLINE
+#endif
+
 /** Compute ceiling of integer quotient of A divided by B. */
 #define DIV_ROUND_UP( A, B )  ( (A) % (B) == 0 ? (A)/(B) : (A)/(B)+1 )