[Mesa-dev] [PATCH 17/20] nir: add helper to return inversion op of a comparision

[Timothy Arceri]

This will be used to help find the trip count of loops that look
like the following:

   while (a < x && i < 8) {
      ...
      i++;
   }

Where the NIR will end up looking something like this:

   vec1 32 ssa_0 = load_const (0x00000000 /* 0.000000 */)
   vec1 32 ssa_1 = load_const (0x00000008 /* 0.000000 */)
   loop {
      ...
      vec1 32 ssa_28 = ige ssa_26, ssa_3
      vec1 32 ssa_29 = ige ssa_27, ssa_1
      vec1 32 ssa_30 = iadd ssa_29, ssa_28
      vec1 ssa_31 = ieq ssa_30, ssa_0
      if ssa_31 {
         ...
         break
      } else {
         ...
      }
      ...
   }

So in order to find the trip count we need to find the inverse of
ige.
---
 src/compiler/nir/nir_loop_analyze.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/src/compiler/nir/nir_loop_analyze.c b/src/compiler/nir/nir_loop_analyze.c
index 5446e7a120..2dd7dd7b20 100644
--- a/src/compiler/nir/nir_loop_analyze.c
+++ b/src/compiler/nir/nir_loop_analyze.c
@@ -665,6 +665,35 @@ calculate_iterations(nir_const_value *initial, nir_const_value *step,
    return -1;
 }
 
+static nir_op
+inverse_comparision(nir_alu_instr *alu)
+{
+   switch (alu->op) {
+   case nir_op_fge:
+      return nir_op_flt;
+   case nir_op_ige:
+      return nir_op_ilt;
+   case nir_op_uge:
+      return nir_op_ult;
+   case nir_op_flt:
+      return nir_op_fge;
+   case nir_op_ilt:
+      return nir_op_ige;
+   case nir_op_ult:
+      return nir_op_uge;
+   case nir_op_feq:
+      return nir_op_fne;
+   case nir_op_ieq:
+      return nir_op_ine;
+   case nir_op_fne:
+      return nir_op_feq;
+   case nir_op_ine:
+      return nir_op_ieq;
+   default:
+      unreachable("Unsuported comparision!");
+   }
+}
+
 static bool
 is_supported_terminator_condition(nir_alu_instr *alu)
 {
-- 
2.19.2