From: Eric Blake <eblake@redhat.com>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"David Hildenbrand" <david@redhat.com>,
"Richard W.M. Jones" <rjones@redhat.com>,
"Richard Henderson" <richard.henderson@linaro.org>
Cc: qemu-devel@nongnu.org
Subject: Re: [PULL 11/24] tcg/optimize: Use tcg_constant_internal with constant folding
Date: Thu, 4 Feb 2021 10:52:02 -0600 [thread overview]
Message-ID: <2d75544e-a325-aa1a-6b01-ecdd41eb64bf@redhat.com> (raw)
In-Reply-To: <e1bc591d-009f-3b0f-83a0-36095efff7ee@amsat.org>
On 2/4/21 10:04 AM, Philippe Mathieu-Daudé wrote:
>>> Isn't it kind of weird that this would only affect an s390 host? I
>>> don't understand why the host would make a difference if we're doing
>>> TCG.
>>
>> I assume an existing BUG in the s390x TCG backend ... which makes it
>> harder to debug :)
>
> This seems to fix it:
>
> -- >8 --
> diff --git a/tcg/s390/tcg-target.c.inc b/tcg/s390/tcg-target.c.inc
> index 8517e552323..32d03dbfbaf 100644
> --- a/tcg/s390/tcg-target.c.inc
> +++ b/tcg/s390/tcg-target.c.inc
> @@ -1094,10 +1094,16 @@ static int tgen_cmp(TCGContext *s, TCGType type,
> TCGCond c, TCGReg r1,
> op = (is_unsigned ? RIL_CLFI : RIL_CFI);
> tcg_out_insn_RIL(s, op, r1, c2);
> goto exit;
> - } else if (c2 == (is_unsigned ? (uint32_t)c2 : (int32_t)c2)) {
In this code, you are comparing c2 to the type promotion of uint32_t and
int32_t. That is, the conversion rules are as if you had done:
(common_type) c2 == (common_type) (uint32_t) (is_unsigned ? (uint32_t)c2
: (uint32_t)(int32_t)c2)
> - op = (is_unsigned ? RIL_CLGFI : RIL_CGFI);
> - tcg_out_insn_RIL(s, op, r1, c2);
> - goto exit;
> + } else if (is_unsigned) {
> + if (c2 == (uint32_t)c2) {
whereas this is:
(common_type_unsigned)c2 == (common_type_unsigned)(uint32_t)c2
> + tcg_out_insn_RIL(s, RIL_CLGFI, r1, c2);
> + goto exit;
> + }
> + } else {
> + if (c2 == (int32_t)c2) {
and this is:
(common_type_signed)c2 == (common_type_signed)(int32_t)c2
and the two may indeed use a different type.
I'm not sure (from the context shown here) what the type of c2 was, to
determine what the common types are, but as an example, on my 64-bit system,
(long)-1 == (int32_t)-1
is true (the 64-bit value (long)-1 is equal to the sign-extended 64-bit
value created from the signed 32-bit value (int32_t)-1), while
(unsigned long)-1 == (uint32_t)(int32_t)-1
is false (the 32-bit unsigned value (uint32_t) -1 promotes without sign
extension to the 64-bit (unsigned long) type, and 0xffffffffffffffff is
not equal to 0x00000000ffffffff).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2021-02-04 17:25 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 2:16 [PULL 00/24] tcg patch queue Richard Henderson
2021-01-14 2:16 ` [PULL 01/24] tcg: Use tcg_out_dupi_vec from temp_load Richard Henderson
2021-01-14 2:16 ` [PULL 02/24] tcg: Increase tcg_out_dupi_vec immediate to int64_t Richard Henderson
2021-01-14 2:16 ` [PULL 03/24] tcg: Consolidate 3 bits into enum TCGTempKind Richard Henderson
2021-01-14 2:16 ` [PULL 04/24] tcg: Add temp_readonly Richard Henderson
2021-01-14 2:16 ` [PULL 05/24] tcg: Expand TCGTemp.val to 64-bits Richard Henderson
2021-01-14 2:16 ` [PULL 06/24] tcg: Rename struct tcg_temp_info to TempOptInfo Richard Henderson
2021-01-14 2:16 ` [PULL 07/24] tcg: Expand TempOptInfo to 64-bits Richard Henderson
2021-01-14 2:16 ` [PULL 08/24] tcg: Introduce TYPE_CONST temporaries Richard Henderson
2021-01-14 2:16 ` [PULL 09/24] tcg/optimize: Improve find_better_copy Richard Henderson
2021-01-14 2:16 ` [PULL 10/24] tcg/optimize: Adjust TempOptInfo allocation Richard Henderson
2021-01-14 2:16 ` [PULL 11/24] tcg/optimize: Use tcg_constant_internal with constant folding Richard Henderson
2021-01-15 23:03 ` Alistair Francis
2021-01-16 17:24 ` Richard Henderson
2021-01-18 20:17 ` Laurent Vivier
2021-01-18 21:03 ` Richard Henderson
2021-02-01 20:45 ` Richard W.M. Jones
2021-02-01 20:53 ` Richard W.M. Jones
2021-02-04 2:22 ` Richard Henderson
2021-02-04 6:41 ` David Hildenbrand
2021-02-04 7:55 ` David Hildenbrand
2021-02-04 8:38 ` David Hildenbrand
2021-02-04 9:03 ` Richard W.M. Jones
2021-02-04 9:12 ` David Hildenbrand
2021-02-04 9:29 ` Richard W.M. Jones
2021-02-04 9:30 ` Richard W.M. Jones
2021-02-04 9:37 ` David Hildenbrand
2021-02-04 16:04 ` Philippe Mathieu-Daudé
2021-02-04 16:08 ` Philippe Mathieu-Daudé
2021-02-04 16:12 ` David Hildenbrand
2021-02-04 16:29 ` David Hildenbrand
2021-02-04 16:57 ` Eric Blake
2021-02-04 17:33 ` Richard Henderson
2021-02-04 16:48 ` Richard W.M. Jones
2021-02-04 16:52 ` Eric Blake [this message]
2021-01-14 2:16 ` [PULL 12/24] tcg: Convert tcg_gen_dupi_vec to TCG_CONST Richard Henderson
2021-01-14 2:16 ` [PULL 13/24] tcg: Use tcg_constant_i32 with icount expander Richard Henderson
2021-01-14 2:16 ` [PULL 14/24] tcg: Use tcg_constant_{i32,i64} with tcg int expanders Richard Henderson
2021-02-10 10:38 ` Alex Bennée
2021-01-14 2:16 ` [PULL 15/24] tcg: Use tcg_constant_{i32,i64} with tcg plugins Richard Henderson
2021-01-14 2:16 ` [PULL 16/24] tcg: Use tcg_constant_{i32,i64,vec} with gvec expanders Richard Henderson
2021-01-14 2:16 ` [PULL 17/24] tcg/tci: Add special tci_movi_{i32,i64} opcodes Richard Henderson
2021-01-14 2:16 ` [PULL 18/24] tcg: Remove movi and dupi opcodes Richard Henderson
2021-01-14 2:16 ` [PULL 19/24] tcg: Add tcg_reg_alloc_dup2 Richard Henderson
2021-01-14 2:16 ` [PULL 20/24] tcg/i386: Use tcg_constant_vec with tcg vec expanders Richard Henderson
2021-01-14 2:16 ` [PULL 21/24] tcg: Remove tcg_gen_dup{8,16,32,64}i_vec Richard Henderson
2021-01-14 2:16 ` [PULL 22/24] tcg/ppc: Use tcg_constant_vec with tcg vec expanders Richard Henderson
2021-01-14 2:16 ` [PULL 23/24] tcg/aarch64: " Richard Henderson
2021-01-14 2:16 ` [PULL 24/24] decodetree: Open files with encoding='utf-8' Richard Henderson
2021-01-14 13:13 ` [PULL 00/24] tcg patch queue Peter Maydell
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