forked from OSchip/llvm-project
131 lines
5.0 KiB
ArmAsm
131 lines
5.0 KiB
ArmAsm
//===-- comparesf2.S - Implement single-precision soft-float comparisons --===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is dual licensed under the MIT and the University of Illinois Open
|
|
// Source Licenses. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the following soft-fp_t comparison routines:
|
|
//
|
|
// __eqsf2 __gesf2 __unordsf2
|
|
// __lesf2 __gtsf2
|
|
// __ltsf2
|
|
// __nesf2
|
|
//
|
|
// The semantics of the routines grouped in each column are identical, so there
|
|
// is a single implementation for each, with multiple names.
|
|
//
|
|
// The routines behave as follows:
|
|
//
|
|
// __lesf2(a,b) returns -1 if a < b
|
|
// 0 if a == b
|
|
// 1 if a > b
|
|
// 1 if either a or b is NaN
|
|
//
|
|
// __gesf2(a,b) returns -1 if a < b
|
|
// 0 if a == b
|
|
// 1 if a > b
|
|
// -1 if either a or b is NaN
|
|
//
|
|
// __unordsf2(a,b) returns 0 if both a and b are numbers
|
|
// 1 if either a or b is NaN
|
|
//
|
|
// Note that __lesf2( ) and __gesf2( ) are identical except in their handling of
|
|
// NaN values.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "../assembly.h"
|
|
.syntax unified
|
|
|
|
.align 2
|
|
DEFINE_COMPILERRT_FUNCTION(__eqsf2)
|
|
DEFINE_COMPILERRT_FUNCTION(__lesf2)
|
|
DEFINE_COMPILERRT_FUNCTION(__ltsf2)
|
|
DEFINE_COMPILERRT_FUNCTION(__nesf2)
|
|
// Make copies of a and b with the sign bit shifted off the top. These will
|
|
// be used to detect zeros and NaNs.
|
|
mov r2, r0, lsl #1
|
|
mov r3, r1, lsl #1
|
|
|
|
// We do the comparison in three stages (ignoring NaN values for the time
|
|
// being). First, we orr the absolute values of a and b; this sets the Z
|
|
// flag if both a and b are zero (of either sign). The shift of r3 doesn't
|
|
// effect this at all, but it *does* make sure that the C flag is clear for
|
|
// the subsequent operations.
|
|
orrs r12, r2, r3, lsr #1
|
|
|
|
// Next, we check if a and b have the same or different signs. If they have
|
|
// opposite signs, this eor will set the N flag.
|
|
eorsne r12, r0, r1
|
|
|
|
// If a and b are equal (either both zeros or bit identical; again, we're
|
|
// ignoring NaNs for now), this subtract will zero out r0. If they have the
|
|
// same sign, the flags are updated as they would be for a comparison of the
|
|
// absolute values of a and b.
|
|
subspl r0, r2, r3
|
|
|
|
// If a is smaller in magnitude than b and both have the same sign, place
|
|
// the negation of the sign of b in r0. Thus, if both are negative and
|
|
// a > b, this sets r0 to 0; if both are positive and a < b, this sets
|
|
// r0 to -1.
|
|
//
|
|
// This is also done if a and b have opposite signs and are not both zero,
|
|
// because in that case the subtract was not performed and the C flag is
|
|
// still clear from the shift argument in orrs; if a is positive and b
|
|
// negative, this places 0 in r0; if a is negative and b positive, -1 is
|
|
// placed in r0.
|
|
mvnlo r0, r1, asr #31
|
|
|
|
// If a is greater in magnitude than b and both have the same sign, place
|
|
// the sign of b in r0. Thus, if both are negative and a < b, -1 is placed
|
|
// in r0, which is the desired result. Conversely, if both are positive
|
|
// and a > b, zero is placed in r0.
|
|
movhi r0, r1, asr #31
|
|
|
|
// If you've been keeping track, at this point r0 contains -1 if a < b and
|
|
// 0 if a >= b. All that remains to be done is to set it to 1 if a > b.
|
|
// If a == b, then the Z flag is set, so we can get the correct final value
|
|
// into r0 by simply or'ing with 1 if Z is clear.
|
|
orrne r0, r0, #1
|
|
|
|
// Finally, we need to deal with NaNs. If either argument is NaN, replace
|
|
// the value in r0 with 1.
|
|
cmp r2, #0xff000000
|
|
cmpls r3, #0xff000000
|
|
movhi r0, #1
|
|
bx lr
|
|
|
|
.align 2
|
|
DEFINE_COMPILERRT_FUNCTION(__gesf2)
|
|
DEFINE_COMPILERRT_FUNCTION(__gtsf2)
|
|
// Identical to the preceeding except in that we return -1 for NaN values.
|
|
// Given that the two paths share so much code, one might be tempted to
|
|
// unify them; however, the extra code needed to do so makes the code size
|
|
// to performance tradeoff very hard to justify for such small functions.
|
|
mov r2, r0, lsl #1
|
|
mov r3, r1, lsl #1
|
|
orrs r12, r2, r3, lsr #1
|
|
eorsne r12, r0, r1
|
|
subspl r0, r2, r3
|
|
mvnlo r0, r1, asr #31
|
|
movhi r0, r1, asr #31
|
|
orrne r0, r0, #1
|
|
cmp r2, #0xff000000
|
|
cmpls r3, #0xff000000
|
|
movhi r0, #-1
|
|
bx lr
|
|
|
|
.align 2
|
|
DEFINE_COMPILERRT_FUNCTION(__unordsf2)
|
|
// Return 1 for NaN values, 0 otherwise.
|
|
mov r2, r0, lsl #1
|
|
mov r3, r1, lsl #1
|
|
mov r0, #0
|
|
cmp r2, #0xff000000
|
|
cmpls r3, #0xff000000
|
|
movhi r0, #1
|
|
bx lr
|