When compiling Python 3.5.4 or 3.6.3 with -mfpmath=sse on x86 Linux using gcc 7.2.0, I get an ICE/segfault in lra_eliminate_reg_if_possible while compiling cmathmodule.c:

building 'cmath' extension
gcc -pthread -fPIC -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -O2 -march=native 
-pipe -fomit-frame-pointer -mfpmath=sse -O2 -march=native -pipe -fomit-frame-pointer -mfpmath=sse 
-Werror=declaration-after-statement -I./Include -I. -I/home/aidan/src/Python-3.5.4/Include 
-I/home/aidan/src/Python-3.5.4 -c /home/aidan/src/Python-3.5.4/Modules/cmathmodule.c -o 
build/temp.linux-i686-3.5/home/aidan/src/Python-3.5.4/Modules/cmathmodule.o
In file included from /home/aidan/src/Python-3.5.4/Modules/cmathmodule.c:11:0:
/home/aidan/src/Python-3.5.4/Modules/clinic/cmathmodule.c.h: In function ‘cmath_acos’:
/home/aidan/src/Python-3.5.4/Modules/clinic/cmathmodule.c.h:44:1: internal compiler error: Segmentation fault
 }
 ^
Please submit a full bug report,
with preprocessed source if appropriate.

C-Reduce produced the following reduced test case which triggers the same ICE/segfault:

typedef struct {
  double a
} b;
b c;
d, e;
f() {
  _setjmp();
  b g;
  if (d)
    g.a = copysign(e, d);
  c = g;
}

A suitable set of compile options to reproduce this using the above test case is:

gcc -fPIC -O1 -march=prescott -mfpmath=sse -c cmathmodule-reduced.i

The ICE does not appear to occur with gcc 6.4.0, nor does it occur if either of -mfpmath=sse or -fPIC are disabled. It is, however, still present in the gcc 7 branch as of at least r255440. Backtrace is as follows:

Program received signal SIGSEGV, Segmentation fault.
0x084cb7f4 in lra_eliminate_reg_if_possible (loc=0xb772ad38) at ../.././gcc/lra-eliminations.c:1385
1385          || ! TEST_HARD_REG_BIT (lra_no_alloc_regs, regno))
(gdb) bt
#0  0x084cb7f4 in lra_eliminate_reg_if_possible (loc=0xb772ad38) at ../.././gcc/lra-eliminations.c:1385
#1  0x084bc1f0 in (anonymous namespace)::address_eliminator::address_eliminator (this=0xbfffdb90, ad=<optimized out>)
    at ../.././gcc/lra-constraints.c:362
#2  0x084bc320 in satisfies_memory_constraint_p (op=op@entry=0xb772ad40, constraint=CONSTRAINT_m)
    at ../.././gcc/lra-constraints.c:401
#3  0x084c2b3a in process_alt_operands (only_alternative=<optimized out>) at ../.././gcc/lra-constraints.c:2252
#4  curr_insn_transform (check_only_p=check_only_p@entry=false) at ../.././gcc/lra-constraints.c:3848
#5  0x084c5880 in lra_constraints (first_p=false) at ../.././gcc/lra-constraints.c:4863
#6  0x084b620e in lra (f=0x0) at ../.././gcc/lra.c:2392
#7  0x08477648 in do_reload () at ../.././gcc/ira.c:5478
#8  (anonymous namespace)::pass_reload::execute (this=0x96ec4d0) at ../.././gcc/ira.c:5662
#9  0x0853a145 in execute_one_pass (pass=0x96ec4d0) at ../.././gcc/passes.c:2465
#10 0x0853a94f in execute_pass_list_1 (pass=0x96ec4d0) at ../.././gcc/passes.c:2554
#11 0x0853a962 in execute_pass_list_1 (pass=0x96eb950, pass@entry=0x96e9280) at ../.././gcc/passes.c:2555
#12 0x0853a9a9 in execute_pass_list (fn=0xb7720000, pass=0x96e9280) at ../.././gcc/passes.c:2565
#13 0x082c18cc in cgraph_node::expand (this=0xb7726000) at ../.././gcc/cgraphunit.c:2042
#14 0x082c2c08 in expand_all_functions () at ../.././gcc/cgraphunit.c:2178
#15 symbol_table::compile (this=this@entry=0xb76680c4) at ../.././gcc/cgraphunit.c:2535
#16 0x082c48e9 in symbol_table::compile (this=0xb76680c4) at ../.././gcc/cgraphunit.c:2595
#17 symbol_table::finalize_compilation_unit (this=0xb76680c4) at ../.././gcc/cgraphunit.c:2625
#18 0x085f417a in compile_file () at ../.././gcc/toplev.c:492
#19 0x081a14e3 in do_compile () at ../.././gcc/toplev.c:2003
#20 toplev::main (this=0xbfffe8fe, argc=<optimized out>, argv=<optimized out>) at ../.././gcc/toplev.c:2138
#21 0x081a3741 in main (argc=10, argv=0xbfffe9c4) at ../.././gcc/main.c:39