Mesa (master): gallivm: Added support for float to half-float conversion in lp_build_conv.
Jose Fonseca
jrfonseca at kemper.freedesktop.org
Wed Nov 28 19:14:54 UTC 2012
Module: Mesa
Branch: master
Commit: e66ec7c46b310f6b309aa90c1e0e2edd53de3479
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=e66ec7c46b310f6b309aa90c1e0e2edd53de3479
Author: James Benton <jbenton at vmware.com>
Date: Fri Jun 8 18:49:53 2012 +0100
gallivm: Added support for float to half-float conversion in lp_build_conv.
Reviewed-by: Jose Fonseca <jfonseca at vmware.com>
---
src/gallium/auxiliary/gallivm/lp_bld_conv.c | 96 +++++++++++++++++++++++++--
src/gallium/auxiliary/gallivm/lp_bld_conv.h | 5 +-
2 files changed, 94 insertions(+), 7 deletions(-)
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_conv.c b/src/gallium/auxiliary/gallivm/lp_bld_conv.c
index 0399709..af942ad 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_conv.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_conv.c
@@ -78,18 +78,19 @@
* Note this can be performed in 1 instruction if vcvtph2ps exists (sse5 i think?)
* [llvm.x86.vcvtph2ps / _mm_cvtph_ps]
*
- * @param src_type <vector> type of int16
* @param src value to convert
*
* ref http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/
+ * ref https://gist.github.com/2144712
*/
LLVMValueRef
lp_build_half_to_float(struct gallivm_state *gallivm,
- struct lp_type src_type,
- LLVMValueRef src)
+ LLVMValueRef src)
{
- struct lp_type f32_type = lp_type_float_vec(32, 32 * src_type.length);
- struct lp_type i32_type = lp_type_int_vec(32, 32 * src_type.length);
+ int src_length = LLVMGetVectorSize(LLVMTypeOf(src));
+
+ struct lp_type f32_type = lp_type_float_vec(32, 32 * src_length);
+ struct lp_type i32_type = lp_type_int_vec(32, 32 * src_length);
LLVMBuilderRef builder = gallivm->builder;
LLVMTypeRef int_vec_type = lp_build_vec_type(gallivm, i32_type);
@@ -133,6 +134,76 @@ lp_build_half_to_float(struct gallivm_state *gallivm,
/**
+ * Converts float32 to int16 half-float
+ * Note this can be performed in 1 instruction if vcvtps2ph exists (sse5 i think?)
+ * [llvm.x86.vcvtps2ph / _mm_cvtps_ph]
+ *
+ * @param src value to convert
+ *
+ * ref http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/
+ * ref https://gist.github.com/2156668
+ */
+LLVMValueRef
+lp_build_float_to_half(struct gallivm_state *gallivm,
+ LLVMValueRef src)
+{
+ struct lp_type i32_type = lp_type_int_vec(32, 32 * LLVMGetVectorSize(LLVMTypeOf(src)));
+
+ LLVMBuilderRef builder = gallivm->builder;
+ LLVMTypeRef int_vec_type = lp_build_vec_type(gallivm, i32_type);
+
+ struct lp_build_context bld;
+
+ LLVMValueRef result;
+
+ lp_build_context_init(&bld, gallivm, i32_type);
+
+ /* Extra scope because lp_build_min needs a build context, le sigh */
+ {
+ /* Constants */
+ LLVMValueRef i32_13 = lp_build_const_int_vec(gallivm, i32_type, 13);
+ LLVMValueRef i32_16 = lp_build_const_int_vec(gallivm, i32_type, 16);
+ LLVMValueRef i32_mask_fabs = lp_build_const_int_vec(gallivm, i32_type, 0x7fffffff);
+ LLVMValueRef i32_f32infty = lp_build_const_int_vec(gallivm, i32_type, 0xff << 23);
+ LLVMValueRef i32_expinf = lp_build_const_int_vec(gallivm, i32_type, 0xe0 << 23);
+ LLVMValueRef i32_f16max = lp_build_const_int_vec(gallivm, i32_type, 0x8f << 23);
+ LLVMValueRef i32_magic = lp_build_const_int_vec(gallivm, i32_type, 0x0f << 23);
+
+ /* Cast from float32 to int32 */
+ LLVMValueRef f = LLVMBuildBitCast(builder, src, int_vec_type, "");
+
+ /* Remove sign */
+ LLVMValueRef fabs = LLVMBuildAnd(builder, i32_mask_fabs, f, "");
+
+ /* Magic conversion */
+ LLVMValueRef clamped = lp_build_min(&bld, i32_f16max, fabs);
+ LLVMValueRef scaled = LLVMBuildMul(builder, clamped, i32_magic, "");
+
+ /* Make sure Inf/NaN and unormalised survive */
+ LLVMValueRef infnancase = LLVMBuildXor(builder, i32_expinf, fabs, "");
+ LLVMValueRef b_notnormal = lp_build_compare(gallivm, i32_type, PIPE_FUNC_GREATER, fabs, i32_f32infty);
+
+ /* Merge normal / unnormal case */
+ LLVMValueRef merge1 = LLVMBuildAnd(builder, infnancase, b_notnormal, "");
+ LLVMValueRef merge2 = LLVMBuildNot(builder, LLVMBuildAnd(builder, b_notnormal, scaled, ""), "");
+ LLVMValueRef merged = LLVMBuildOr(builder, merge1, merge2, "");
+ LLVMValueRef shifted = LLVMBuildLShr(builder, merged, i32_13, "");
+
+ /* Sign bit */
+ LLVMValueRef justsign = LLVMBuildXor(builder, f, fabs, "");
+ LLVMValueRef signshifted = LLVMBuildLShr(builder, justsign, i32_16, "");
+
+ /* Combine result */
+ result = LLVMBuildOr(builder, shifted, signshifted, "");
+ }
+
+ /* Truncate from 32 bit to 16 bit */
+ i32_type.width = 16;
+ return LLVMBuildTrunc(builder, result, lp_build_vec_type(gallivm, i32_type), "");
+}
+
+
+/**
* Special case for converting clamped IEEE-754 floats to unsigned norms.
*
* The mathematical voodoo below may seem excessive but it is actually
@@ -493,12 +564,25 @@ lp_build_conv(struct gallivm_state *gallivm,
return;
}
+ /* Special case -> 16bit half-float
+ */
+ else if (dst_type.floating && dst_type.width == 16)
+ {
+ /* Only support src as 32bit float currently */
+ assert(src_type.floating && src_type.width == 32);
+
+ for(i = 0; i < num_tmps; ++i)
+ dst[i] = lp_build_float_to_half(gallivm, tmp[i]);
+
+ return;
+ }
+
/* Pre convert half-floats to floats
*/
else if (src_type.floating && src_type.width == 16)
{
for(i = 0; i < num_tmps; ++i)
- tmp[i] = lp_build_half_to_float(gallivm, src_type, tmp[i]);
+ tmp[i] = lp_build_half_to_float(gallivm, tmp[i]);
tmp_type.width = 32;
}
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_conv.h b/src/gallium/auxiliary/gallivm/lp_bld_conv.h
index c830fbe..ef22105 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_conv.h
+++ b/src/gallium/auxiliary/gallivm/lp_bld_conv.h
@@ -44,7 +44,10 @@ struct lp_type;
LLVMValueRef
lp_build_half_to_float(struct gallivm_state *gallivm,
- struct lp_type src_type,
+ LLVMValueRef src);
+
+LLVMValueRef
+lp_build_float_to_half(struct gallivm_state *gallivm,
LLVMValueRef src);
LLVMValueRef
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