Message ID | ZeX7n7+lvs5TzGk4@tucnak |
---|---|
State | New |
Headers | show |
Series | combine: Fix recent WORD_REGISTER_OPERATIONS check [PR113010] | expand |
On 3/4/24 09:49, Jakub Jelinek wrote: > On Mon, Mar 04, 2024 at 05:18:39PM +0100, Rainer Orth wrote: >>> On 2/26/24 17:17, Greg McGary wrote: >>>> The sign-bit-copies of a sign-extending load cannot be known until runtime on >>>> WORD_REGISTER_OPERATIONS targets, except in the case of a zero-extending MEM >>>> load. See the fix for PR112758. >>>> 2024-02-22 Greg McGary <gkm@rivosinc.com> >>>> PR rtl-optimization/113010 >>>> * combine.cc (simplify_comparison): Simplify a SUBREG on >>>> WORD_REGISTER_OPERATIONS targets only if it is a zero-extending >>>> MEM load. >>>> * gcc.c-torture/execute/pr113010.c: New test. >>> I think this is fine for the trunk. I'll do some final testing on it >>> tomorrow. >> >> unfortunately, the patch broke Solaris/SPARC bootstrap >> (sparc-sun-solaris2.11): >> >> /vol/gcc/src/hg/master/local/gcc/combine.cc: In function 'rtx_code simplify_comparison(rtx_code, rtx_def**, rtx_def**)': >> /vol/gcc/src/hg/master/local/gcc/combine.cc:12101:25: error: '*(unsigned int*)((char*)&inner_mode + offsetof(scalar_int_mode, scalar_int_mode::m_mode))' may be used uninitialized [-Werror=maybe-uninitialized] >> 12101 | scalar_int_mode mode, inner_mode, tmode; >> | ^~~~~~~~~~ > > I don't see how it could ever work properly, inner_mode in that spot is > just uninitialized. > > I think we shouldn't worry about paradoxical subregs of non-scalar_int_mode > REGs/MEMs and for the scalar_int_mode ones should initialize inner_mode > before we use it. > Another option would be to use > maybe_lt (GET_MODE_PRECISION (GET_MODE (SUBREG_REG (op0))), BITS_PER_WORD) > and > load_extend_op (GET_MODE (SUBREG_REG (op0))) == ZERO_EXTEND, > or set machine_mode smode = GET_MODE (SUBREG_REG (op0)); and use it in > those two spots. > > 2024-03-04 Jakub Jelinek <jakub@redhat.com> > > PR rtl-optimization/113010 > * combine.cc (simplify_comparison): Guard the > WORD_REGISTER_OPERATIONS check on scalar_int_mode of SUBREG_REG > and initialize inner_mode. Egad. Sorry. OK for the trunk. Thanks for picking this up. Got distracted by an internal issue. jeff
--- gcc/combine.cc.jj 2024-03-04 10:01:21.054937316 +0100 +++ gcc/combine.cc 2024-03-04 17:40:51.556052647 +0100 @@ -12554,6 +12554,8 @@ simplify_comparison (enum rtx_code code, if (paradoxical_subreg_p (op0)) { if (WORD_REGISTER_OPERATIONS + && is_a <scalar_int_mode> (GET_MODE (SUBREG_REG (op0)), + &inner_mode) && GET_MODE_PRECISION (inner_mode) < BITS_PER_WORD /* On WORD_REGISTER_OPERATIONS targets the bits beyond sub_mode aren't considered undefined,