On October 4, 2021 7:00:10 PM GMT+02:00, Qing Zhao <qing.z...@oracle.com> wrote: >I have several questions on this fix: > >1. This fix avoided expanding “.DEFERRED_INIT” when !tree_fits_uhwi_p >(TYPE_SIZE_UNIT (var_type)). > As a result, this call to .DEFERRED_INIT will NOT be expanded at all.
Yes. > Then not expanding .DEFERRED_INIT in RTL expanding phase will trigger more > issues in later RTL phases, this looks not correct to me. (Actually, with is > the patch, this testing case still failed in a later RTL stage). > > So, If we really want to avoid auto-init for VLA vectors, we should not > add call to .DEFERRED_INIT in gimplification phase at all. > > >2. For the added .DEFERRED_INIT: > > __SVFloat64_t f64; > > f64 = .DEFERRED_INIT (POLY_INT_CST [16, 16], 2, 0); > >What does “POLY_INT_CST[16,16]” mean? Is this a constant size? If YES, what’s >the value of it? If Not, can we use “memset” to expand it? When the target is a register memset doesn't work. I'm not sure the memset expansion path will work as-is either for aggregates with vla parts - but I'll leave that to Richard S. to sort out. Richard. >Thanks. > >Qing > > > >> On Oct 4, 2021, at 3:57 AM, Richard Biener via Gcc-patches >> <gcc-patches@gcc.gnu.org> wrote: >> >> This avoids ICEing for VLA vector auto-init by not initializing. >> >> Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed. >> >> 2021-10-04 Richard Biener <rguent...@suse.de> >> >> PR middle-end/102587 >> * internal-fn.c (expand_DEFERRED_INIT): Guard register >> initialization path an avoid initializing VLA registers >> with it. >> >> * gcc.target/aarch64/sve/pr102587-1.c: New testcase. >> * gcc.target/aarch64/sve/pr102587-2.c: Likewise. >> --- >> gcc/internal-fn.c | 3 ++- >> gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c | 4 ++++ >> gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c | 4 ++++ >> 3 files changed, 10 insertions(+), 1 deletion(-) >> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c >> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c >> >> diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c >> index 8312d08aab2..ef5dc90db56 100644 >> --- a/gcc/internal-fn.c >> +++ b/gcc/internal-fn.c >> @@ -3035,7 +3035,8 @@ expand_DEFERRED_INIT (internal_fn, gcall *stmt) >> /* Expand this memset call. */ >> expand_builtin_memset (m_call, NULL_RTX, TYPE_MODE (var_type)); >> } >> - else >> + /* ??? Deal with poly-int sized registers. */ >> + else if (tree_fits_uhwi_p (TYPE_SIZE_UNIT (var_type))) >> { >> /* If this variable is in a register, use expand_assignment might >> generate better code. */ >> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c >> b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c >> new file mode 100644 >> index 00000000000..2b9a68b0b59 >> --- /dev/null >> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c >> @@ -0,0 +1,4 @@ >> +/* { dg-do compile } */ >> +/* { dg-options "-ftrivial-auto-var-init=zero" } */ >> + >> +void foo() { __SVFloat64_t f64; } >> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c >> b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c >> new file mode 100644 >> index 00000000000..4cdb9056002 >> --- /dev/null >> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c >> @@ -0,0 +1,4 @@ >> +/* { dg-do compile } */ >> +/* { dg-options "-ftrivial-auto-var-init=pattern" } */ >> + >> +void foo() { __SVFloat64_t f64; } >> -- >> 2.31.1 >