https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100841
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:50b1de860a58bf85b40a72219bc2fdfaf0dff355 commit r12-1167-g50b1de860a58bf85b40a72219bc2fdfaf0dff355 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Jun 2 22:09:53 2021 +0200 xtensa: Fix 2 warnings during xtensa build [PR100841] When building gcc targetting xtensa-linux, there are 2 warnings the PR complains about: ../../gcc/dwarf2cfi.c: In function âvoid init_one_dwarf_reg_size(int, machine_mode, rtx, machine_mode, init_one_dwarf_reg_state*)â: ../../gcc/dwarf2cfi.c:291:12: warning: comparison of integer expressions of different signedness: âconst unsigned intâ and âintâ [-Wsign-compare] 291 | if (rnum >= DWARF_FRAME_REGISTERS) ../../gcc/function.c: In function âvoid gen_call_used_regs_seq(rtx_insn*, unsigned int)â: ../../gcc/function.c:5897:63: warning: comparison of unsigned expression in â< 0â is always false [-Wtype-limits] 5897 | if (crtl->uses_only_leaf_regs && LEAF_REG_REMAP (regno) < 0) which might during bootstrap or when configured with --enable-werror-always be turned into errors. The first one is the -Wsign-compare warning, in c-family we do: 2281 /* Do not warn if the signed quantity is an unsuffixed integer 2282 literal (or some static constant expression involving such 2283 literals or a conditional expression involving such literals) 2284 and it is non-negative. */ 2285 if (tree_expr_nonnegative_warnv_p (sop, &ovf)) 2286 /* OK */; and so don't warn if that function determines the expression is non-negative. But xtensa defines DWARF_FRAME_REGISTERS as (16 + (something ? 0 : 1)) and that isn't handled by tree_expr_nonnegative_warnv_p, VRP can handle it of course, but that is much later. The second chunk rewrites it into a form that tree_expr_nonnegative_warnv_p can handle, in particular (something ? 16 : 16 + 1), where for COND_EXPRs that function checks both the 2nd and 3rd operand of the ternary operator and if both are nonnegative, returns true. The other warning has been introduced fairly recently; LEAF_REG_REMAP is currently used by 2 targets only, and is documented to yield -1 if a hard reg number can't be remapped and the remapped register number otherwise. That means that the type of the expression should be signed (otherwise -1 could never appear), and on SPARC indeed it is defined as extern char leaf_reg_remap[]; #define LEAF_REG_REMAP(REGNO) (leaf_reg_remap[REGNO]) so unless the host is -funsigned-char by default it works fine. I guess sparc.[ch] should be fixed to use signed char of leaf_reg_remap, Eric? The argument to LEAF_REG_REMAP is often unsigned int though, hard register numbers are usually not negative, and thus the warning. I think xtensa doesn't have 2G hard registers and so it is ok to just cast it to int. 2021-06-02 Jakub Jelinek <ja...@redhat.com> PR target/100841 * config/xtensa/xtensa.h (LEAF_REG_REMAP): Cast REGNO to int to avoid -Wtype-limits warnings. (DWARF_FRAME_REGISTER): Rewrite into ternary operator with addition in operands to avoid -Wsign-compare warnings.
