https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95126
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:ed6fd2aed58f2cca99f15331bf68999c0e6df370 commit r13-990-ged6fd2aed58f2cca99f15331bf68999c0e6df370 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Sat Jun 4 12:21:51 2022 +0100 PR middle-end/95126: Expand small const structs as immediate constants. This patch resolves PR middle-end/95126 which is a code quality regression, by teaching the RTL expander to emit small const structs/unions as integer immediate constants. The motivating example from the bugzilla PR is: struct small{ short a,b; signed char c; }; extern int func(struct small X); void call_func(void) { static struct small const s = { 1, 2, 0 }; func(s); } which on x86_64 is currently compiled to: call_func: movzwl s.0+2(%rip), %eax movzwl s.0(%rip), %edx movzwl s.0+4(%rip), %edi salq $16, %rax orq %rdx, %rax salq $32, %rdi orq %rax, %rdi jmp func but with this patch is now optimized to: call_func: movl $131073, %edi jmp func 2022-06-04 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog PR middle-end/95126 * calls.cc (load_register_parameters): When loading a suitable immediate_const_ctor_p VAR_DECL into a single word_mode register, construct it directly in a pseudo rather than read it (by parts) from memory. * expr.cc (int_expr_size): Make tree argument a const_tree. (immediate_const_ctor_p): Helper predicate. Return true for simple constructors that may be materialized in a register. (expand_expr_real_1) [VAR_DECL]: When expanding a constant VAR_DECL with a suitable immediate_const_ctor_p constructor use store_constructor to materialize it directly in a pseudo. * expr.h (immediate_const_ctor_p): Prototype here. * varasm.cc (initializer_constant_valid_for_bitfield_p): Change VALUE argument from tree to const_tree. * varasm.h (initializer_constant_valid_for_bitfield_p): Update prototype. gcc/testsuite/ChangeLog PR middle-end/95126 * gcc.target/i386/pr95126-m32-1.c: New test case. * gcc.target/i386/pr95126-m32-2.c: New test case. * gcc.target/i386/pr95126-m32-3.c: New test case. * gcc.target/i386/pr95126-m32-4.c: New test case. * gcc.target/i386/pr95126-m64-1.c: New test case. * gcc.target/i386/pr95126-m64-2.c: New test case. * gcc.target/i386/pr95126-m64-3.c: New test case. * gcc.target/i386/pr95126-m64-4.c: New test case.
