[Mesa-dev] [PATCH 15/18] nir: Fix OpAtomicCounterIDecrement for uniform atomic counters

[Alejandro Piñeiro]

From: Antia Puentes <apuentes at igalia.com>

>From the SPIR-V specification, OpAtomicIDecrement:
"The instruction's result is the Original Value."

However, we were implementing it, for uniform atomic counters, as a
pre-decrement operation.

Renamed the former nir intrinsic 'atomic_counter_dec*' to
'atomic_counter_pre_dec*' for clarification purposes, as it implements
a pre-decrement operation as specified for OpenGL.

Added a new nir intrinsic 'atomic_counter_pos_dec*' which implements a
post-decrement operation as required by SPIR-V.
---
 src/compiler/glsl/gl_nir_lower_atomics.c     | 8 ++++++--
 src/compiler/glsl/glsl_to_nir.cpp            | 4 ++--
 src/compiler/nir/nir_intrinsics.py           | 3 ++-
 src/compiler/nir/nir_lower_atomics_to_ssbo.c | 8 +++++---
 src/compiler/spirv/spirv_to_nir.c            | 2 +-
 5 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/compiler/glsl/gl_nir_lower_atomics.c b/src/compiler/glsl/gl_nir_lower_atomics.c
index 293730966fd..73d058f3902 100644
--- a/src/compiler/glsl/gl_nir_lower_atomics.c
+++ b/src/compiler/glsl/gl_nir_lower_atomics.c
@@ -53,8 +53,12 @@ lower_deref_instr(nir_builder *b, nir_intrinsic_instr *instr,
       op = nir_intrinsic_atomic_counter_inc;
       break;
 
-   case nir_intrinsic_atomic_counter_dec_deref:
-      op = nir_intrinsic_atomic_counter_dec;
+   case nir_intrinsic_atomic_counter_pre_dec_deref:
+      op = nir_intrinsic_atomic_counter_pre_dec;
+      break;
+
+   case nir_intrinsic_atomic_counter_pos_dec_deref:
+      op = nir_intrinsic_atomic_counter_pos_dec;
       break;
 
    case nir_intrinsic_atomic_counter_add_deref:
diff --git a/src/compiler/glsl/glsl_to_nir.cpp b/src/compiler/glsl/glsl_to_nir.cpp
index d3a3fb9b085..2d76c7e6cfe 100644
--- a/src/compiler/glsl/glsl_to_nir.cpp
+++ b/src/compiler/glsl/glsl_to_nir.cpp
@@ -630,7 +630,7 @@ nir_visitor::visit(ir_call *ir)
          op = nir_intrinsic_atomic_counter_inc_deref;
          break;
       case ir_intrinsic_atomic_counter_predecrement:
-         op = nir_intrinsic_atomic_counter_dec_deref;
+         op = nir_intrinsic_atomic_counter_pre_dec_deref;
          break;
       case ir_intrinsic_atomic_counter_add:
          op = nir_intrinsic_atomic_counter_add_deref;
@@ -831,7 +831,7 @@ nir_visitor::visit(ir_call *ir)
       switch (op) {
       case nir_intrinsic_atomic_counter_read_deref:
       case nir_intrinsic_atomic_counter_inc_deref:
-      case nir_intrinsic_atomic_counter_dec_deref:
+      case nir_intrinsic_atomic_counter_pre_dec_deref:
       case nir_intrinsic_atomic_counter_add_deref:
       case nir_intrinsic_atomic_counter_min_deref:
       case nir_intrinsic_atomic_counter_max_deref:
diff --git a/src/compiler/nir/nir_intrinsics.py b/src/compiler/nir/nir_intrinsics.py
index d9d0bbdfccf..c5cbc09c598 100644
--- a/src/compiler/nir/nir_intrinsics.py
+++ b/src/compiler/nir/nir_intrinsics.py
@@ -270,7 +270,8 @@ def atomic3(name):
     intrinsic(name, src_comp=[1, 1, 1], dest_comp=1, indices=[BASE])
 
 atomic("atomic_counter_inc")
-atomic("atomic_counter_dec")
+atomic("atomic_counter_pre_dec")
+atomic("atomic_counter_pos_dec")
 atomic("atomic_counter_read", flags=[CAN_ELIMINATE])
 atomic2("atomic_counter_add")
 atomic2("atomic_counter_min")
diff --git a/src/compiler/nir/nir_lower_atomics_to_ssbo.c b/src/compiler/nir/nir_lower_atomics_to_ssbo.c
index 934ae81d750..34ac9fce40a 100644
--- a/src/compiler/nir/nir_lower_atomics_to_ssbo.c
+++ b/src/compiler/nir/nir_lower_atomics_to_ssbo.c
@@ -71,7 +71,8 @@ lower_instr(nir_intrinsic_instr *instr, unsigned ssbo_offset, nir_builder *b)
       return true;
    case nir_intrinsic_atomic_counter_inc:
    case nir_intrinsic_atomic_counter_add:
-   case nir_intrinsic_atomic_counter_dec:
+   case nir_intrinsic_atomic_counter_pre_dec:
+   case nir_intrinsic_atomic_counter_pos_dec:
       /* inc and dec get remapped to add: */
       op = nir_intrinsic_ssbo_atomic_add;
       break;
@@ -119,7 +120,8 @@ lower_instr(nir_intrinsic_instr *instr, unsigned ssbo_offset, nir_builder *b)
       nir_src_copy(&new_instr->src[1], &instr->src[0], new_instr);
       new_instr->src[2] = nir_src_for_ssa(temp);
       break;
-   case nir_intrinsic_atomic_counter_dec:
+   case nir_intrinsic_atomic_counter_pre_dec:
+   case nir_intrinsic_atomic_counter_pos_dec:
       /* remapped to ssbo_atomic_add: { buffer_idx, offset, -1 } */
       /* NOTE semantic difference so we adjust the return value below */
       temp = nir_imm_int(b, -1);
@@ -148,7 +150,7 @@ lower_instr(nir_intrinsic_instr *instr, unsigned ssbo_offset, nir_builder *b)
    nir_instr_insert_before(&instr->instr, &new_instr->instr);
    nir_instr_remove(&instr->instr);
 
-   if (instr->intrinsic == nir_intrinsic_atomic_counter_dec) {
+   if (instr->intrinsic == nir_intrinsic_atomic_counter_pre_dec) {
       b->cursor = nir_after_instr(&new_instr->instr);
       nir_ssa_def *result = nir_iadd(b, &new_instr->dest.ssa, temp);
       nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(result));
diff --git a/src/compiler/spirv/spirv_to_nir.c b/src/compiler/spirv/spirv_to_nir.c
index 9d2f57cef94..b1ec0b892cb 100644
--- a/src/compiler/spirv/spirv_to_nir.c
+++ b/src/compiler/spirv/spirv_to_nir.c
@@ -2519,7 +2519,7 @@ get_uniform_nir_atomic_op(struct vtn_builder *b, SpvOp opcode)
    OP(AtomicExchange,         exchange)
    OP(AtomicCompareExchange,  comp_swap)
    OP(AtomicIIncrement,       inc_deref)
-   OP(AtomicIDecrement,       dec_deref)
+   OP(AtomicIDecrement,       pos_dec_deref)
    OP(AtomicIAdd,             add_deref)
    OP(AtomicISub,             add_deref)
    OP(AtomicUMin,             min_deref)
-- 
2.14.1