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-rw-r--r--src/gallium/auxiliary/gallivm/lp_bld_format_float.c85
1 files changed, 65 insertions, 20 deletions
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_format_float.c b/src/gallium/auxiliary/gallivm/lp_bld_format_float.c
index f68a617b810..b87174e4a20 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_format_float.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_format_float.c
@@ -309,33 +309,78 @@ lp_build_smallfloat_to_float(struct gallivm_state *gallivm,
((1 << (mantissa_bits + exponent_bits)) - 1)
<< (23 - mantissa_bits));
srcabs = lp_build_and(&i32_bld, src, maskabs);
- srcabs = LLVMBuildBitCast(builder, srcabs, f32_bld.vec_type, "");
/* now do the actual scaling */
smallexpmask = lp_build_const_int_vec(gallivm, i32_type,
((1 << exponent_bits) - 1) << 23);
i32_floatexpmask = lp_build_const_int_vec(gallivm, i32_type, 0xff << 23);
- /*
- * magic number has exponent new exp bias + (new exp bias - old exp bias),
- * mantissa is 0.
- */
- magic = lp_build_const_int_vec(gallivm, i32_type,
- (255 - (1 << (exponent_bits - 1))) << 23);
- magic = LLVMBuildBitCast(builder, magic, f32_bld.vec_type, "");
- /* adjust exponent and fix denorms */
- res = lp_build_mul(&f32_bld, srcabs, magic);
+ if (0) {
+ /*
+ * Note that this code path, while simpler, will convert small
+ * float denorms to floats according to current cpu denorm mode, if
+ * denorms are disabled it will flush them to zero!
+ * If cpu denorms are enabled, it should be faster though as long as
+ * there's no denorms in the inputs, but if there are actually denorms
+ * it's likely to be an order of magnitude slower (on x86 cpus).
+ */
- /*
- * if exp was max (== NaN or Inf) set new exp to max (keep mantissa),
- * so a simple "or" will do (because exp adjust will leave mantissa intact)
- */
- /* use float compare (better for AVX 8-wide / no AVX2 but else should use int) */
- smallexpmask = LLVMBuildBitCast(builder, smallexpmask, f32_bld.vec_type, "");
- wasinfnan = lp_build_compare(gallivm, f32_type, PIPE_FUNC_GEQUAL, srcabs, smallexpmask);
- res = LLVMBuildBitCast(builder, res, i32_bld.vec_type, "");
- tmp = lp_build_and(&i32_bld, i32_floatexpmask, wasinfnan);
- res = lp_build_or(&i32_bld, tmp, res);
+ srcabs = LLVMBuildBitCast(builder, srcabs, f32_bld.vec_type, "");
+
+ /*
+ * magic number has exponent new exp bias + (new exp bias - old exp bias),
+ * mantissa is 0.
+ */
+ magic = lp_build_const_int_vec(gallivm, i32_type,
+ (255 - (1 << (exponent_bits - 1))) << 23);
+ magic = LLVMBuildBitCast(builder, magic, f32_bld.vec_type, "");
+
+ /* adjust exponent and fix denorms */
+ res = lp_build_mul(&f32_bld, srcabs, magic);
+
+ /*
+ * if exp was max (== NaN or Inf) set new exp to max (keep mantissa),
+ * so a simple "or" will do (because exp adjust will leave mantissa intact)
+ */
+ /* use float compare (better for AVX 8-wide / no AVX2 but else should use int) */
+ smallexpmask = LLVMBuildBitCast(builder, smallexpmask, f32_bld.vec_type, "");
+ wasinfnan = lp_build_compare(gallivm, f32_type, PIPE_FUNC_GEQUAL, srcabs, smallexpmask);
+ res = LLVMBuildBitCast(builder, res, i32_bld.vec_type, "");
+ tmp = lp_build_and(&i32_bld, i32_floatexpmask, wasinfnan);
+ res = lp_build_or(&i32_bld, tmp, res);
+ }
+
+ else {
+ LLVMValueRef exp_one, isdenorm, denorm, normal, exp_adj;
+
+ /* denorm (or zero) if exponent is zero */
+ exp_one = lp_build_const_int_vec(gallivm, i32_type, 1 << 23);
+ isdenorm = lp_build_cmp(&i32_bld, PIPE_FUNC_LESS, srcabs, exp_one);
+
+ /* inf or nan if exponent is max */
+ wasinfnan = lp_build_cmp(&i32_bld, PIPE_FUNC_GEQUAL, srcabs, smallexpmask);
+
+ /* for denormal (or zero), add (== or) magic exp to mantissa (== srcabs) (as int)
+ * then subtract it (as float).
+ * Another option would be to just do inttofp then do a rescale mul.
+ */
+ magic = lp_build_const_int_vec(gallivm, i32_type,
+ (127 - ((1 << (exponent_bits - 1)) - 2)) << 23);
+ denorm = lp_build_or(&i32_bld, srcabs, magic);
+ denorm = LLVMBuildBitCast(builder, denorm, f32_bld.vec_type, "");
+ denorm = lp_build_sub(&f32_bld, denorm,
+ LLVMBuildBitCast(builder, magic, f32_bld.vec_type, ""));
+ denorm = LLVMBuildBitCast(builder, denorm, i32_bld.vec_type, "");
+
+ /* for normals, Infs, Nans fix up exponent */
+ exp_adj = lp_build_const_int_vec(gallivm, i32_type,
+ (127 - ((1 << (exponent_bits - 1)) - 1)) << 23);
+ normal = lp_build_add(&i32_bld, srcabs, exp_adj);
+ tmp = lp_build_and(&i32_bld, wasinfnan, i32_floatexpmask);
+ normal = lp_build_or(&i32_bld, tmp, normal);
+
+ res = lp_build_select(&i32_bld, isdenorm, denorm, normal);
+ }
if (has_sign) {
LLVMValueRef signmask = lp_build_const_int_vec(gallivm, i32_type, 0x80000000);