On 18 October 2016 at 05:18, Markus Trippelsdorf <mar...@trippelsdorf.de> wrote: > On 2016.10.18 at 05:13 +0200, Markus Trippelsdorf wrote: >> On 2016.10.17 at 17:23 -0500, Bill Schmidt wrote: >> > Hi, >> > >> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77916 identifies a situation >> > where SLSR will ICE when exposed to a cast from integer to pointer. This >> > is because we try to convert a PLUS_EXPR with an addend of -1 * S into a >> > MINUS_EXPR with a subtrahend of S, but the base operand is unexpectedly >> > of pointer type. This patch recognizes when pointer arithmetic is taking >> > place and ensures that we use a POINTER_PLUS_EXPR at all such times. In >> > the case of the PR, this occurs in the logic where the stride S is a known >> > constant value, but the same problem could occur when it is an SSA_NAME >> > without known value. Both possibilities are handled here. >> > >> > Fixing the code to ensure that the unknown stride case always uses an >> > initializer for a negative increment allows us to remove the stopgap fix >> > added for PR77937 as well. >> > >> > Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no >> > regressions, committed. >> >> Perhaps you should consider building ffmpeg with -O3 -march=amdfam10 on >> X86_64 before committing these patches, because you broke it for the >> third time in the last couple of days. >> >> markus@x4 ffmpeg % cat h264dsp.i >> extern int fn2(int); >> extern int fn3(int); >> int a, b, c; >> void fn1(long p1) { >> char *d; >> for (;; d += p1) { >> d[0] = fn2(1 >> c >> 1); >> fn2(c >> a); >> d[1] = fn3(d[1]) >> 1; >> d[6] = fn3(d[6] * b + 1) >> 1; >> d[7] = fn3(d[7] * b + 1) >> 1; >> d[8] = fn3(d[8] * b + 1) >> 1; >> } >> } >> >> markus@x4 ffmpeg % gcc -O3 -march=amdfam10 -c h264dsp.i >> h264dsp.i: In function ‘fn1’: >> h264dsp.i:4:6: internal compiler error: in replace_one_candidate, at >> gimple-ssa-strength-reduction.c:3375 >> void fn1(long p1) { >> ^~~ >> 0x12773a9 replace_one_candidate >> ../../gcc/gcc/gimple-ssa-strength-reduction.c:3375 >> 0x127af77 replace_profitable_candidates >> ../../gcc/gcc/gimple-ssa-strength-reduction.c:3486 >> 0x127aeeb replace_profitable_candidates >> ../../gcc/gcc/gimple-ssa-strength-reduction.c:3495 >> 0x127f3ee analyze_candidates_and_replace >> ../../gcc/gcc/gimple-ssa-strength-reduction.c:3574 >> 0x127f3ee execute >> ../../gcc/gcc/gimple-ssa-strength-reduction.c:3648 > > Just figured out that this testcase is identical to: > gcc/testsuite/gcc.dg/torture/pr77937-2.c > > So please run the testsuite on X86_64 in the future. >
I'm not sure whether Markus means that pr77937-2 fails since this commit? I'm seeing ICEs on pr77937-2 on some arm targets: http://people.linaro.org/~christophe.lyon/cross-validation/gcc/trunk/241285/report-build-info.html but I'm not 100% sure it was caused by this patch (the regression happened between r241273 and r241285), I haven't looked in details yet. Christophe > -- > Markus
