math/fma: Add fp32 software implementation

Passes CTS on carrizo (when forced to use sw fma) and turks.
Reviewer: Tom Stellard <tstellar@redhat.com>
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

llvm-svn: 334226

libclc/generic/include/clc/math/fma.h

@@ -1,6 +1,7 @@
-#undef fma
-#define fma __clc_fma
+#define __CLC_BODY <clc/math/ternary_decl.inc>
+#define __CLC_FUNCTION fma
 
-#define __CLC_FUNCTION __clc_fma
-#define __CLC_INTRINSIC "llvm.fma"
-#include <clc/math/ternary_intrin.inc>
+#include <clc/math/gentype.inc>
+
+#undef __CLC_BODY
+#undef __CLC_FUNCTION

libclc/generic/include/clc/math/ternary_decl.inc

@@ -0,0 +1 @@
+_CLC_OVERLOAD _CLC_DECL __CLC_GENTYPE __CLC_FUNCTION(__CLC_GENTYPE a, __CLC_GENTYPE b, __CLC_GENTYPE c);

libclc/generic/include/math/clc_fma.h

@@ -0,0 +1,11 @@
+#define __CLC_FUNCTION __clc_fma
+#define __CLC_INTRINSIC "llvm.fma"
+#include <clc/math/ternary_intrin.inc>
+
+#define __FLOAT_ONLY
+#define __CLC_FUNCTION __clc_sw_fma
+#define __CLC_BODY <clc/math/ternary_decl.inc>
+#include <clc/math/gentype.inc>
+#undef __CLC_BODY
+#undef __CLC_FUNCTION
+#undef __FLOAT_ONLY

libclc/generic/lib/SOURCES

@@ -101,6 +101,8 @@ math/exp2.cl
 math/clc_exp10.cl
 math/exp10.cl
 math/fdim.cl
+math/clc_fma.cl
+math/fma.cl
 math/fmax.cl
 math/fmin.cl
 math/clc_fmod.cl

libclc/generic/lib/math/clc_fma.cl

@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2014 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <clc/clc.h>
+
+#include "config.h"
+#include "math.h"
+#include "../clcmacro.h"
+
+struct fp {
+	ulong mantissa;
+	int exponent;
+	uint sign;
+};
+
+_CLC_DEF _CLC_OVERLOAD float __clc_sw_fma(float a, float b, float c)
+{
+	/* special cases */
+	if (isnan(a) || isnan(b) || isnan(c) || isinf(a) || isinf(b))
+		return mad(a, b, c);
+
+	/* If only c is inf, and both a,b are regular numbers, the result is c*/
+	if (isinf(c))
+		return c;
+
+	a = __clc_flush_denormal_if_not_supported(a);
+	b = __clc_flush_denormal_if_not_supported(b);
+	c = __clc_flush_denormal_if_not_supported(c);
+
+	if (c == 0)
+		return a * b;
+
+	struct fp st_a, st_b, st_c;
+
+	st_a.exponent = a == .0f ? 0 : ((as_uint(a) & 0x7f800000) >> 23) - 127;
+	st_b.exponent = b == .0f ? 0 : ((as_uint(b) & 0x7f800000) >> 23) - 127;
+	st_c.exponent = c == .0f ? 0 : ((as_uint(c) & 0x7f800000) >> 23) - 127;
+
+	st_a.mantissa = a == .0f ? 0 : (as_uint(a) & 0x7fffff) | 0x800000;
+	st_b.mantissa = b == .0f ? 0 : (as_uint(b) & 0x7fffff) | 0x800000;
+	st_c.mantissa = c == .0f ? 0 : (as_uint(c) & 0x7fffff) | 0x800000;
+
+	st_a.sign = as_uint(a) & 0x80000000;
+	st_b.sign = as_uint(b) & 0x80000000;
+	st_c.sign = as_uint(c) & 0x80000000;
+
+	// Multiplication.
+	// Move the product to the highest bits to maximize precision
+	// mantissa is 24 bits => product is 48 bits, 2bits non-fraction.
+	// Add one bit for future addition overflow,
+	// add another bit to detect subtraction underflow
+	struct fp st_mul;
+	st_mul.sign = st_a.sign ^ st_b.sign;
+	st_mul.mantissa = (st_a.mantissa * st_b.mantissa) << 14ul;
+	st_mul.exponent = st_mul.mantissa ? st_a.exponent + st_b.exponent : 0;
+
+	// FIXME: Detecting a == 0 || b == 0 above crashed GCN isel
+	if (st_mul.exponent == 0 && st_mul.mantissa == 0)
+		return c;
+
+// Mantissa is 23 fractional bits, shift it the same way as product mantissa
+#define C_ADJUST 37ul
+
+	// both exponents are bias adjusted
+	int exp_diff = st_mul.exponent - st_c.exponent;
+
+	st_c.mantissa <<= C_ADJUST;
+	ulong cutoff_bits = 0;
+	ulong cutoff_mask = (1ul << abs(exp_diff)) - 1ul;
+	if (exp_diff > 0) {
+		cutoff_bits = exp_diff >= 64 ? st_c.mantissa : (st_c.mantissa & cutoff_mask);
+		st_c.mantissa = exp_diff >= 64 ? 0 : (st_c.mantissa >> exp_diff);
+	} else {
+		cutoff_bits = -exp_diff >= 64 ? st_mul.mantissa : (st_mul.mantissa & cutoff_mask);
+		st_mul.mantissa = -exp_diff >= 64 ? 0 : (st_mul.mantissa >> -exp_diff);
+	}
+
+	struct fp st_fma;
+	st_fma.sign = st_mul.sign;
+	st_fma.exponent = max(st_mul.exponent, st_c.exponent);
+	if (st_c.sign == st_mul.sign) {
+		st_fma.mantissa = st_mul.mantissa + st_c.mantissa;
+	} else {
+		// cutoff bits borrow one
+		st_fma.mantissa = st_mul.mantissa - st_c.mantissa - (cutoff_bits && (st_mul.exponent > st_c.exponent) ? 1 : 0);
+	}
+
+	// underflow: st_c.sign != st_mul.sign, and magnitude switches the sign
+	if (st_fma.mantissa > LONG_MAX) {
+		st_fma.mantissa = 0 - st_fma.mantissa;
+		st_fma.sign = st_mul.sign ^ 0x80000000;
+	}
+
+	// detect overflow/underflow
+	int overflow_bits = 3 - clz(st_fma.mantissa);
+
+	// adjust exponent
+	st_fma.exponent += overflow_bits;
+
+	// handle underflow
+	if (overflow_bits < 0) {
+		st_fma.mantissa <<= -overflow_bits;
+		overflow_bits = 0;
+	}
+
+	// rounding
+	ulong trunc_mask = (1ul << (C_ADJUST + overflow_bits)) - 1;
+	ulong trunc_bits = (st_fma.mantissa & trunc_mask) | (cutoff_bits != 0);
+	ulong last_bit = st_fma.mantissa & (1ul << (C_ADJUST + overflow_bits));
+	ulong grs_bits = (0x4ul << (C_ADJUST - 3 + overflow_bits));
+
+	// round to nearest even
+	if ((trunc_bits > grs_bits) ||
+	    (trunc_bits == grs_bits && last_bit != 0))
+		st_fma.mantissa += (1ul << (C_ADJUST + overflow_bits));
+
+	// Shift mantissa back to bit 23
+	st_fma.mantissa = (st_fma.mantissa >> (C_ADJUST + overflow_bits));
+
+	// Detect rounding overflow
+	if (st_fma.mantissa > 0xffffff) {
+		++st_fma.exponent;
+		st_fma.mantissa >>= 1;
+	}
+
+	if (st_fma.mantissa == 0)
+		return .0f;
+
+	// Flating point range limit
+	if (st_fma.exponent > 127)
+		return as_float(as_uint(INFINITY) | st_fma.sign);
+
+	// Flush denormals
+	if (st_fma.exponent <= -127)
+		return as_float(st_fma.sign);
+
+	return as_float(st_fma.sign | ((st_fma.exponent + 127) << 23) | ((uint)st_fma.mantissa & 0x7fffff));
+}
+_CLC_TERNARY_VECTORIZE(_CLC_DEF _CLC_OVERLOAD, float, __clc_sw_fma, float, float, float)

libclc/generic/lib/math/fma.cl

@@ -0,0 +1,7 @@
+#include <clc/clc.h>
+
+#include "math.h"
+#include "math/clc_fma.h"
+
+#define __CLC_BODY <fma.inc>
+#include <clc/math/gentype.inc>

libclc/generic/lib/math/fma.inc

@@ -0,0 +1,7 @@
+_CLC_DEF _CLC_OVERLOAD __CLC_GENTYPE fma(__CLC_GENTYPE a, __CLC_GENTYPE b, __CLC_GENTYPE c) {
+#if __CLC_FPSIZE == 32 && HAVE_HW_FMA32() == 0
+	return __clc_sw_fma(a, b, c);
+#else
+	return __clc_fma(a, b, c);
+#endif
+}