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//===-- addsf3.S - Adds two single precision floating pointer numbers-----===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements the __addsf3 (single precision floating pointer number
// addition with the IEEE-754 default rounding (to nearest, ties to even)
// function for the ARM Thumb1 ISA.
#include "../assembly.h"
#define significandBits 23
#define typeWidth 32
.syntax unified
.p2align 2
DEFINE_AEABI_FUNCTION_ALIAS(__aeabi_fadd, __addsf3)
push {r4, r5, r6, r7, lr}
// Get the absolute value of a and b.
lsls r2, r0, #1
lsls r3, r1, #1
lsrs r2, r2, #1 // aAbs
beq LOCAL_LABEL(a_zero_nan_inf)
lsrs r3, r3, #1 // bAbs
beq LOCAL_LABEL(zero_nan_inf)
// Detect if a or b is infinity or Nan.
lsrs r6, r2, #(significandBits)
lsrs r7, r3, #(significandBits)
cmp r6, #0xFF
beq LOCAL_LABEL(zero_nan_inf)
cmp r7, #0xFF
beq LOCAL_LABEL(zero_nan_inf)
// Swap Rep and Abs so that a and aAbs has the larger absolute value.
cmp r2, r3
bhs LOCAL_LABEL(no_swap)
movs r4, r0
movs r5, r2
movs r0, r1
movs r2, r3
movs r1, r4
movs r3, r5
// Get the significands and shift them to give us round, guard and sticky.
lsls r4, r0, #(typeWidth - significandBits)
lsrs r4, r4, #(typeWidth - significandBits - 3) // aSignificand << 3
lsls r5, r1, #(typeWidth - significandBits)
lsrs r5, r5, #(typeWidth - significandBits - 3) // bSignificand << 3
// Get the implicitBit.
movs r6, #1
lsls r6, r6, #(significandBits + 3)
// Get aExponent and set implicit bit if necessary.
lsrs r2, r2, #(significandBits)
beq LOCAL_LABEL(a_done_implicit_bit)
orrs r4, r6
// Get bExponent and set implicit bit if necessary.
lsrs r3, r3, #(significandBits)
beq LOCAL_LABEL(b_done_implicit_bit)
orrs r5, r6
// Get the difference in exponents.
subs r6, r2, r3
beq LOCAL_LABEL(done_align)
// If b is denormal, then a must be normal as align > 0, and we only need to
// right shift bSignificand by (align - 1) bits.
cmp r3, #0
bne 1f
subs r6, r6, #1
// No longer needs bExponent. r3 is dead here.
// Set sticky bits of b: sticky = bSignificand << (typeWidth - align).
movs r3, #(typeWidth)
subs r3, r3, r6
movs r7, r5
lsls r7, r3
beq 1f
movs r7, #1
// bSignificand = bSignificand >> align | sticky;
lsrs r5, r6
orrs r5, r7
bne LOCAL_LABEL(done_align)
movs r5, #1 // sticky; b is known to be non-zero.
// isSubtraction = (aRep ^ bRep) >> 31;
movs r7, r0
eors r7, r1
lsrs r7, #31
bne LOCAL_LABEL(do_substraction)
// Same sign, do Addition.
// aSignificand += bSignificand;
adds r4, r4, r5
// Check carry bit.
movs r6, #1
lsls r6, r6, #(significandBits + 3 + 1)
movs r7, r4
ands r7, r6
beq LOCAL_LABEL(form_result)
// If the addition carried up, we need to right-shift the result and
// adjust the exponent.
movs r7, r4
movs r6, #1
ands r7, r6 // sticky = aSignificand & 1;
lsrs r4, #1
orrs r4, r7 // result Significand
adds r2, #1 // result Exponent
// If we have overflowed the type, return +/- infinity.
cmp r2, 0xFF
beq LOCAL_LABEL(ret_inf)
// Shift the sign, exponent and significand into place.
lsrs r0, #(typeWidth - 1)
lsls r0, #(typeWidth - 1) // Get Sign.
lsls r2, #(significandBits)
orrs r0, r2
movs r1, r4
lsls r4, #(typeWidth - significandBits - 3)
lsrs r4, #(typeWidth - significandBits)
orrs r0, r4
// Final rounding. The result may overflow to infinity, but that is the
// correct result in that case.
// roundGuardSticky = aSignificand & 0x7;
movs r2, #0x7
ands r1, r2
// if (roundGuardSticky > 0x4) result++;
cmp r1, #0x4
blt LOCAL_LABEL(done_round)
beq 1f
adds r0, #1
pop {r4, r5, r6, r7, pc}
// if (roundGuardSticky == 0x4) result += result & 1;
movs r1, r0
lsrs r1, #1
bcc LOCAL_LABEL(done_round)
adds r0, r0, #1
pop {r4, r5, r6, r7, pc}
subs r4, r4, r5 // aSignificand -= bSignificand;
beq LOCAL_LABEL(ret_zero)
movs r6, r4
cmp r2, 0
beq LOCAL_LABEL(form_result) // if a's exp is 0, no need to normalize.
// If partial cancellation occured, we need to left-shift the result
// and adjust the exponent:
lsrs r6, r6, #(significandBits + 3)
bne LOCAL_LABEL(form_result)
push {r0, r1, r2, r3}
movs r0, r4
bl SYMBOL_NAME(__clzsi2)
movs r5, r0
pop {r0, r1, r2, r3}
// shift = rep_clz(aSignificand) - rep_clz(implicitBit << 3);
subs r5, r5, #(typeWidth - significandBits - 3 - 1)
// aSignificand <<= shift; aExponent -= shift;
lsls r4, r5
subs r2, r2, r5
bgt LOCAL_LABEL(form_result)
// Do normalization if aExponent <= 0.
movs r6, #1
subs r6, r6, r2 // 1 - aExponent;
movs r2, #0 // aExponent = 0;
movs r3, #(typeWidth) // bExponent is dead.
subs r3, r3, r6
movs r7, r4
lsls r7, r3 // stickyBit = (bool)(aSignificant << (typeWidth - align))
beq 1f
movs r7, #1
lsrs r4, r6 // aSignificand >> shift
orrs r4, r7
b LOCAL_LABEL(form_result)
movs r0, #0
pop {r4, r5, r6, r7, pc}
lsrs r3, r3, #1
// Here r2 has aAbs, r3 has bAbs
movs r4, #0xFF
lsls r4, r4, #(significandBits) // Make +inf.
cmp r2, r4
bhi LOCAL_LABEL(a_is_nan)
cmp r3, r4
bhi LOCAL_LABEL(b_is_nan)
cmp r2, r4
bne LOCAL_LABEL(a_is_rational)
// aAbs is INF.
eors r1, r0 // aRep ^ bRep.
movs r6, #1
lsls r6, r6, #(typeWidth - 1) // get sign mask.
cmp r1, r6 // if they only differ on sign bit, it's -INF + INF
beq LOCAL_LABEL(a_is_nan)
pop {r4, r5, r6, r7, pc}
cmp r3, r4
bne LOCAL_LABEL(b_is_rational)
movs r0, r1
pop {r4, r5, r6, r7, pc}
// either a or b or both are zero.
adds r4, r2, r3
beq LOCAL_LABEL(both_zero)
cmp r2, #0 // is absA 0 ?
beq LOCAL_LABEL(ret_b)
pop {r4, r5, r6, r7, pc}
ands r0, r1 // +0 + -0 = +0
pop {r4, r5, r6, r7, pc}
movs r0, r1
pop {r4, r5, r6, r7, pc}
movs r0, r1
movs r1, #1
lsls r1, r1, #(significandBits -1) // r1 is quiet bit.
orrs r0, r1
pop {r4, r5, r6, r7, pc}
movs r4, #0xFF
lsls r4, r4, #(significandBits)
orrs r0, r4
lsrs r0, r0, #(significandBits)
lsls r0, r0, #(significandBits)
pop {r4, r5, r6, r7, pc}