From: Marek Olšák <marek.olsak@amd.com>
Date: Thu, 3 Sep 2020 09:51:17 +0000 (-0400)
Subject: ac/llvm: add better code for isign
X-Git-Url: https://git.libre-soc.org/?p=mesa.git;a=commitdiff_plain;h=70375a9afb0800722509d4a09c94b8b959aeb3fc

ac/llvm: add better code for isign

There are 2 improvements:
- select v_med3_i32
- support vectors

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6284>
---

diff --git a/src/amd/llvm/ac_llvm_build.c b/src/amd/llvm/ac_llvm_build.c
index de9091693c1..a3fa30fc003 100644
--- a/src/amd/llvm/ac_llvm_build.c
+++ b/src/amd/llvm/ac_llvm_build.c
@@ -2751,19 +2751,29 @@ LLVMValueRef ac_build_fract(struct ac_llvm_context *ctx, LLVMValueRef src0,
 				  AC_FUNC_ATTR_READNONE);
 }
 
-LLVMValueRef ac_build_isign(struct ac_llvm_context *ctx, LLVMValueRef src0,
-			    unsigned bitsize)
+static LLVMValueRef ac_const_uint_vec(struct ac_llvm_context *ctx, LLVMTypeRef type, uint64_t value)
 {
-	LLVMTypeRef type = LLVMIntTypeInContext(ctx->context, bitsize);
-	LLVMValueRef zero = LLVMConstInt(type, 0, false);
-	LLVMValueRef one = LLVMConstInt(type, 1, false);
 
-	LLVMValueRef cmp, val;
-	cmp = LLVMBuildICmp(ctx->builder, LLVMIntSGT, src0, zero, "");
-	val = LLVMBuildSelect(ctx->builder, cmp, one, src0, "");
-	cmp = LLVMBuildICmp(ctx->builder, LLVMIntSGE, val, zero, "");
-	val = LLVMBuildSelect(ctx->builder, cmp, val, LLVMConstInt(type, -1, true), "");
-	return val;
+	if (LLVMGetTypeKind(type) == LLVMVectorTypeKind) {
+		LLVMValueRef scalar = LLVMConstInt(LLVMGetElementType(type), value, 0);
+		unsigned vec_size = LLVMGetVectorSize(type);
+		LLVMValueRef *scalars = alloca(vec_size * sizeof(LLVMValueRef*));
+
+		for (unsigned i = 0; i < vec_size; i++)
+			scalars[i] = scalar;
+		return LLVMConstVector(scalars, vec_size);
+	}
+	return LLVMConstInt(type, value, 0);
+}
+
+LLVMValueRef ac_build_isign(struct ac_llvm_context *ctx, LLVMValueRef src0)
+{
+	LLVMTypeRef type = LLVMTypeOf(src0);
+	LLVMValueRef val;
+
+	/* v_med3 is selected only when max is first. (LLVM bug?) */
+	val = ac_build_imax(ctx, src0, ac_const_uint_vec(ctx, type, -1));
+	return ac_build_imin(ctx, val, ac_const_uint_vec(ctx, type, 1));
 }
 
 LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src0,
diff --git a/src/amd/llvm/ac_llvm_build.h b/src/amd/llvm/ac_llvm_build.h
index 764b0565a66..7cb98d06a6e 100644
--- a/src/amd/llvm/ac_llvm_build.h
+++ b/src/amd/llvm/ac_llvm_build.h
@@ -597,10 +597,7 @@ void ac_build_waitcnt(struct ac_llvm_context *ctx, unsigned wait_flags);
 
 LLVMValueRef ac_build_fract(struct ac_llvm_context *ctx, LLVMValueRef src0,
 			   unsigned bitsize);
-
-LLVMValueRef ac_build_isign(struct ac_llvm_context *ctx, LLVMValueRef src0,
-			    unsigned bitsize);
-
+LLVMValueRef ac_build_isign(struct ac_llvm_context *ctx, LLVMValueRef src0);
 LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src0,
 			    unsigned bitsize);
 
diff --git a/src/amd/llvm/ac_nir_to_llvm.c b/src/amd/llvm/ac_nir_to_llvm.c
index 9ad16fba8d3..ddea78180b1 100644
--- a/src/amd/llvm/ac_nir_to_llvm.c
+++ b/src/amd/llvm/ac_nir_to_llvm.c
@@ -822,8 +822,7 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
 		result = ac_build_umin(&ctx->ac, src[0], src[1]);
 		break;
 	case nir_op_isign:
-		result = ac_build_isign(&ctx->ac, src[0],
-					instr->dest.dest.ssa.bit_size);
+		result = ac_build_isign(&ctx->ac, src[0]);
 		break;
 	case nir_op_fsign:
 		src[0] = ac_to_float(&ctx->ac, src[0]);