From: Andrii Simiklit <andrii.simiklit@globallogic.com>
Date: Tue, 24 Nov 2020 12:28:12 +0000 (+0200)
Subject: spirv: repair ssa defs for switchs with only default case
X-Git-Tag: upstream/21.2.3~5266
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4220befb383112798b1afc1ba13419ed79470cba;p=platform%2Fupstream%2Fmesa.git

spirv: repair ssa defs for switchs with only default case

This fixes OpSwitch corner case when switch doesn't have any targets
just a `default` and SSAs defined in it is used after switch block
directly without phis.

v2: Just use `repair_ssa` for all structured control-flow cases
               ( - Jason Ekstrand <jason@jlekstrand.net>
                 - Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com> )

Closes: #3787
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Signed-off-by: Andrii Simiklit <andrii.simiklit@globallogic.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7755>
---

diff --git a/src/compiler/spirv/vtn_cfg.c b/src/compiler/spirv/vtn_cfg.c
index 8d0794e..dd91352 100644
--- a/src/compiler/spirv/vtn_cfg.c
+++ b/src/compiler/spirv/vtn_cfg.c
@@ -1393,12 +1393,22 @@ vtn_function_emit(struct vtn_builder *b, struct vtn_function *func,
 
    nir_rematerialize_derefs_in_use_blocks_impl(impl);
 
-   /* Continue blocks for loops get inserted before the body of the loop
-    * but instructions in the continue may use SSA defs in the loop body.
-    * Therefore, we need to repair SSA to insert the needed phi nodes.
+   /*
+    * There are some cases where we need to repair SSA to insert
+    * the needed phi nodes:
+    *
+    * - Continue blocks for loops get inserted before the body of the loop
+    *   but instructions in the continue may use SSA defs in the loop body.
+    *
+    * - Early termination instructions `OpKill` and `OpTerminateInvocation`,
+    *   in NIR. They're represented by regular intrinsics with no control-flow
+    *   semantics. This means that the SSA form from the SPIR-V may not
+    *   100% match NIR.
+    *
+    * - Switches with only default case may also define SSA which may
+    *   subsequently be used out of the switch.
     */
-   if (func->nir_func->impl->structured &&
-       (b->has_loop_continue || b->has_early_terminate))
+   if (func->nir_func->impl->structured)
       nir_repair_ssa_impl(impl);
 
    func->emitted = true;