nir/loop_analyze: Don't test non-positive iterations count

Testing negative iterations count makes no sense, and can cause issues
when the unsigned type is used.
Testing 0 iterations is already covered with
will_break_on_first_iteration, so it can be skipped too.

Fixes: 6772a17a ("nir: Add a loop analysis pass")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9913
Signed-off-by: Sviatoslav Peleshko <sviatoslav.peleshko@globallogic.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26173>
(cherry picked from commit a6459e0f7bcb662130c79764ccf54ccfa9151182)

diff --git a/.pick_status.json b/.pick_status.json
index 446acdb..a10aa15 100644 (file)
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -204,7 +204,7 @@
         "description": "nir/loop_analyze: Don't test non-positive iterations count",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "6772a17acc8ee90f9398348251a4455f988208fd",
         "notes": null

diff --git a/src/compiler/nir/nir_loop_analyze.c b/src/compiler/nir/nir_loop_analyze.c
index f468d23..d9c0492 100644 (file)
--- a/src/compiler/nir/nir_loop_analyze.c
+++ b/src/compiler/nir/nir_loop_analyze.c
@@ -1138,11 +1138,13 @@ calculate_iterations(nir_def *basis, nir_def *limit_basis,
     */
    for (int bias = -1; bias <= 1; bias++) {
       const int iter_bias = iter_int + bias;
+      if (iter_bias < 1)
+         continue;
 
       if (test_iterations(iter_bias, step, limit, alu_op, bit_size,
                           induction_base_type, initial,
                           limit_rhs, invert_cond, execution_mode)) {
-         return iter_bias > 0 ? iter_bias - trip_offset : iter_bias;
+         return iter_bias - trip_offset;
       }
    }
 

diff --git a/src/compiler/nir/tests/loop_analyze_tests.cpp b/src/compiler/nir/tests/loop_analyze_tests.cpp
index f7c3c41..a530b7f 100644 (file)
--- a/src/compiler/nir/tests/loop_analyze_tests.cpp
+++ b/src/compiler/nir/tests/loop_analyze_tests.cpp
@@ -285,6 +285,7 @@ COMPARE_REVERSE(ishl)
 
 INOT_COMPARE(ilt_rev)
 INOT_COMPARE(ine)
+INOT_COMPARE(uge_rev)
 
 #define KNOWN_COUNT_TEST(_init_value, _cond_value, _incr_value, cond, incr, count) \
    TEST_F(nir_loop_analyze_test, incr ## _ ## cond ## _known_count_ ## count)    \
@@ -569,6 +570,16 @@ KNOWN_COUNT_TEST(0x0000000a, 0x00000005, 0xffffffff, inot_ilt_rev, iadd, 5)
 
 /*    uint i = 0;
  *    while (true) {
+ *       if (!(0 >= i))
+ *          break;
+ *
+ *       i += 1;
+ *    }
+ */
+KNOWN_COUNT_TEST(0x00000000, 0x00000000, 0x00000001, inot_uge_rev, iadd, 1)
+
+/*    uint i = 0;
+ *    while (true) {
  *       if (i != 0)
  *          break;
  *