On Mon, Jan 25, 2016 at 4:40 AM, Richard Biener <richard.guent...@gmail.com> wrote: > On Fri, Jan 22, 2016 at 7:55 PM, H.J. Lu <hongjiu...@intel.com> wrote: >> Without the fix for PR 65656, g++ miscompiles __builtin_constant_p in >> wi::lrshift in wide-int.h. Add a check with PR 65656 testcase to verify >> that C++ __builtin_constant_p works properly. >> >> Tested on x86-64 with working GCC: >> >> gcc/auto-host.h:/* #undef HAVE_WORKING_CXX_BUILTIN_CONSTANT_P */ >> prev-gcc/auto-host.h:/* #undef HAVE_WORKING_CXX_BUILTIN_CONSTANT_P */ >> stage1-gcc/auto-host.h:#define HAVE_WORKING_CXX_BUILTIN_CONSTANT_P 1 >> >> and broken GCC: >> >> gcc/auto-host.h:/* #undef HAVE_WORKING_CXX_BUILTIN_CONSTANT_P */ >> prev-gcc/auto-host.h:/* #undef HAVE_WORKING_CXX_BUILTIN_CONSTANT_P */ >> stage1-gcc/auto-host.h:/* #undef HAVE_WORKING_CXX_BUILTIN_CONSTANT_P */ >> >> Ok for trunk? > > I have a hard time seeing how we are "miscompiling" > > if (STATIC_CONSTANT_P (xi.precision > HOST_BITS_PER_WIDE_INT) > ? xi.len == 1 && xi.val[0] >= 0 > : xi.precision <= HOST_BITS_PER_WIDE_INT) > > anything that relies on __builtin_constant_p () for sematics is fishy so why > is this not simply an lrshfit implementation bug? >
We hit this via: Breakpoint 1, wi::lrshift<generic_wide_int<fixed_wide_int_storage<192> >, generic_wide_int<fixed_wide_int_storage<192> > > (x=..., y=...) at /export/gnu/import/git/sources/gcc-release/gcc/wide-int.h:2898 2898 val[0] = xi.to_uhwi () >> shift; (gdb) bt #0 wi::lrshift<generic_wide_int<fixed_wide_int_storage<192> >, generic_wide_int<fixed_wide_int_storage<192> > > (x=..., y=...) at /export/gnu/import/git/sources/gcc-release/gcc/wide-int.h:2898 #1 0x00000000009e7bbe in wi::rshift<generic_wide_int<fixed_wide_int_storage<192> >, generic_wide_int<fixed_wide_int_storage<192> > > (sgn=<optimized out>, y=..., x=...) at /export/gnu/import/git/sources/gcc-release/gcc/wide-int.h:2947 #2 bit_value_binop_1 (code=code@entry=RSHIFT_EXPR, type=type@entry=0x7fffefe82dc8, val=val@entry=0x7fffffffd7c0, mask=mask@entry=0x7fffffffd790, r1type=0x7fffefe82dc8, r1val=..., r1mask=..., r2type=0x7fffefd6b690, r2val=..., r2mask=...) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:1348 #3 0x00000000009e9e7b in bit_value_binop (code=code@entry=RSHIFT_EXPR, type=0x7fffefe82dc8, rhs1=rhs1@entry=0x7fffefd71708, rhs2=<optimized out>) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:1549 #4 0x00000000009eb520 in evaluate_stmt (stmt=stmt@entry=0x7fffefe9a160) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:1785 #5 0x00000000009ec8d2 in visit_assignment (stmt=stmt@entry=0x7fffefe9a160, output_p=output_p@entry=0x7fffffffdba0) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:2258 #6 0x00000000009ec9c2 in ccp_visit_stmt (stmt=0x7fffefe9a160, taken_edge_p=0x7fffffffdba8, output_p=0x7fffffffdba0) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:2336 ---Type <return> to continue, or q <return> to quit--- #7 0x0000000000a4efcf in simulate_stmt (stmt=stmt@entry=0x7fffefe9a160) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-propagate.c:348 #8 0x0000000000a50f79 in simulate_block (block=<optimized out>) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-propagate.c:471 #9 ssa_propagate ( visit_stmt=visit_stmt@entry=0x9ec937 <ccp_visit_stmt(gimple, edge*, tree*)>, visit_phi=visit_phi@entry=0x9e6aa5 <ccp_visit_phi_node(gphi*)>) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-propagate.c:888 #10 0x00000000009e6295 in do_ssa_ccp () at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:2382 #11 (anonymous namespace)::pass_ccp::execute (this=<optimized out>) at /export/gnu/import/git/sources/gcc-release/gcc/tree-ssa-ccp.c:2415 #12 0x000000000089ca0c in execute_one_pass (pass=pass@entry=0x19b4bf0) at /export/gnu/import/git/sources/gcc-release/gcc/passes.c:2330 #13 0x000000000089cd62 in execute_pass_list_1 (pass=0x19b4bf0) at /export/gnu/import/git/sources/gcc-release/gcc/passes.c:2382 #14 0x000000000089cd7f in execute_pass_list_1 (pass=0x19b4a70, pass@entry=0x19b48f0) at /export/gnu/import/git/sources/gcc-release/gcc/passes.c:2383 #15 0x000000000089cd9c in execute_pass_list (fn=0x7fffefe98000, pass=0x19b48f0) at /export/gnu/import/git/sources/gcc-release/gcc/passes.c:2393 #16 0x000000000089ba57 in do_per_function_toporder ( callback=callback@entry=0x89cd83 <execute_pass_list(function*, opt_pass*)>, ---Type <return> to continue, or q <return> to quit--- data=0x19b48f0) at /export/gnu/import/git/sources/gcc-release/gcc/passes.c:1728 #17 0x000000000089d3e3 in execute_ipa_pass_list (pass=0x19b4890) at /export/gnu/import/git/sources/gcc-release/gcc/passes.c:2736 #18 0x000000000066f3ac in ipa_passes () at /export/gnu/import/git/sources/gcc-release/gcc/cgraphunit.c:2172 #19 symbol_table::compile (this=this@entry=0x7fffefd6b000) at /export/gnu/import/git/sources/gcc-release/gcc/cgraphunit.c:2313 #20 0x0000000000670be5 in symbol_table::finalize_compilation_unit ( this=0x7fffefd6b000) at /export/gnu/import/git/sources/gcc-release/gcc/cgraphunit.c:2462 #21 0x000000000058ea41 in c_write_global_declarations () at /export/gnu/import/git/sources/gcc-release/gcc/c/c-decl.c:10822 #22 0x0000000000939509 in compile_file () at /export/gnu/import/git/sources/gcc-release/gcc/toplev.c:613 #23 0x000000000093b3c4 in do_compile () at /export/gnu/import/git/sources/gcc-release/gcc/toplev.c:2067 #24 toplev::main (this=this@entry=0x7fffffffdf60, argc=argc@entry=15, argv=argv@entry=0x7fffffffe068) at /export/gnu/import/git/sources/gcc-release/gcc/toplev.c:2165 #25 0x0000000000f50ab7 in main (argc=15, argv=0x7fffffffe068) at /export/gnu/import/git/sources/gcc-release/gcc/main.c:39 (gdb) p x $2 = (const generic_wide_int<fixed_wide_int_storage<192> > &) @0x7fffffffd670: {<fixed_wide_int_storage<192>> = {val = {4294967169, 0, 140737217214936, 92}, len = 1}, static is_sign_extended = <optimized out>} (gdb) p y $3 = (const generic_wide_int<fixed_wide_int_storage<192> > &) @0x7fffffffd640: {<fixed_wide_int_storage<192>> = {val = {64, 824633720833, -4294967168, 140737218308160}, len = 1}, static is_sign_extended = <optimized out>} (gdb) p xi $3 = {<wide_int_ref_storage<true>> = {<wi::storage_ref> = { val = 0x7fffffffcfe0, len = 2, precision = 192}, scratch = {64, 8589921072}}, static is_sign_extended = <optimized out>} (gdb) p yi $4 = {<wide_int_ref_storage<true>> = {<wi::storage_ref> = { val = 0x7fffffffcbc0, len = 1, precision = 192}, scratch = { 140737488344768, 140737488343008}}, static is_sign_extended = <optimized out>} (gdb) Somehow PR 65656 miscompiled: if (STATIC_CONSTANT_P (xi.precision > HOST_BITS_PER_WIDE_INT) ? xi.len == 1 && xi.val[0] >= 0 : xi.precision <= HOST_BITS_PER_WIDE_INT) which turned the expression into true and hit val[0] = xi.to_uhwi () >> shift; result.set_len (1); -- H.J.