| Message ID | 1447088342.3867.27.camel@ubuntu-sellcey |
|---|---|
| State | New |
| Headers | show |
On 11/09/2015 05:59 PM, Steve Ellcey wrote: > Here is a version with the code moved into a new function. How does > this look? > > 2015-11-09 Steve Ellcey <sellcey@imgtec.com> > > * optabs.c (prepare_libcall_arg): New function. > (expand_fixed_convert): Add call to prepare_libcall_arg. Hold on a moment - I see that emit_library_call_value_1 calls promote_function_mode for arguments. Can you investigate why that doesn't do what you need? Bernd
On Mon, 2015-11-09 at 21:47 +0100, Bernd Schmidt wrote: > On 11/09/2015 05:59 PM, Steve Ellcey wrote: > > Here is a version with the code moved into a new function. How does > > this look? > > > > 2015-11-09 Steve Ellcey <sellcey@imgtec.com> > > > > * optabs.c (prepare_libcall_arg): New function. > > (expand_fixed_convert): Add call to prepare_libcall_arg. > > Hold on a moment - I see that emit_library_call_value_1 calls > promote_function_mode for arguments. Can you investigate why that > doesn't do what you need? > > > Bernd emit_library_call_value_1 has no way of knowing if the promotion should be signed or unsigned because it has a mode (probably QImode or HImode) that it knows may need to be promoted to SImode but it has no way to know if that should be a signed or unsigned promotion because it has no tree type information about the library call argument types. Right now it guesses based on the return type but it may guess wrong when converting an unsigned int to a signed fixed type or visa versa. By doing the promotion in expand_fixed_convert GCC can use the uintp argument to ensure that the signedness of the promotion is done correctly. We could pass that argument into emit_library_call_value_1 so it can do the correct promotion but that would require changing the argument list for emit_library_call and emit_library_call_value_1 and changing all the other call locations for those functions and that seemed like overkill. Steve Ellcey
On 11/09/2015 10:10 PM, Steve Ellcey wrote: > emit_library_call_value_1 has no way of knowing if the promotion should > be signed or unsigned because it has a mode (probably QImode or HImode) > that it knows may need to be promoted to SImode but it has no way to > know if that should be a signed or unsigned promotion because it has no > tree type information about the library call argument types. > > Right now it guesses based on the return type but it may guess wrong > when converting an unsigned int to a signed fixed type or visa versa. That's not quite how I read the code, but it doesn't matter - the lack of a type seems to be a real issue. Since I don't see anything better, please install your patch. Bernd
diff --git a/gcc/optabs.c b/gcc/optabs.c index fdcdc6a..fb25f90 100644 --- a/gcc/optabs.c +++ b/gcc/optabs.c @@ -4838,6 +4838,33 @@ expand_fix (rtx to, rtx from, int unsignedp) } } + +/* Promote integer arguments for a libcall if necessary. + emit_library_call_value cannot do the promotion because it does not + know if it should do a signed or unsigned promotion. This is because + there are no tree types defined for libcalls. */ + +static rtx +prepare_libcall_arg (rtx arg, int uintp) +{ + machine_mode mode = GET_MODE (arg); + machine_mode arg_mode; + if (SCALAR_INT_MODE_P (mode)) + { + /* If we need to promote the integer function argument we need to do + it here instead of inside emit_library_call_value because in + emit_library_call_value we don't know if we should do a signed or + unsigned promotion. */ + + int unsigned_p = 0; + arg_mode = promote_function_mode (NULL_TREE, mode, + &unsigned_p, NULL_TREE, 0); + if (arg_mode != mode) + return convert_to_mode (arg_mode, arg, uintp); + } + return arg; +} + /* Generate code to convert FROM or TO a fixed-point. If UINTP is true, either TO or FROM is an unsigned integer. If SATP is true, we need to saturate the result. */ @@ -4880,6 +4907,9 @@ expand_fixed_convert (rtx to, rtx from, int uintp, int satp) libfunc = convert_optab_libfunc (tab, to_mode, from_mode); gcc_assert (libfunc); + from = prepare_libcall_arg (from, uintp); + from_mode = GET_MODE (from); + start_sequence (); value = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST, to_mode, 1, from, from_mode);