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re PR target/43703 (Unexpected floating point precision loss due to ARM NEON autovectorization)

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2010-07-02  Julian Brown  <julian@codesourcery.com>
	    Sandra Loosemore <sandra@codesourcery.com>

	PR target/43703

	gcc/
	* config/arm/vec-common.md (add<mode>3, sub<mode>3, smin<mode>3)
	(smax<mode>3): Disable for NEON float modes when
	flag_unsafe_math_optimizations is false.
	* config/arm/neon.md (*add<mode>3_neon, *sub<mode>3_neon)
	(*mul<mode>3_neon)
	(mul<mode>3add<mode>_neon, mul<mode>3neg<mode>add<mode>_neon)
	(reduc_splus_<mode>, reduc_smin_<mode>, reduc_smax_<mode>): Disable
	for NEON float modes when flag_unsafe_math_optimizations is false.
	(quad_halves_<code>v4sf): Only enable if flag_unsafe_math_optimizations
	is true.
	* doc/invoke.texi (ARM Options): Add note about floating point
	vectorization requiring -funsafe-math-optimizations.

	gcc/testsuite/
	* gcc.dg/vect/vect.exp: Add -ffast-math for NEON.
	* gcc.dg/vect/vect-reduc-6.c: Add XFAIL for NEON.



Co-Authored-By: Sandra Loosemore <sandra@codesourcery.com>

From-SVN: r161763
This commit is contained in:
Julian Brown 2010-07-03 00:46:51 +00:00 committed by Sandra Loosemore
parent bab53516d0
commit 400cfcf50e
7 changed files with 63 additions and 18 deletions
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18
gcc/ChangeLog
View File

@ -1,3 +1,21 @@
2010-07-02 Julian Brown <julian@codesourcery.com>
Sandra Loosemore <sandra@codesourcery.com>
PR target/43703
* config/arm/vec-common.md (add<mode>3, sub<mode>3, smin<mode>3)
(smax<mode>3): Disable for NEON float modes when
flag_unsafe_math_optimizations is false.
* config/arm/neon.md (*add<mode>3_neon, *sub<mode>3_neon)
(*mul<mode>3_neon)
(mul<mode>3add<mode>_neon, mul<mode>3neg<mode>add<mode>_neon)
(reduc_splus_<mode>, reduc_smin_<mode>, reduc_smax_<mode>): Disable
for NEON float modes when flag_unsafe_math_optimizations is false.
(quad_halves_<code>v4sf): Only enable if flag_unsafe_math_optimizations
is true.
* doc/invoke.texi (ARM Options): Add note about floating point
vectorization requiring -funsafe-math-optimizations.
2010-07-02 Sandra Loosemore <sandra@codesourcery.com>
Julian Brown <julian@codesourcery.com>

24
gcc/config/arm/neon.md
View File

@ -819,7 +819,7 @@
[(set (match_operand:VDQ 0 "s_register_operand" "=w")
(plus:VDQ (match_operand:VDQ 1 "s_register_operand" "w")
(match_operand:VDQ 2 "s_register_operand" "w")))]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
"vadd.<V_if_elem>\t%<V_reg>0, %<V_reg>1, %<V_reg>2"
[(set (attr "neon_type")
(if_then_else (ne (symbol_ref "<Is_float_mode>") (const_int 0))
@ -853,7 +853,7 @@
[(set (match_operand:VDQ 0 "s_register_operand" "=w")
(minus:VDQ (match_operand:VDQ 1 "s_register_operand" "w")
(match_operand:VDQ 2 "s_register_operand" "w")))]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
"vsub.<V_if_elem>\t%<V_reg>0, %<V_reg>1, %<V_reg>2"
[(set (attr "neon_type")
(if_then_else (ne (symbol_ref "<Is_float_mode>") (const_int 0))
@ -888,7 +888,7 @@
[(set (match_operand:VDQ 0 "s_register_operand" "=w")
(mult:VDQ (match_operand:VDQ 1 "s_register_operand" "w")
(match_operand:VDQ 2 "s_register_operand" "w")))]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
"vmul.<V_if_elem>\t%<V_reg>0, %<V_reg>1, %<V_reg>2"
[(set (attr "neon_type")
(if_then_else (ne (symbol_ref "<Is_float_mode>") (const_int 0))
@ -910,7 +910,7 @@
(plus:VDQ (mult:VDQ (match_operand:VDQ 2 "s_register_operand" "w")
(match_operand:VDQ 3 "s_register_operand" "w"))
(match_operand:VDQ 1 "s_register_operand" "0")))]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
"vmla.<V_if_elem>\t%<V_reg>0, %<V_reg>2, %<V_reg>3"
[(set (attr "neon_type")
(if_then_else (ne (symbol_ref "<Is_float_mode>") (const_int 0))
@ -932,7 +932,7 @@
(minus:VDQ (match_operand:VDQ 1 "s_register_operand" "0")
(mult:VDQ (match_operand:VDQ 2 "s_register_operand" "w")
(match_operand:VDQ 3 "s_register_operand" "w"))))]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
"vmls.<V_if_elem>\t%<V_reg>0, %<V_reg>2, %<V_reg>3"
[(set (attr "neon_type")
(if_then_else (ne (symbol_ref "<Is_float_mode>") (const_int 0))
@ -1361,7 +1361,7 @@
(parallel [(const_int 0) (const_int 1)]))
(vec_select:V2SF (match_dup 1)
(parallel [(const_int 2) (const_int 3)]))))]
"TARGET_NEON"
"TARGET_NEON && flag_unsafe_math_optimizations"
"<VQH_mnem>.f32\t%P0, %e1, %f1"
[(set_attr "vqh_mnem" "<VQH_mnem>")
(set (attr "neon_type")
@ -1496,7 +1496,7 @@
(define_expand "reduc_splus_<mode>"
[(match_operand:VD 0 "s_register_operand" "")
(match_operand:VD 1 "s_register_operand" "")]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
{
neon_pairwise_reduce (operands[0], operands[1], <MODE>mode,
&gen_neon_vpadd_internal<mode>);
@ -1506,7 +1506,7 @@
(define_expand "reduc_splus_<mode>"
[(match_operand:VQ 0 "s_register_operand" "")
(match_operand:VQ 1 "s_register_operand" "")]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
{
rtx step1 = gen_reg_rtx (<V_HALF>mode);
rtx res_d = gen_reg_rtx (<V_HALF>mode);
@ -1541,7 +1541,7 @@
(define_expand "reduc_smin_<mode>"
[(match_operand:VD 0 "s_register_operand" "")
(match_operand:VD 1 "s_register_operand" "")]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
{
neon_pairwise_reduce (operands[0], operands[1], <MODE>mode,
&gen_neon_vpsmin<mode>);
@ -1551,7 +1551,7 @@
(define_expand "reduc_smin_<mode>"
[(match_operand:VQ 0 "s_register_operand" "")
(match_operand:VQ 1 "s_register_operand" "")]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
{
rtx step1 = gen_reg_rtx (<V_HALF>mode);
rtx res_d = gen_reg_rtx (<V_HALF>mode);
@ -1566,7 +1566,7 @@
(define_expand "reduc_smax_<mode>"
[(match_operand:VD 0 "s_register_operand" "")
(match_operand:VD 1 "s_register_operand" "")]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
{
neon_pairwise_reduce (operands[0], operands[1], <MODE>mode,
&gen_neon_vpsmax<mode>);
@ -1576,7 +1576,7 @@
(define_expand "reduc_smax_<mode>"
[(match_operand:VQ 0 "s_register_operand" "")
(match_operand:VQ 1 "s_register_operand" "")]
"TARGET_NEON"
"TARGET_NEON && (!<Is_float_mode> || flag_unsafe_math_optimizations)"
{
rtx step1 = gen_reg_rtx (<V_HALF>mode);
rtx res_d = gen_reg_rtx (<V_HALF>mode);

16
gcc/config/arm/vec-common.md
View File

@ -57,7 +57,8 @@
[(set (match_operand:VALL 0 "s_register_operand" "")
(plus:VALL (match_operand:VALL 1 "s_register_operand" "")
(match_operand:VALL 2 "s_register_operand" "")))]
"TARGET_NEON
"(TARGET_NEON && ((<MODE>mode != V2SFmode && <MODE>mode != V4SFmode)
|| flag_unsafe_math_optimizations))
|| (TARGET_REALLY_IWMMXT && VALID_IWMMXT_REG_MODE (<MODE>mode))"
{
})
@ -66,7 +67,8 @@
[(set (match_operand:VALL 0 "s_register_operand" "")
(minus:VALL (match_operand:VALL 1 "s_register_operand" "")
(match_operand:VALL 2 "s_register_operand" "")))]
"TARGET_NEON
"(TARGET_NEON && ((<MODE>mode != V2SFmode && <MODE>mode != V4SFmode)
|| flag_unsafe_math_optimizations))
|| (TARGET_REALLY_IWMMXT && VALID_IWMMXT_REG_MODE (<MODE>mode))"
{
})
@ -75,7 +77,9 @@
[(set (match_operand:VALLW 0 "s_register_operand" "")
(mult:VALLW (match_operand:VALLW 1 "s_register_operand" "")
(match_operand:VALLW 2 "s_register_operand" "")))]
"TARGET_NEON || (<MODE>mode == V4HImode && TARGET_REALLY_IWMMXT)"
"(TARGET_NEON && ((<MODE>mode != V2SFmode && <MODE>mode != V4SFmode)
|| flag_unsafe_math_optimizations))
|| (<MODE>mode == V4HImode && TARGET_REALLY_IWMMXT)"
{
})
@ -83,7 +87,8 @@
[(set (match_operand:VALLW 0 "s_register_operand" "")
(smin:VALLW (match_operand:VALLW 1 "s_register_operand" "")
(match_operand:VALLW 2 "s_register_operand" "")))]
"TARGET_NEON
"(TARGET_NEON && ((<MODE>mode != V2SFmode && <MODE>mode != V4SFmode)
|| flag_unsafe_math_optimizations))
|| (TARGET_REALLY_IWMMXT && VALID_IWMMXT_REG_MODE (<MODE>mode))"
{
})
@ -101,7 +106,8 @@
[(set (match_operand:VALLW 0 "s_register_operand" "")
(smax:VALLW (match_operand:VALLW 1 "s_register_operand" "")
(match_operand:VALLW 2 "s_register_operand" "")))]
"TARGET_NEON
"(TARGET_NEON && ((<MODE>mode != V2SFmode && <MODE>mode != V4SFmode)
|| flag_unsafe_math_optimizations))
|| (TARGET_REALLY_IWMMXT && VALID_IWMMXT_REG_MODE (<MODE>mode))"
{
})

8
gcc/doc/invoke.texi
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@ -9976,6 +9976,14 @@ of GCC@.
If @option{-msoft-float} is specified this specifies the format of
floating point values.
If the selected floating-point hardware includes the NEON extension
(e.g. @option{-mfpu}=@samp{neon}), note that floating-point
operations will not be used by GCC's auto-vectorization pass unless
@option{-funsafe-math-optimizations} is also specified. This is
because NEON hardware does not fully implement the IEEE 754 standard for
floating-point arithmetic (in particular denormal values are treated as
zero), so the use of NEON instructions may lead to a loss of precision.
@item -mfp16-format=@var{name}
@opindex mfp16-format
Specify the format of the @code{__fp16} half-precision floating-point type.

8
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,11 @@
2010-07-02 Julian Brown <julian@codesourcery.com>
Sandra Loosemore <sandra@codesourcery.com>
PR target/43703
* gcc.dg/vect/vect.exp: Add -ffast-math for NEON.
* gcc.dg/vect/vect-reduc-6.c: Add XFAIL for NEON.
2010-07-02 Sandra Loosemore <sandra@codesourcery.com>
Julian Brown <julian@codesourcery.com>

3
gcc/testsuite/gcc.dg/vect/vect-reduc-6.c
View File

@ -49,5 +49,6 @@ int main (void)
}
/* need -ffast-math to vectorizer these loops. */
/* { dg-final { scan-tree-dump-times "vectorized 0 loops" 1 "vect" } } */
/* ARM NEON passes -ffast-math to these tests, so expect this to fail. */
/* { dg-final { scan-tree-dump-times "vectorized 0 loops" 1 "vect" { xfail arm_neon_ok } } } */
/* { dg-final { cleanup-tree-dump "vect" } } */

4
gcc/testsuite/gcc.dg/vect/vect.exp
View File

@ -105,6 +105,10 @@ if [istarget "powerpc-*paired*"] {
set dg-do-what-default run
} elseif [is-effective-target arm_neon_ok] {
eval lappend DEFAULT_VECTCFLAGS [add_options_for_arm_neon ""]
# NEON does not support denormals, so is not used for vectorization by
# default to avoid loss of precision. We must pass -ffast-math to test
# vectorization of float operations.
lappend DEFAULT_VECTCFLAGS "-ffast-math"
if [is-effective-target arm_neon_hw] {
set dg-do-what-default run
} else {