On Fri, Nov 30, 2012 at 3:51 PM, Steven Bosscher <stevenb....@gmail.com> wrote:
>>>>> This one-liner causes following runtime test failure [1] for >>>>> alphaev68-linux-gnu: >>>>> >>>>> FAIL: gfortran.fortran-torture/execute/save_1.f90 execution, -O2 >>>>> FAIL: gfortran.fortran-torture/execute/save_1.f90 execution, -O2 >>>>> -fomit-frame-pointer -finline-functions >>>>> FAIL: gfortran.fortran-torture/execute/save_1.f90 execution, -O2 >>>>> -fomit-frame-pointer -finline-functions -funroll-loops >>>>> FAIL: gfortran.fortran-torture/execute/save_1.f90 execution, -O2 >>>>> -fbounds-check >>>>> >>>>> The patch miscompiles libgfortran library. >>>>> >>>>> I will provide more info tomorrow, any hint what/where should I look >>>>> for differences? >>>> >>>> Anywhere. The bug disabled a large part of alias analysis. >>>> >>>> Perhaps you can bisect it and backport the fix along the steps. >>> >>> Or open a PR and assign it to me, ultimately I'm responsible for this >>> breakage. >> >> I have found the problem. Luckily, it is the testcase that is >> miscompiled. The problem is in sched1 pass that moves write to an >> address "addrX" that happens to be aliased with AND mutilated address >> "addrY & -7". The improved alias analysis does not notice that the >> write is inside (addr & -7) region, allowing write to be moved after >> read. > > Based on this description of the problem, I remembered these patches > from Alexandre: > > 2012-07-06 Alexandre Oilva <> > > PR rtl-optimization/53827 > PR debug/53671 > PR debug/49888 > * alias.c (memrefs_conflict_p): Adjust offset and size by the > same amount for alignment ANDs. > > 2012-06-21 Alexandre Oliva <> > > PR debug/53671 > PR debug/49888 > * alias.c (memrefs_conflict_p): Improve handling of AND for alignment. > > > They are r188868 and r189325. Can you try revert these and see if that > fixes your problem (probably at the expense of some other problem > returning, but at least it'd be a good place to start looking > further...). Yes backing out these revisions with attached patch fixes the runtime failure! Uros.
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