glsl: fix infinite loop caused by bug in loop unrolling pass

Just checking for 2 jumps is not enough to be sure we can do a
complex loop unroll. We need to make sure we also have also found
2 loop terminators.

Without this we were attempting to unroll a loop where the second
jump was nested inside multiple ifs which loop analysis is unable
to detect as a terminator. We ended up splicing out the first
terminator but failed to actually unroll the loop, this resulted
in the creation of a possible infinite loop.

Fixes: 646621c66da9 "glsl: make loop unrolling more like the nir unrolling path"

Tested-by: Gert Wollny <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105670
(cherry picked from commit 56b867395dee1a48594b27987d3bf68a4e745dda)

Squashed with:

glsl: remove unreachable assert()

Earlier commit enforced that we'll bail out if the number of terminators
is different than 2. With that in mind, the assert() will never trigger.

Fixes: 56b867395de ("glsl: fix infinite loop caused by bug in loop
unrolling pass")
Reviewed-by: Timothy Arceri <[email protected]>
Signed-off-by: Emil Velikov <[email protected]>
(cherry picked from commit 8eceac9de7d3cd4fddabbe61d512acfed9812169)

1 files changed, 1 insertions, 3 deletions

diff --git a/src/compiler/glsl/loop_unroll.cpp b/src/compiler/glsl/loop_unroll.cpp
index 6e06a30fb91..874f4185681 100644
--- a/src/compiler/glsl/loop_unroll.cpp
+++ b/src/compiler/glsl/loop_unroll.cpp
@@ -519,7 +519,7 @@ loop_unroll_visitor::visit_leave(ir_loop *ir)
     * isn't any additional unknown terminators, or any other jumps nested
     * inside futher ifs.
     */
-   if (ls->num_loop_jumps != 2)
+   if (ls->num_loop_jumps != 2 || ls->terminators.length() != 2)
       return visit_continue;
 
    ir_instruction *first_ir =
@@ -528,8 +528,6 @@ loop_unroll_visitor::visit_leave(ir_loop *ir)
    unsigned term_count = 0;
    bool first_term_then_continue = false;
    foreach_in_list(loop_terminator, t, &ls->terminators) {
-      assert(term_count < 2);
-
       ir_if *ir_if = t->ir->as_if();
       assert(ir_if != NULL);