From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by sourceware.org (Postfix) with ESMTPS id 99FD6385780E for ; Thu, 28 Oct 2021 12:40:26 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 99FD6385780E Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 82F341FD4F; Thu, 28 Oct 2021 12:40:25 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 5B6B313C5C; Thu, 28 Oct 2021 12:40:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id YqJ8FDmaemEUagAAMHmgww (envelope-from ); Thu, 28 Oct 2021 12:40:25 +0000 Date: Thu, 28 Oct 2021 14:40:24 +0200 (CEST) From: Richard Biener To: Jakub Jelinek cc: gcc-patches@gcc.gnu.org, joseph@codesourcery.com Subject: Re: [PATCH] middle-end/84407 - honor -frounding-math for int to float conversion In-Reply-To: <93s2o6ns-8r2-77r6-305s-q5283s47qr8@fhfr.qr> Message-ID: <398o51ss-2o1p-osrr-sr7n-r9n3sqp12ors@fhfr.qr> References: <2qq2o881-1r56-7ooq-37o7-70n599n773r8@fhfr.qr> <20211028115252.GP304296@tucnak> <93s2o6ns-8r2-77r6-305s-q5283s47qr8@fhfr.qr> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, LOTS_OF_MONEY, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Oct 2021 12:40:28 -0000 On Thu, 28 Oct 2021, Richard Biener wrote: > On Thu, 28 Oct 2021, Jakub Jelinek wrote: > > > On Thu, Oct 28, 2021 at 01:32:17PM +0200, Richard Biener wrote: > > > diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c > > > index f38b6d7d31c..a16395befcd 100644 > > > --- a/gcc/simplify-rtx.c > > > +++ b/gcc/simplify-rtx.c > > > @@ -1917,6 +1917,19 @@ simplify_const_unary_operation (enum rtx_code code, machine_mode mode, > > > return 0; > > > > > > d = real_value_truncate (mode, d); > > > + > > > + /* Avoid the folding if flag_rounding_math is on and the > > > + conversion is not exact. */ > > > + if (HONOR_SIGN_DEPENDENT_ROUNDING (mode)) > > > + { > > > + bool fail = false; > > > + wide_int w = real_to_integer (&d, &fail, > > > + GET_MODE_PRECISION > > > + (as_a (op_mode))); > > > + if (fail || wi::ne_p (w, wide_int (rtx_mode_t (op, op_mode)))) > > > + return 0; > > > + } > > > + > > > return const_double_from_real_value (d, mode); > > > } > > > else if (code == UNSIGNED_FLOAT && CONST_SCALAR_INT_P (op)) > > > > What about the else if case (i.e. UNSIGNED_FLOAT)? > > I'm not able to trigger unsigned_float to be used, even when > converting 0x8000000000000001 I get (float:DF (reg:DI...)) > on x86_64 because we emit conditional code that will end up > using some compensation to emulate unsigned_float with > float with some tricks that do not necessarily look safe > from a rounding perspective (so maybe x86 would need to > resort to soft-fp here?): > > movabsq $4611686018427387905, %rax > cvtsi2sdq %rax, %xmm0 > addsd %xmm0, %xmm0 > ucomisd .LC0(%rip), %xmm0 > > the constant is (0x8000000000000001u >> 1) | 1 > > > And I think it would be nice to test the simplify-rtx.c code somewhere, > > perhaps gcc/testsuite/gcc.dg/rtl/x86_64 testcase and check that we > > simplify with -frounding-math e.g. UNSIGNED_FLOAT from DImode > > 0x8000000000000000 or FLOAT or UNSIGNED_FLOAT from DImode > > 0x7ffffffffffffc00, but will not fold FLOAT or UNSIGNED_FLOAT from > > DImode 0x7ffffffffffffc01 or 0x7fffffffffffffff. > > That it is not folded is exercised by the testcase already. I indeed > have no good way to test actual folding besides an RTL testcase > (and I didn't add one for GIMPLE). > > But as said elsehwere I don't see the RTL constant folding code > as important with regard to floats, but of course we have to fix it up. > > The patch as-is fixes the reported testcase on x86_64, a target > eventually not implementing float but only unsigned_float might be > still broken. I can put the same code in the unsigned_float code > but I have no way of exercising it. > > Anyway, it feels like I spent too much time on this already for what > was supposed to be low-hanging fruit ;) The following nevertheless adds a testcase with large enough constants that might trigger unsigned_float plus a hunk to fix that. Would that be OK? Thanks, Richard. >From bb57eaf45329e1dd0ccb0fe82b30e189d1cd86a4 Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Thu, 28 Oct 2021 11:38:32 +0200 Subject: [PATCH] middle-end/84407 - honor -frounding-math for int to float conversion To: gcc-patches@gcc.gnu.org This makes us honor -frounding-math for integer to float conversions and avoid constant folding when such conversion is not exact. 2021-10-28 Richard Biener PR middle-end/84407 * fold-const.c (fold_convert_const): Avoid int to float constant folding with -frounding-math and inexact result. * simplify-rtx.c (simplify_const_unary_operation): Likewise for both float and unsigned_float. * gcc.dg/torture/fp-uint64-convert-double-1.c: New testcase. * gcc.dg/torture/fp-uint64-convert-double-2.c: Likewise. --- gcc/fold-const.c | 15 +++- gcc/simplify-rtx.c | 26 +++++++ .../torture/fp-uint64-convert-double-1.c | 74 ++++++++++++++++++ .../torture/fp-uint64-convert-double-2.c | 75 +++++++++++++++++++ 4 files changed, 189 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-1.c create mode 100644 gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-2.c diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 18950aeb760..c7daf871125 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -2290,7 +2290,20 @@ fold_convert_const (enum tree_code code, tree type, tree arg1) else if (TREE_CODE (type) == REAL_TYPE) { if (TREE_CODE (arg1) == INTEGER_CST) - return build_real_from_int_cst (type, arg1); + { + tree res = build_real_from_int_cst (type, arg1); + /* Avoid the folding if flag_rounding_math is on and the + conversion is not exact. */ + if (HONOR_SIGN_DEPENDENT_ROUNDING (type)) + { + bool fail = false; + wide_int w = real_to_integer (&TREE_REAL_CST (res), &fail, + TYPE_PRECISION (TREE_TYPE (arg1))); + if (fail || wi::ne_p (w, wi::to_wide (arg1))) + return NULL_TREE; + } + return res; + } else if (TREE_CODE (arg1) == REAL_CST) return fold_convert_const_real_from_real (type, arg1); else if (TREE_CODE (arg1) == FIXED_CST) diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index f38b6d7d31c..a060f1bbce0 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -1917,6 +1917,19 @@ simplify_const_unary_operation (enum rtx_code code, machine_mode mode, return 0; d = real_value_truncate (mode, d); + + /* Avoid the folding if flag_rounding_math is on and the + conversion is not exact. */ + if (HONOR_SIGN_DEPENDENT_ROUNDING (mode)) + { + bool fail = false; + wide_int w = real_to_integer (&d, &fail, + GET_MODE_PRECISION + (as_a (op_mode))); + if (fail || wi::ne_p (w, wide_int (rtx_mode_t (op, op_mode)))) + return 0; + } + return const_double_from_real_value (d, mode); } else if (code == UNSIGNED_FLOAT && CONST_SCALAR_INT_P (op)) @@ -1941,6 +1954,19 @@ simplify_const_unary_operation (enum rtx_code code, machine_mode mode, return 0; d = real_value_truncate (mode, d); + + /* Avoid the folding if flag_rounding_math is on and the + conversion is not exact. */ + if (HONOR_SIGN_DEPENDENT_ROUNDING (mode)) + { + bool fail = false; + wide_int w = real_to_integer (&d, &fail, + GET_MODE_PRECISION + (as_a (op_mode))); + if (fail || wi::ne_p (w, wide_int (rtx_mode_t (op, op_mode)))) + return 0; + } + return const_double_from_real_value (d, mode); } diff --git a/gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-1.c b/gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-1.c new file mode 100644 index 00000000000..b40a16a2257 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-1.c @@ -0,0 +1,74 @@ +/* PR84407 */ +/* { dg-do run } */ +/* { dg-require-effective-target fenv } */ +/* { dg-additional-options "-frounding-math" } */ + +#include +#include + +void __attribute__((noipa)) +fooa () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_TONEAREST + fesetround(FE_TONEAREST); + __UINT64_TYPE__ x = 0x7fffffffffffffff; + double f = x; + if (f != 0x1p+63) + abort (); +#endif +#endif +} + +void __attribute__((noipa)) +foob () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_DOWNWARD + fesetround(FE_DOWNWARD); + __UINT64_TYPE__ x = 0x7fffffffffffffff; + double f = x; + if (f != 0x1.fffffffffffffp+62) + abort (); +#endif +#endif +} + +void __attribute__((noipa)) +fooc () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_UPWARD + fesetround(FE_UPWARD); + __UINT64_TYPE__ x = 0x7fffffffffffffff; + double f = x; + if (f != 0x1p+63) + abort (); +#endif +#endif +} + +void __attribute__((noipa)) +food () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_TOWARDZERO + fesetround(FE_TOWARDZERO); + __UINT64_TYPE__ x = 0x7fffffffffffffff; + double f = x; + if (f != 0x1.fffffffffffffp+62) + abort (); +#endif +#endif +} + + +int +main () +{ + fooa (); + foob (); + fooc (); + food (); + return 0; +} diff --git a/gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-2.c b/gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-2.c new file mode 100644 index 00000000000..952f96b33c9 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/fp-uint64-convert-double-2.c @@ -0,0 +1,75 @@ +/* PR84407 */ +/* { dg-do run } */ +/* { dg-require-effective-target fenv } */ +/* { dg-additional-options "-frounding-math" } */ + +#include +#include + +void __attribute__((noipa)) +fooa () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_TONEAREST + fesetround(FE_TONEAREST); + /* Large enough constant to trigger unsigned_float. */ + __UINT64_TYPE__ x = 0x8000000000000001; + double f = x; + if (f != 0x1p+63) + abort (); +#endif +#endif +} + +void __attribute__((noipa)) +foob () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_DOWNWARD + fesetround(FE_DOWNWARD); + __UINT64_TYPE__ x = 0x8000000000000001; + double f = x; + if (f != 0x1p+63) + abort (); +#endif +#endif +} + +void __attribute__((noipa)) +fooc () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_UPWARD + fesetround(FE_UPWARD); + __UINT64_TYPE__ x = 0x8000000000000001; + double f = x; + if (f != 0x1.0000000000001p+63) + abort (); +#endif +#endif +} + +void __attribute__((noipa)) +food () +{ +#if __DBL_MANT_DIG__ == 53 +#ifdef FE_TOWARDZERO + fesetround(FE_TOWARDZERO); + __UINT64_TYPE__ x = 0x8000000000000001; + double f = x; + if (f != 0x1p+63) + abort (); +#endif +#endif +} + + +int +main () +{ + fooa (); + foob (); + fooc (); + food (); + return 0; +} -- 2.31.1