[Mesa-dev] [PATCH] ac: fix exclusive scans on GFX8-GFX9

[Samuel Pitoiset]

This fixes a regression introduced with scan&reduce operations
on GFX10. Note that some subgroups CTS still fail on GFX10 but
I assume it's a different issue.

This fixes dEQP-VK.subgroups.arithmetic.*.subgroupexclusive*.

Fixes: 227c29a80de "amd/common/gfx10: implement scan & reduce operations"
Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 src/amd/common/ac_llvm_build.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/amd/common/ac_llvm_build.c b/src/amd/common/ac_llvm_build.c
index 05871f5ea98..d72eaa2db46 100644
--- a/src/amd/common/ac_llvm_build.c
+++ b/src/amd/common/ac_llvm_build.c
@@ -4221,10 +4221,7 @@ ac_build_scan(struct ac_llvm_context *ctx, nir_op op, LLVMValueRef src, LLVMValu
 	if (ctx->chip_class >= GFX10) {
 		result = inclusive ? src : identity;
 	} else {
-		if (inclusive)
-			result = src;
-		else
-			result = ac_build_dpp(ctx, identity, src, dpp_wf_sr1, 0xf, 0xf, false);
+		result = src;
 	}
 	if (maxprefix <= 1)
 		return result;
@@ -4333,6 +4330,8 @@ ac_build_exclusive_scan(struct ac_llvm_context *ctx, LLVMValueRef src, nir_op op
 		get_reduction_identity(ctx, op, ac_get_type_size(LLVMTypeOf(src)));
 	result = LLVMBuildBitCast(ctx->builder, ac_build_set_inactive(ctx, src, identity),
 				  LLVMTypeOf(identity), "");
+	if (ctx->chip_class <= GFX9)
+		result = ac_build_dpp(ctx, identity, result, dpp_wf_sr1, 0xf, 0xf, false);
 	result = ac_build_scan(ctx, op, result, identity, ctx->wave_size, false);
 
 	return ac_build_wwm(ctx, result);
-- 
2.22.1