From 66a14f9c410dd381e478897789d60bc8510be6ee Mon Sep 17 00:00:00 2001
From: Jason Ekstrand <jason@jlekstrand.net>
Date: Mon, 1 Jun 2020 18:01:05 -0500
Subject: [PATCH] spirv: Run repair_ssa if there are discard instructions
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SPIR-V's OpKill is a control-flow instruction but NIR's discard is not.
Therefore, it can be valid SPIR-V to have

    if (...) {
        foo = /* something */
    } else {
        discard;
    }
    use(foo);

without any phi between the definition of foo and its use.  This is not
true in NIR, however, because NIR's discard isn't considered
control-flow.  Arguably, this is a NIR bug but making discard control-
flow is a very deep change that can have serious ans subtle
side-effects.   The easier thing to do is just fix up the SSA in case we
have an OpKill which might have gotten us into the above case.

Fixes dEQP-VK.graphicsfuzz.vectors-and-discard-in-function with the new
NIR dominance validation pass enabled.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5288>
(cherry picked from commit 7cedc4128a1f9d8ecae00ff41ccf1b63e4f3ebd0)
---
 .pick_status.json                | 2 +-
 src/compiler/spirv/vtn_cfg.c     | 3 ++-
 src/compiler/spirv/vtn_private.h | 1 +
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index fffc404ff2b..775dfc2fbb5 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -1048,7 +1048,7 @@
         "description": "spirv: Run repair_ssa if there are discard instructions",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": null
     },
diff --git a/src/compiler/spirv/vtn_cfg.c b/src/compiler/spirv/vtn_cfg.c
index 04eca9baa24..10fe5369eef 100644
--- a/src/compiler/spirv/vtn_cfg.c
+++ b/src/compiler/spirv/vtn_cfg.c
@@ -616,6 +616,7 @@ vtn_process_block(struct vtn_builder *b,
       return NULL;
 
    case SpvOpKill:
+      b->has_kill = true;
       block->branch_type = vtn_branch_type_discard;
       return NULL;
 
@@ -1185,7 +1186,7 @@ vtn_function_emit(struct vtn_builder *b, struct vtn_function *func,
     * 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.
     */
-   if (b->has_loop_continue)
+   if (b->has_loop_continue || b->has_kill)
       nir_repair_ssa_impl(func->impl);
 
    func->emitted = true;
diff --git a/src/compiler/spirv/vtn_private.h b/src/compiler/spirv/vtn_private.h
index 69dbe890938..e8cb65a6697 100644
--- a/src/compiler/spirv/vtn_private.h
+++ b/src/compiler/spirv/vtn_private.h
@@ -679,6 +679,7 @@ struct vtn_builder {
    unsigned func_param_idx;
 
    bool has_loop_continue;
+   bool has_kill;
 
    /* false by default, set to true by the ContractionOff execution mode */
    bool exact;