ac/nir: Add vote_ieq/vote_feq lowering pass.

The old vote_eq implementation supported only booleans, but now
we have to support arbitrary values, so use the read_first_invocation
intrinsic + ballot.

I took this as an opportunity to figure out how easy it was to do this
in nir instead of in the nir_to_llvm pass, and it actually turned out
pretty okay IMO. Only creating the pass is some extra code.

Reviewed-by: Dave Airlie <airlied@redhat.com>

src/amd/Makefile.sources

@@ -44,6 +44,7 @@ AMD_COMPILER_FILES = \
 	common/ac_llvm_helper.cpp \
 	common/ac_llvm_util.c \
 	common/ac_llvm_util.h \
+	common/ac_lower_subgroups.c \
 	common/ac_shader_abi.h \
 	common/ac_shader_info.c \
 	common/ac_shader_info.h \

src/amd/common/ac_lower_subgroups.c

@@ -0,0 +1,92 @@
+/*
+ * Copyright © 2018 Google Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "nir/nir.h"
+#include "nir/nir_builder.h"
+
+#include "ac_nir_to_llvm.h"
+
+static nir_ssa_def *ac_lower_subgroups_intrin(nir_builder *b, nir_intrinsic_instr *intrin)
+{
+	switch(intrin->intrinsic) {
+	case nir_intrinsic_vote_ieq:
+	case nir_intrinsic_vote_feq: {
+		nir_intrinsic_instr *rfi =
+			nir_intrinsic_instr_create(b->shader, nir_intrinsic_read_first_invocation);
+		nir_ssa_dest_init(&rfi->instr, &rfi->dest,
+		                  1, intrin->src[0].ssa->bit_size, NULL);
+		nir_src_copy(&rfi->src[0], &intrin->src[0], rfi);
+		rfi->num_components = 1;
+
+		nir_ssa_def *is_ne;
+		if (intrin->intrinsic == nir_intrinsic_vote_feq)
+			is_ne = nir_fne(b, &rfi->dest.ssa, intrin->src[0].ssa);
+		else
+			is_ne = nir_ine(b, &rfi->dest.ssa, intrin->src[0].ssa);
+
+		nir_intrinsic_instr *ballot =
+			nir_intrinsic_instr_create(b->shader, nir_intrinsic_ballot);
+		nir_ssa_dest_init(&ballot->instr, &ballot->dest,
+		                  1, 64, NULL);
+		ballot->src[0] = nir_src_for_ssa(is_ne);
+		ballot->num_components = 1;
+
+		return nir_ieq(b, &ballot->dest.ssa, nir_imm_int64(b, 0));
+	}
+	default:
+		return NULL;
+	}
+}
+
+bool ac_lower_subgroups(struct nir_shader *shader)
+{
+	bool progress = false;
+
+	nir_foreach_function(function, shader) {
+		if (!function->impl)
+			continue;
+
+		nir_builder b;
+		nir_builder_init(&b, function->impl);
+
+		nir_foreach_block(block, function->impl) {
+			nir_foreach_instr_safe(instr, block) {
+				if (instr->type != nir_instr_type_intrinsic)
+					continue;
+
+				nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+				b.cursor = nir_before_instr(instr);
+
+				nir_ssa_def *lower = ac_lower_subgroups_intrin(&b, intrin);
+				if (!lower)
+					continue;
+
+				nir_ssa_def_rewrite_uses(&intrin->dest.ssa, nir_src_for_ssa(lower));
+				nir_instr_remove(instr);
+				progress = true;
+			}
+		}
+	}
+
+	return progress;
+}

src/amd/common/ac_nir_to_llvm.c

@@ -4563,11 +4563,6 @@ static void visit_intrinsic(struct ac_nir_context *ctx,
 		result = LLVMBuildSExt(ctx->ac.builder, tmp, ctx->ac.i32, "");
 		break;
 	}
-	case nir_intrinsic_vote_ieq: {
-		LLVMValueRef tmp = ac_build_vote_eq(&ctx->ac, get_src(ctx, instr->src[0]));
-		result = LLVMBuildSExt(ctx->ac.builder, tmp, ctx->ac.i32, "");
-		break;
-	}
 	default:
 		fprintf(stderr, "Unknown intrinsic: ");
 		nir_print_instr(&instr->instr, stderr);
@@ -6757,6 +6752,9 @@ void ac_nir_translate(struct ac_llvm_context *ac, struct ac_shader_abi *abi,
 	struct ac_nir_context ctx = {};
 	struct nir_function *func;
 
+	/* Last minute passes for both radv & radeonsi */
+	ac_lower_subgroups(nir);
+
 	ctx.ac = *ac;
 	ctx.abi = abi;
 

src/amd/common/ac_nir_to_llvm.h

@@ -235,4 +235,6 @@ void ac_lower_indirect_derefs(struct nir_shader *nir, enum chip_class);
 void ac_nir_translate(struct ac_llvm_context *ac, struct ac_shader_abi *abi,
 		      struct nir_shader *nir);
 
+bool ac_lower_subgroups(struct nir_shader *shader);
+
 #endif /* AC_NIR_TO_LLVM_H */

src/amd/common/meson.build

@@ -35,6 +35,7 @@ amd_common_files = files(
   'ac_llvm_helper.cpp',
   'ac_llvm_util.c',
   'ac_llvm_util.h',
+  'ac_lower_subgroups.c',
   'ac_shader_abi.h',
   'ac_shader_info.c',
   'ac_shader_info.h',