There is no need to store callee-saved registers in prologue if the function would never return. Size optimization is paramount for the microcontroller-class PRU.
Some backends save some registers for noreturn functions. But for PRU debuggability is a less concern because GDB has not been ported yet for PRU. gcc/ChangeLog: * config/pru/pru.cc (prologue_saved_reg_p): Skip saving if function will not return. gcc/testsuite/ChangeLog: * gcc.target/pru/noreturn-prologue-1.c: New test. * gcc.target/pru/noreturn-prologue-2.c: New test. Signed-off-by: Dimitar Dimitrov <dimi...@dinux.eu> --- gcc/config/pru/pru.cc | 4 ++++ gcc/testsuite/gcc.target/pru/noreturn-prologue-1.c | 10 ++++++++++ gcc/testsuite/gcc.target/pru/noreturn-prologue-2.c | 11 +++++++++++ 3 files changed, 25 insertions(+) create mode 100644 gcc/testsuite/gcc.target/pru/noreturn-prologue-1.c create mode 100644 gcc/testsuite/gcc.target/pru/noreturn-prologue-2.c diff --git a/gcc/config/pru/pru.cc b/gcc/config/pru/pru.cc index a76451f4223..e5ec398d2db 100644 --- a/gcc/config/pru/pru.cc +++ b/gcc/config/pru/pru.cc @@ -443,6 +443,10 @@ prologue_saved_reg_p (int regno) { gcc_assert (GP_REG_P (regno)); + /* Do not save the register if function will not return. */ + if (TREE_THIS_VOLATILE (current_function_decl)) + return false; + if (df_regs_ever_live_p (regno) && !call_used_or_fixed_reg_p (regno)) return true; diff --git a/gcc/testsuite/gcc.target/pru/noreturn-prologue-1.c b/gcc/testsuite/gcc.target/pru/noreturn-prologue-1.c new file mode 100644 index 00000000000..af69e52d925 --- /dev/null +++ b/gcc/testsuite/gcc.target/pru/noreturn-prologue-1.c @@ -0,0 +1,10 @@ +/* Ensure prologues are not generated for noreturn functions. */ +/* { dg-do assemble } */ +/* { dg-options "-Os" } */ +/* { dg-final { object-size text == 0 } } */ + +void test(void) +{ + asm volatile ("# \n\t" : : : "r5", "r10"); + __builtin_unreachable (); +} diff --git a/gcc/testsuite/gcc.target/pru/noreturn-prologue-2.c b/gcc/testsuite/gcc.target/pru/noreturn-prologue-2.c new file mode 100644 index 00000000000..8d12a9c462b --- /dev/null +++ b/gcc/testsuite/gcc.target/pru/noreturn-prologue-2.c @@ -0,0 +1,11 @@ +/* Ensure prologues are not generated for noreturn functions. */ +/* { dg-do assemble } */ +/* { dg-options "-Os" } */ +/* { dg-final { object-size text == 4 } } */ + +void test(void) +{ + asm volatile ("# \n\t" : : : "r0", "r9"); + for (;;) + ; +} -- 2.45.0