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ac/llvm: add better code for fsign

Browse source 
There are 2 improvements:
- better code for 16, 32, and 64 bits
- vector support for 16 and 32 bits

Totals:
SGPRS: 2639738 -> 2625882 (-0.52 %)
VGPRS: 1534120 -> 1533916 (-0.01 %)
Spilled SGPRs: 3541 -> 3557 (0.45 %)
Spilled VGPRs: 33 -> 33 (0.00 %)
Private memory VGPRs: 256 -> 256 (0.00 %)
Scratch size: 292 -> 292 (0.00 %) dwords per thread
Code Size: 55640332 -> 55384892 (-0.46 %) bytes
Max Waves: 964785 -> 964857 (0.01 %)

Totals from affected shaders:
SGPRS: 377352 -> 363496 (-3.67 %)
VGPRS: 209800 -> 209596 (-0.10 %)
Spilled SGPRs: 1979 -> 1995 (0.81 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 256 -> 256 (0.00 %)
Scratch size: 256 -> 256 (0.00 %) dwords per thread
Code Size: 12549300 -> 12293860 (-2.04 %) bytes
Max Waves: 105762 -> 105834 (0.07 %)

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6284>
This commit is contained in:
Marek Olšák 2020-09-03 05:31:36 -04:00 • committed by Marge Bot
parent ca74603b4f
commit d9a77f9ca3
5 changed files with 73 additions and 26 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

64
src/amd/llvm/ac_llvm_build.c
View file

@ -2776,31 +2776,53 @@ LLVMValueRef ac_build_isign(struct ac_llvm_context *ctx, LLVMValueRef src0)
return ac_build_imin(ctx, val, ac_const_uint_vec(ctx, type, 1));
}
LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src0,
unsigned bitsize)
static LLVMValueRef ac_eliminate_negative_zero(struct ac_llvm_context *ctx, LLVMValueRef val)
{
LLVMValueRef cmp, val, zero, one;
LLVMTypeRef type;
ac_enable_signed_zeros(ctx);
/* (val + 0) converts negative zero to positive zero. */
val = LLVMBuildFAdd(ctx->builder, val, LLVMConstNull(LLVMTypeOf(val)), "");
ac_disable_signed_zeros(ctx);
return val;
}
if (bitsize == 16) {
type = ctx->f16;
zero = ctx->f16_0;
one = ctx->f16_1;
} else if (bitsize == 32) {
type = ctx->f32;
zero = ctx->f32_0;
one = ctx->f32_1;
} else {
type = ctx->f64;
zero = ctx->f64_0;
one = ctx->f64_1;
LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src)
{
LLVMTypeRef type = LLVMTypeOf(src);
LLVMValueRef pos, neg, dw[2], val;
unsigned bitsize = ac_get_elem_bits(ctx, type);
/* The standard version leads to this:
* v_cmp_ngt_f32_e64 s[0:1], s4, 0 ; D40B0000 00010004
* v_cndmask_b32_e64 v4, 1.0, s4, s[0:1] ; D5010004 000008F2
* v_cmp_le_f32_e32 vcc, 0, v4 ; 7C060880
* v_cndmask_b32_e32 v4, -1.0, v4, vcc ; 020808F3
*
* The isign version:
* v_add_f32_e64 v4, s4, 0 ; D5030004 00010004
* v_med3_i32 v4, v4, -1, 1 ; D5580004 02058304
* v_cvt_f32_i32_e32 v4, v4 ; 7E080B04
*
* (src0 + 0) converts negative zero to positive zero.
* After that, int(fsign(x)) == isign(floatBitsToInt(x)).
*
* For FP64, use the standard version, which doesn't suffer from the huge DP rate
* reduction. (FP64 comparisons are as fast as int64 comparisons)
*/
if (bitsize == 16 || bitsize == 32) {
val = ac_to_integer(ctx, ac_eliminate_negative_zero(ctx, src));
val = ac_build_isign(ctx, val);
return LLVMBuildSIToFP(ctx->builder, val, type, "");
}
cmp = LLVMBuildFCmp(ctx->builder, LLVMRealOGT, src0, zero, "");
val = LLVMBuildSelect(ctx->builder, cmp, one, src0, "");
cmp = LLVMBuildFCmp(ctx->builder, LLVMRealOGE, val, zero, "");
val = LLVMBuildSelect(ctx->builder, cmp, val, LLVMConstReal(type, -1.0), "");
return val;
assert(bitsize == 64);
pos = LLVMBuildFCmp(ctx->builder, LLVMRealOGT, src, ctx->f64_0, "");
neg = LLVMBuildFCmp(ctx->builder, LLVMRealOLT, src, ctx->f64_0, "");
dw[0] = ctx->i32_0;
dw[1] = LLVMBuildSelect(ctx->builder, pos, LLVMConstInt(ctx->i32, 0x3FF00000, 0),
LLVMBuildSelect(ctx->builder, neg,
LLVMConstInt(ctx->i32, 0xBFF00000, 0),
ctx->i32_0, ""), "");
return LLVMBuildBitCast(ctx->builder, ac_build_gather_values(ctx, dw, 2), ctx->f64, "");
}
LLVMValueRef ac_build_bit_count(struct ac_llvm_context *ctx, LLVMValueRef src0)

4
src/amd/llvm/ac_llvm_build.h
View file

@ -598,9 +598,7 @@ 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);
LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src0,
unsigned bitsize);
LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src);
LLVMValueRef ac_build_bit_count(struct ac_llvm_context *ctx, LLVMValueRef src0);
LLVMValueRef ac_build_bitfield_reverse(struct ac_llvm_context *ctx,

25
src/amd/llvm/ac_llvm_helper.cpp
View file

@ -121,6 +121,31 @@ LLVMBuilderRef ac_create_builder(LLVMContextRef ctx,
return builder;
}
void ac_enable_signed_zeros(struct ac_llvm_context *ctx)
{
if (ctx->float_mode == AC_FLOAT_MODE_DEFAULT_OPENGL) {
auto *b = llvm::unwrap(ctx->builder);
llvm::FastMathFlags flags = b->getFastMathFlags();
/* This disables the optimization of (x + 0), which is used
* to convert negative zero to positive zero.
*/
flags.setNoSignedZeros(false);
b->setFastMathFlags(flags);
}
}
void ac_disable_signed_zeros(struct ac_llvm_context *ctx)
{
if (ctx->float_mode == AC_FLOAT_MODE_DEFAULT_OPENGL) {
auto *b = llvm::unwrap(ctx->builder);
llvm::FastMathFlags flags = b->getFastMathFlags();
flags.setNoSignedZeros();
b->setFastMathFlags(flags);
}
}
LLVMTargetLibraryInfoRef
ac_create_target_library_info(const char *triple)
{

3
src/amd/llvm/ac_llvm_util.h
View file

@ -37,6 +37,7 @@ extern "C" {
#endif
struct ac_compiler_passes;
struct ac_llvm_context;
enum ac_func_attr {
AC_FUNC_ATTR_ALWAYSINLINE = (1 << 0),
@ -109,6 +110,8 @@ LLVMModuleRef ac_create_module(LLVMTargetMachineRef tm, LLVMContextRef ctx);
LLVMBuilderRef ac_create_builder(LLVMContextRef ctx,
enum ac_float_mode float_mode);
void ac_enable_signed_zeros(struct ac_llvm_context *ctx);
void ac_disable_signed_zeros(struct ac_llvm_context *ctx);
void
ac_llvm_add_target_dep_function_attr(LLVMValueRef F,

3
src/amd/llvm/ac_nir_to_llvm.c
View file

@ -826,8 +826,7 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
break;
case nir_op_fsign:
src[0] = ac_to_float(&ctx->ac, src[0]);
result = ac_build_fsign(&ctx->ac, src[0],
instr->dest.dest.ssa.bit_size);
result = ac_build_fsign(&ctx->ac, src[0]);
break;
case nir_op_ffloor:
result = emit_intrin_1f_param(&ctx->ac, "llvm.floor",