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gallivm: Fix lp_build_float_to_half.
The current implementation was close by not fully correct: several operations that should be done in floating point were being done in integer. Fixes piglit fbo-clear-formats GL_ARB_texture_float Reviewed-by: Brian Paul <brianp@vmware.com> Reviewed-by: Roland Scheidegger <sroland@vmware.com>
This commit is contained in:
José Fonseca
parent
b5918d8f1d
commit
9c9c18a395
1 changed files with 75 additions and 30 deletions
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@ -63,15 +63,18 @@
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#include "util/u_debug.h"
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#include "util/u_math.h"
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#include "util/u_half.h"
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#include "util/u_cpu_detect.h"
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#include "lp_bld_type.h"
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#include "lp_bld_const.h"
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#include "lp_bld_arit.h"
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#include "lp_bld_bitarit.h"
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#include "lp_bld_pack.h"
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#include "lp_bld_conv.h"
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#include "lp_bld_logic.h"
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#include "lp_bld_intr.h"
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#include "lp_bld_printf.h"
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@ -220,64 +223,106 @@ lp_build_half_to_float(struct gallivm_state *gallivm,
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*
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* ref http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/
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* ref https://gist.github.com/2156668
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*
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* XXX: This is an approximation. It is faster but certain NaNs are converted to
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* infinity, and rounding is not correct.
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*/
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LLVMValueRef
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lp_build_float_to_half(struct gallivm_state *gallivm,
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LLVMValueRef src)
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{
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struct lp_type i32_type = lp_type_int_vec(32, 32 * LLVMGetVectorSize(LLVMTypeOf(src)));
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LLVMBuilderRef builder = gallivm->builder;
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LLVMTypeRef int_vec_type = lp_build_vec_type(gallivm, i32_type);
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struct lp_build_context bld;
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LLVMTypeRef f32_vec_type = LLVMTypeOf(src);
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unsigned length = LLVMGetTypeKind(f32_vec_type) == LLVMVectorTypeKind
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? LLVMGetVectorSize(f32_vec_type) : 1;
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struct lp_type f32_type = lp_type_float_vec(32, 32 * length);
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struct lp_type u32_type = lp_type_uint_vec(32, 32 * length);
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struct lp_type i16_type = lp_type_int_vec(16, 16 * length);
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LLVMTypeRef u32_vec_type = lp_build_vec_type(gallivm, u32_type);
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LLVMTypeRef i16_vec_type = lp_build_vec_type(gallivm, i16_type);
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struct lp_build_context f32_bld;
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struct lp_build_context u32_bld;
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LLVMValueRef result;
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lp_build_context_init(&bld, gallivm, i32_type);
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lp_build_context_init(&f32_bld, gallivm, f32_type);
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lp_build_context_init(&u32_bld, gallivm, u32_type);
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/* Extra scope because lp_build_min needs a build context, le sigh */
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{
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/* Constants */
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LLVMValueRef i32_13 = lp_build_const_int_vec(gallivm, i32_type, 13);
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LLVMValueRef i32_16 = lp_build_const_int_vec(gallivm, i32_type, 16);
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LLVMValueRef i32_mask_fabs = lp_build_const_int_vec(gallivm, i32_type, 0x7fffffff);
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LLVMValueRef i32_f32infty = lp_build_const_int_vec(gallivm, i32_type, 0xff << 23);
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LLVMValueRef i32_expinf = lp_build_const_int_vec(gallivm, i32_type, 0xe0 << 23);
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LLVMValueRef i32_f16max = lp_build_const_int_vec(gallivm, i32_type, 0x8f << 23);
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LLVMValueRef i32_magic = lp_build_const_int_vec(gallivm, i32_type, 0x0f << 23);
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LLVMValueRef u32_f32inf = lp_build_const_int_vec(gallivm, u32_type, 0xff << 23);
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LLVMValueRef u32_expinf = lp_build_const_int_vec(gallivm, u32_type, 0xe0 << 23);
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LLVMValueRef f32_f16max = lp_build_const_vec(gallivm, f32_type, 65536.0); // 0x8f << 23
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LLVMValueRef f32_magic = lp_build_const_vec(gallivm, f32_type, 1.92592994e-34); // 0x0f << 23
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/* Cast from float32 to int32 */
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LLVMValueRef f = LLVMBuildBitCast(builder, src, int_vec_type, "");
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LLVMValueRef f = LLVMBuildBitCast(builder, src, u32_vec_type, "");
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/* Remove sign */
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LLVMValueRef fabs = LLVMBuildAnd(builder, i32_mask_fabs, f, "");
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LLVMValueRef srcabs = lp_build_abs(&f32_bld, src);
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LLVMValueRef fabs = LLVMBuildBitCast(builder, srcabs, u32_vec_type, "");
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/* Magic conversion */
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LLVMValueRef clamped = lp_build_min(&bld, i32_f16max, fabs);
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LLVMValueRef scaled = LLVMBuildMul(builder, clamped, i32_magic, "");
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LLVMValueRef clamped = lp_build_min(&f32_bld, f32_f16max, srcabs);
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LLVMValueRef scaled = LLVMBuildBitCast(builder,
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LLVMBuildFMul(builder,
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clamped,
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f32_magic,
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""),
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u32_vec_type,
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"");
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/* Make sure Inf/NaN and unormalised survive */
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LLVMValueRef infnancase = LLVMBuildXor(builder, i32_expinf, fabs, "");
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LLVMValueRef b_notnormal = lp_build_compare(gallivm, i32_type, PIPE_FUNC_GREATER, fabs, i32_f32infty);
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LLVMValueRef infnancase = LLVMBuildXor(builder, u32_expinf, fabs, "");
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LLVMValueRef b_notnormal = lp_build_compare(gallivm, f32_type, PIPE_FUNC_GEQUAL,
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srcabs,
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LLVMBuildBitCast(builder, u32_f32inf, f32_vec_type, ""));
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/* Merge normal / unnormal case */
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LLVMValueRef merge1 = LLVMBuildAnd(builder, infnancase, b_notnormal, "");
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LLVMValueRef merge2 = LLVMBuildNot(builder, LLVMBuildAnd(builder, b_notnormal, scaled, ""), "");
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LLVMValueRef merged = LLVMBuildOr(builder, merge1, merge2, "");
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LLVMValueRef shifted = LLVMBuildLShr(builder, merged, i32_13, "");
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LLVMValueRef merged = lp_build_select(&u32_bld, b_notnormal, infnancase, scaled);
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LLVMValueRef shifted = lp_build_shr_imm(&u32_bld, merged, 13);
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/* Sign bit */
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LLVMValueRef justsign = LLVMBuildXor(builder, f, fabs, "");
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LLVMValueRef signshifted = LLVMBuildLShr(builder, justsign, i32_16, "");
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LLVMValueRef signshifted = lp_build_shr_imm(&u32_bld, justsign, 16);
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/* Combine result */
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result = LLVMBuildOr(builder, shifted, signshifted, "");
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}
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/* Truncate from 32 bit to 16 bit */
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i32_type.width = 16;
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return LLVMBuildTrunc(builder, result, lp_build_vec_type(gallivm, i32_type), "");
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result = LLVMBuildTrunc(builder, result, i16_vec_type, "");
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/*
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* Debugging code.
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*/
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if (0) {
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LLVMTypeRef i32t = LLVMInt32TypeInContext(gallivm->context);
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LLVMTypeRef i16t = LLVMInt16TypeInContext(gallivm->context);
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LLVMTypeRef f32t = LLVMFloatTypeInContext(gallivm->context);
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LLVMValueRef ref_result = LLVMGetUndef(LLVMVectorType(i16t, length));
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unsigned i;
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LLVMTypeRef func_type = LLVMFunctionType(i16t, &f32t, 1, 0);
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LLVMValueRef func = lp_build_const_int_pointer(gallivm, func_to_pointer((func_pointer)util_float_to_half));
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func = LLVMBuildBitCast(builder, func, LLVMPointerType(func_type, 0), "util_float_to_half");
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for (i = 0; i < length; ++i) {
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LLVMValueRef index = LLVMConstInt(i32t, i, 0);
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LLVMValueRef f32 = LLVMBuildExtractElement(builder, src, index, "");
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#if 0
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/* XXX: not really supported by backends */
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LLVMValueRef f16 = lp_build_intrinsic_unary(builder, "llvm.convert.to.fp16", i16t, f32);
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#else
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LLVMValueRef f16 = LLVMBuildCall(builder, func, &f32, 1, "");
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#endif
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ref_result = LLVMBuildInsertElement(builder, ref_result, f16, index, "");
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}
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lp_build_print_value(gallivm, "src = ", src);
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lp_build_print_value(gallivm, "llvm = ", result);
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lp_build_print_value(gallivm, "util = ", ref_result);
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lp_build_printf(gallivm, "\n");
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}
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return result;
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}
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