Hi!
On Tue, Jul 01, 2025 at 05:16:45PM +0200, Jakub Jelinek wrote:
> This test seems to fail when testing with
> RUNTESTFLAGS="--target_board=unix/'{,-fstack-protector-strong}'"
> on power10.
Please mention near the start of the commit message (like, in the
subject already!) that the testcase did UB, and this patch fixes it?
> In my reading of the test and the instructions emitted by the
> builtins, it invokes UB 4 times, each time overwriting one byte
> after some variable (sc, then ss, then si and then sll).
Yup.
> If we are lucky, like at -O0 -mcpu=power10, there is just padding
> there or something that doesn't make the tests fail, if unlucky
> like with -O0 -mcpu=power10 -fstack-protector-strong,
> &sc + 1 == &expected_sc
> and so it overwrites the expected_sc variable.
Testcases do not always catch issues they were not designed for :-)
> The following patch fixes that by using arrays of 2 elements, so that
> the overwriting of 1 byte happens to the part of the same variable.
>
> Tested on powerpc64le-linux both without and with -fstack-protector-strong,
> ok for trunk and 15.2/14.4?
Okay everywhere (with a better commit message). Thanks!
Segher
> 2025-07-01 Jakub Jelinek <ja...@redhat.com>
>
> PR testsuite/120919
> * gcc.target/powerpc/builtin_altivec_tr_stxvr_runnable.c (main): Change
> sc, ss, si and sll vars from scalars to arrays of 2 elements,
> initialize and test just the first one though.
>
> --- gcc/testsuite/gcc.target/powerpc/builtin_altivec_tr_stxvr_runnable.c.jj
> 2023-06-03 15:32:05.230399713 +0200
> +++ gcc/testsuite/gcc.target/powerpc/builtin_altivec_tr_stxvr_runnable.c
> 2025-07-01 17:03:03.026845771 +0200
> @@ -27,10 +27,10 @@ int
> main () {
> int i;
> signed long sl;
> - signed char sc, expected_sc;
> - signed short ss, expected_ss;
> - signed int si, expected_si;
> - signed long long int sll, expected_sll;
> + signed char sc[2], expected_sc;
> + signed short ss[2], expected_ss;
> + signed int si[2], expected_si;
> + signed long long int sll[2], expected_sll;
> signed char *psc;
> signed short *pss;
> signed int *psi;
> @@ -41,56 +41,56 @@ main () {
> printf("Data to store [%d] = 0x%llx %llx\n", i, val.ull[1], val.ull[0]);
> #endif
>
> - psc = ≻
> - pss = &ss;
> - psi = &si;
> - psll = &sll;
> + psc = &sc[0];
> + pss = &ss[0];
> + psi = &si[0];
> + psll = &sll[0];
>
> sl = 1;
> - sc = 0xA1;
> + sc[0] = 0xA1;
> expected_sc = 0xA1;
> __builtin_altivec_tr_stxvrbx (store_data, sl, psc);
>
> - if (expected_sc != sc & 0xFF)
> + if (expected_sc != sc[0] & 0xFF)
> #if DEBUG
> printf(" ERROR: Signed char = 0x%x doesn't match expected value 0x%x\n",
> - sc & 0xFF, expected_sc);
> + sc[0] & 0xFF, expected_sc);
> #else
> abort();
> #endif
>
> - ss = 0x52;
> + ss[0] = 0x52;
> expected_ss = 0x1752;
> __builtin_altivec_tr_stxvrhx (store_data, sl, pss);
>
> - if (expected_ss != ss & 0xFFFF)
> + if (expected_ss != ss[0] & 0xFFFF)
> #if DEBUG
> printf(" ERROR: Signed short = 0x%x doesn't match expected value 0x%x\n",
> - ss, expected_ss) & 0xFFFF;
> + ss[0], expected_ss) & 0xFFFF;
> #else
> abort();
> #endif
>
> - si = 0x21;
> + si[0] = 0x21;
> expected_si = 0x54321721;
> __builtin_altivec_tr_stxvrwx (store_data, sl, psi);
>
> - if (expected_si != si)
> + if (expected_si != si[0])
> #if DEBUG
> printf(" ERROR: Signed int = 0x%x doesn't match expected value 0x%x\n",
> - si, expected_si);
> + si[0], expected_si);
> #else
> abort();
> #endif
>
> - sll = 0x12FFULL;
> + sll[0] = 0x12FFULL;
> expected_sll = 0xdcba9876543217FF;
> __builtin_altivec_tr_stxvrdx (store_data, sl, psll);
>
> - if (expected_sll != sll)
> + if (expected_sll != sll[0])
> #if DEBUG
> printf(" ERROR: Signed long long int = 0x%llx doesn't match expected
> value 0x%llx\n",
> - sll, expected_sll);
> + sll[0], expected_sll);
> #else
> abort();
> #endif
>
> Jakub
