[Mesa-dev] [PATCH 21/30] i965/fs: Add live interval validation pass.

[Francisco Jerez]

This could be improved somewhat with additional validation of the
calculated live in/out sets and by checking that the calculated live
intervals are minimal (which isn't strictly necessary to guarantee the
correctness of the program).  This should be good enough though to
catch accidental use of stale liveness results due to missing or
incorrect analysis invalidation.
---
 .../drivers/dri/i965/brw_fs_live_variables.cpp     | 41 ++++++++++++++++++++++
 src/mesa/drivers/dri/i965/brw_fs_live_variables.h  |  3 ++
 2 files changed, 44 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp b/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
index 4b0943f..215349a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp
@@ -304,6 +304,47 @@ fs_live_variables::~fs_live_variables()
    ralloc_free(mem_ctx);
 }
 
+static bool
+check_register_live_range(const fs_live_variables *live, int ip,
+                          const fs_reg &reg, unsigned n)
+{
+   const unsigned var = live->var_from_reg(reg);
+
+   if (var + n > unsigned(live->num_vars) ||
+       live->vgrf_start[reg.nr] > ip || live->vgrf_end[reg.nr] < ip)
+      return false;
+
+   for (unsigned j = 0; j < n; j++) {
+      if (live->start[var + j] > ip || live->end[var + j] < ip)
+         return false;
+   }
+
+   return true;
+}
+
+bool
+fs_live_variables::validate(const backend_shader *s) const
+{
+   int ip = 0;
+
+   foreach_block_and_inst(block, fs_inst, inst, s->cfg) {
+      for (unsigned i = 0; i < inst->sources; i++) {
+         if (inst->src[i].file == VGRF &&
+             !check_register_live_range(this, ip,
+                                        inst->src[i], inst->regs_read(i)))
+            return false;
+      }
+
+      if (inst->dst.file == VGRF &&
+         !check_register_live_range(this, ip, inst->dst, inst->regs_written))
+         return false;
+
+      ip++;
+   }
+
+   return true;
+}
+
 void
 fs_visitor::invalidate_live_intervals()
 {
diff --git a/src/mesa/drivers/dri/i965/brw_fs_live_variables.h b/src/mesa/drivers/dri/i965/brw_fs_live_variables.h
index e1cd12c..c2a3c63 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_live_variables.h
+++ b/src/mesa/drivers/dri/i965/brw_fs_live_variables.h
@@ -69,6 +69,9 @@ public:
    fs_live_variables(const backend_shader *s);
    ~fs_live_variables();
 
+   bool
+   validate(const backend_shader *s) const;
+
    bool vars_interfere(int a, int b) const;
    bool vgrfs_interfere(int a, int b) const;
    int var_from_reg(const fs_reg &reg) const
-- 
2.7.0