amd/llvm: Refactor ac_build_scan.

Split out the logic for exclusive scans into a separate function
that makes clear what it does instead of having this opaque 60
line if.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>

1 files changed, 51 insertions, 40 deletions

diff --git a/src/amd/llvm/ac_llvm_build.c b/src/amd/llvm/ac_llvm_build.c
index cf6eda30e2c..47c27893fe5 100644
--- a/src/amd/llvm/ac_llvm_build.c
+++ b/src/amd/llvm/ac_llvm_build.c
@@ -4045,18 +4045,17 @@ ac_build_alu_op(struct ac_llvm_context *ctx, LLVMValueRef lhs, LLVMValueRef rhs,
 }
 
 /**
+ * \param src The value to shift.
+ * \param identity The value to use the first lane.
  * \param maxprefix specifies that the result only needs to be correct for a
  *     prefix of this many threads
+ * \return src, shifted 1 lane up, and identity shifted into lane 0.
  */
 static LLVMValueRef
-ac_build_scan(struct ac_llvm_context *ctx, nir_op op, LLVMValueRef src, LLVMValueRef identity,
-	      unsigned maxprefix, bool inclusive)
+ac_wavefront_shift_right_1(struct ac_llvm_context *ctx, LLVMValueRef src,
+                           LLVMValueRef identity, unsigned maxprefix)
 {
-	LLVMValueRef result, tmp;
-
-	if (inclusive) {
-		result = src;
-	} else if (ctx->chip_class >= GFX10) {
+	if (ctx->chip_class >= GFX10) {
 		/* wavefront shift_right by 1 on GFX10 (emulate dpp_wf_sr1) */
 		LLVMValueRef active, tmp1, tmp2;
 		LLVMValueRef tid = ac_get_thread_id(ctx);
@@ -4079,45 +4078,57 @@ ac_build_scan(struct ac_llvm_context *ctx, nir_op op, LLVMValueRef src, LLVMValu
 							   LLVMBuildAnd(ctx->builder, tid,
 									LLVMConstInt(ctx->i32, 0x1f, false), ""),
 							   LLVMConstInt(ctx->i32, 0x10, false), ""), "");
-			src = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
+			return LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
 		} else if (maxprefix > 16) {
 			active = LLVMBuildICmp(ctx->builder, LLVMIntEQ, tid,
 					       LLVMConstInt(ctx->i32, 16, false), "");
 
-			src = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
+			return LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
 		}
-
-		result = src;
 	} else if (ctx->chip_class >= GFX8) {
-		src = ac_build_dpp(ctx, identity, src, dpp_wf_sr1, 0xf, 0xf, false);
-		result = src;
-	} else {
-		/* wavefront shift_right by 1 on SI/CI */
-		LLVMValueRef active, tmp1, tmp2;
-		LLVMValueRef tid = ac_get_thread_id(ctx);
-		tmp1 = ac_build_ds_swizzle(ctx, src, (1 << 15) | dpp_quad_perm(0, 0, 1, 2));
-		tmp2 = ac_build_ds_swizzle(ctx, src, ds_pattern_bitmode(0x18, 0x03, 0x00));
-		active = LLVMBuildICmp(ctx->builder, LLVMIntEQ,
-				       LLVMBuildAnd(ctx->builder, tid, LLVMConstInt(ctx->i32, 0x7, 0), ""),
-				       LLVMConstInt(ctx->i32, 0x4, 0), "");
-		tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
-		tmp2 = ac_build_ds_swizzle(ctx, src, ds_pattern_bitmode(0x10, 0x07, 0x00));
-		active = LLVMBuildICmp(ctx->builder, LLVMIntEQ,
-				       LLVMBuildAnd(ctx->builder, tid, LLVMConstInt(ctx->i32, 0xf, 0), ""),
-				       LLVMConstInt(ctx->i32, 0x8, 0), "");
-		tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
-		tmp2 = ac_build_ds_swizzle(ctx, src, ds_pattern_bitmode(0x00, 0x0f, 0x00));
-		active = LLVMBuildICmp(ctx->builder, LLVMIntEQ,
-				       LLVMBuildAnd(ctx->builder, tid, LLVMConstInt(ctx->i32, 0x1f, 0), ""),
-				       LLVMConstInt(ctx->i32, 0x10, 0), "");
-		tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
-		tmp2 = ac_build_readlane(ctx, src, LLVMConstInt(ctx->i32, 31, 0));
-		active = LLVMBuildICmp(ctx->builder, LLVMIntEQ, tid, LLVMConstInt(ctx->i32, 32, 0), "");
-		tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
-		active = LLVMBuildICmp(ctx->builder, LLVMIntEQ, tid, LLVMConstInt(ctx->i32, 0, 0), "");
-		src = LLVMBuildSelect(ctx->builder, active, identity, tmp1, "");
-		result = src;
-        }
+		return ac_build_dpp(ctx, identity, src, dpp_wf_sr1, 0xf, 0xf, false);
+	}
+
+	/* wavefront shift_right by 1 on SI/CI */
+	LLVMValueRef active, tmp1, tmp2;
+	LLVMValueRef tid = ac_get_thread_id(ctx);
+	tmp1 = ac_build_ds_swizzle(ctx, src, (1 << 15) | dpp_quad_perm(0, 0, 1, 2));
+	tmp2 = ac_build_ds_swizzle(ctx, src, ds_pattern_bitmode(0x18, 0x03, 0x00));
+	active = LLVMBuildICmp(ctx->builder, LLVMIntEQ,
+			       LLVMBuildAnd(ctx->builder, tid, LLVMConstInt(ctx->i32, 0x7, 0), ""),
+			       LLVMConstInt(ctx->i32, 0x4, 0), "");
+	tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
+	tmp2 = ac_build_ds_swizzle(ctx, src, ds_pattern_bitmode(0x10, 0x07, 0x00));
+	active = LLVMBuildICmp(ctx->builder, LLVMIntEQ,
+			       LLVMBuildAnd(ctx->builder, tid, LLVMConstInt(ctx->i32, 0xf, 0), ""),
+			       LLVMConstInt(ctx->i32, 0x8, 0), "");
+	tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
+	tmp2 = ac_build_ds_swizzle(ctx, src, ds_pattern_bitmode(0x00, 0x0f, 0x00));
+	active = LLVMBuildICmp(ctx->builder, LLVMIntEQ,
+			       LLVMBuildAnd(ctx->builder, tid, LLVMConstInt(ctx->i32, 0x1f, 0), ""),
+			       LLVMConstInt(ctx->i32, 0x10, 0), "");
+	tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
+	tmp2 = ac_build_readlane(ctx, src, LLVMConstInt(ctx->i32, 31, 0));
+	active = LLVMBuildICmp(ctx->builder, LLVMIntEQ, tid, LLVMConstInt(ctx->i32, 32, 0), "");
+	tmp1 = LLVMBuildSelect(ctx->builder, active, tmp2, tmp1, "");
+	active = LLVMBuildICmp(ctx->builder, LLVMIntEQ, tid, LLVMConstInt(ctx->i32, 0, 0), "");
+	return LLVMBuildSelect(ctx->builder, active, identity, tmp1, "");
+}
+
+/**
+ * \param maxprefix specifies that the result only needs to be correct for a
+ *     prefix of this many threads
+ */
+static LLVMValueRef
+ac_build_scan(struct ac_llvm_context *ctx, nir_op op, LLVMValueRef src, LLVMValueRef identity,
+	      unsigned maxprefix, bool inclusive)
+{
+	LLVMValueRef result, tmp;
+
+	if (!inclusive)
+		src = ac_wavefront_shift_right_1(ctx, src, identity, maxprefix);
+
+	result = src;
 
 	if (ctx->chip_class <= GFX7) {
 		assert(maxprefix == 64);