[Mesa-dev] [PATCH] ac/nir_to_llvm: dont add unrequired swizzle to bcsel src

[Timothy Arceri]

NIR can produce IR that looks like this:

	vec1 1 ssa_51 = ilt ssa_32, ssa_50
	vec4 32 ssa_54 = intrinsic load_deref (ssa_53) (0)
	vec4 32 ssa_57 = intrinsic load_deref (ssa_56) (0)
	vec4 32 ssa_61 = bcsel ssa_51.xxxx, ssa_54, ssa_57

The swizzle on the first bcsel src causes a crash in llvm as it
doesn't seem to expect it. Here we add a special case for the
first bcsel src.
---
 src/amd/common/ac_nir_to_llvm.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 5fb5c8da609..cebf248427c 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -154,13 +154,18 @@ static LLVMBasicBlockRef get_block(struct ac_nir_context *nir,
 
 static LLVMValueRef get_alu_src(struct ac_nir_context *ctx,
                                 nir_alu_src src,
-                                unsigned num_components)
+                                unsigned num_components,
+                                bool is_first_bcsel_src)
 {
 	LLVMValueRef value = get_src(ctx, src.src);
 	bool need_swizzle = false;
 
 	assert(value);
 	unsigned src_components = ac_get_llvm_num_components(value);
+
+	if (is_first_bcsel_src)
+		num_components = 1;
+
 	for (unsigned i = 0; i < num_components; ++i) {
 		assert(src.swizzle[i] < src_components);
 		if (src.swizzle[i] != i)
@@ -584,8 +589,10 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
 		src_components = num_components;
 		break;
 	}
-	for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++)
-		src[i] = get_alu_src(ctx, instr->src[i], src_components);
+	for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
+		src[i] = get_alu_src(ctx, instr->src[i], src_components,
+                                     (instr->op == nir_op_b32csel && i == 0));
+	}
 
 	switch (instr->op) {
 	case nir_op_fmov:
-- 
2.20.1