On Mon, Feb 5, 2024 at 9:06 AM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Mon, Feb 5, 2024 at 1:24 AM Roger Sayle <ro...@nextmovesoftware.com> wrote:
> >
> >
> > This patch fixes PR target/113690, an ICE-on-valid regression on x86_64
> > that exhibits with a specific combination of command line options. The
> > cause is that x86's scalar-to-vector pass converts a chain of instructions
> > from TImode to V1TImode, but fails to appropriately update the attached
> > REG_EQUAL note. Given that multiplication isn't supported in V1TImode,
> > the REG_NOTE handling code wasn't expecting to see a MULT. Easily solved
> > with additional handling for other binary operators that may potentially
> > (in future) have an immediate constant as the second operand that needs
> > handling. For convenience, this code (re)factors the logic to convert
> > a TImode constant into a V1TImode constant vector into a subroutine and
> > reuses it.
> >
> > For the record, STV is actually doing something useful in this strange
> > testcase, GCC with -O2 -fno-dce -fno-forward-propagate
> > -fno-split-wide-types
> > -funroll-loops generates:
> >
> > foo: movl $v, %eax
> > pxor %xmm0, %xmm0
> > movaps %xmm0, 48(%rax)
> > movaps %xmm0, (%rax)
> > movaps %xmm0, 16(%rax)
> > movaps %xmm0, 32(%rax)
> > ret
> >
> > With the addition of -mno-stv (to disable the patched code) it gives:
> >
> > foo: movl $v, %eax
> > movq $0, 48(%rax)
> > movq $0, 56(%rax)
> > movq $0, (%rax)
> > movq $0, 8(%rax)
> > movq $0, 16(%rax)
> > movq $0, 24(%rax)
> > movq $0, 32(%rax)
> > movq $0, 40(%rax)
> > ret
> >
> >
> > This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> > and make -k check, both with and without --target_board=unix{-m32}
> > with no new failures. Ok for mainline?
> >
> >
> > 2024-02-05 Roger Sayle <ro...@nextmovesoftware.com>
> >
> > gcc/ChangeLog
> > PR target/113690
> > * config/i386/i386-features.cc (timode_convert_cst): New helper
> > function to convert a TImode CONST_SCALAR_INT_P to a V1TImode
> > CONST_VECTOR.
> > (timode_scalar_chain::convert_op): Use timode_convert_cst.
> > (timode_scalar_chain::convert_insn): If a REG_EQUAL note contains
> > a binary operator where the second operand is an immediate integer
> > constant, convert it to V1TImode using timode_convert_cst.
> > Use timode_convert_cst.
> >
> > gcc/testsuite/ChangeLog
> > PR target/113690
> > * gcc.target/i386/pr113690.c: New test case.
>
> OK.
OTOH, how about we follow the approach from
general_scalar_chain::convert_insn and just kill the note?
Uros.
