diff options
Diffstat (limited to 'gcc/config/arm/arm.c')
| -rw-r--r-- | gcc/config/arm/arm.c | 86 |
1 files changed, 68 insertions, 18 deletions
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c index 8cc1be2..86c897e 100644 --- a/gcc/config/arm/arm.c +++ b/gcc/config/arm/arm.c @@ -19216,7 +19216,36 @@ arm_compute_save_reg_mask (void) return save_reg_mask; } -/* Compute a bit mask of which registers need to be +/* Return a mask for the call-clobbered low registers that are unused + at the end of the prologue. */ +static unsigned long +thumb1_prologue_unused_call_clobbered_lo_regs (void) +{ + unsigned long mask = 0; + + for (int reg = 0; reg <= LAST_LO_REGNUM; reg++) + if (!callee_saved_reg_p (reg) + && !REGNO_REG_SET_P (df_get_live_out (ENTRY_BLOCK_PTR_FOR_FN (cfun)), + reg)) + mask |= 1 << reg; + return mask; +} + +/* Similarly for the start of the epilogue. */ +static unsigned long +thumb1_epilogue_unused_call_clobbered_lo_regs (void) +{ + unsigned long mask = 0; + + for (int reg = 0; reg <= LAST_LO_REGNUM; reg++) + if (!callee_saved_reg_p (reg) + && !REGNO_REG_SET_P (df_get_live_in (EXIT_BLOCK_PTR_FOR_FN (cfun)), + reg)) + mask |= 1 << reg; + return mask; +} + +/* Compute a bit mask of which core registers need to be saved on the stack for the current function. */ static unsigned long thumb1_compute_save_reg_mask (void) @@ -19247,10 +19276,19 @@ thumb1_compute_save_reg_mask (void) if (mask & 0xff || thumb_force_lr_save ()) mask |= (1 << LR_REGNUM); - /* Make sure we have a low work register if we need one. - We will need one if we are going to push a high register, - but we are not currently intending to push a low register. */ + bool call_clobbered_scratch + = (thumb1_prologue_unused_call_clobbered_lo_regs () + && thumb1_epilogue_unused_call_clobbered_lo_regs ()); + + /* Make sure we have a low work register if we need one. We will + need one if we are going to push a high register, but we are not + currently intending to push a low register. However if both the + prologue and epilogue have a spare call-clobbered low register, + then we won't need to find an additional work register. It does + not need to be the same register in the prologue and + epilogue. */ if ((mask & 0xff) == 0 + && !call_clobbered_scratch && ((mask & 0x0f00) || TARGET_BACKTRACE)) { /* Use thumb_find_work_register to choose which register @@ -24439,12 +24477,7 @@ thumb1_unexpanded_epilogue (void) unsigned long mask = live_regs_mask & 0xff; int next_hi_reg; - /* The available low registers depend on the size of the value we are - returning. */ - if (size <= 12) - mask |= 1 << 3; - if (size <= 8) - mask |= 1 << 2; + mask |= thumb1_epilogue_unused_call_clobbered_lo_regs (); if (mask == 0) /* Oh dear! We have no low registers into which we can pop @@ -24452,7 +24485,7 @@ thumb1_unexpanded_epilogue (void) internal_error ("no low registers available for popping high registers"); - for (next_hi_reg = 8; next_hi_reg < 13; next_hi_reg++) + for (next_hi_reg = 12; next_hi_reg > LAST_LO_REGNUM; next_hi_reg--) if (live_regs_mask & (1 << next_hi_reg)) break; @@ -24460,7 +24493,7 @@ thumb1_unexpanded_epilogue (void) { /* Find lo register(s) into which the high register(s) can be popped. */ - for (regno = 0; regno <= LAST_LO_REGNUM; regno++) + for (regno = LAST_LO_REGNUM; regno >= 0; regno--) { if (mask & (1 << regno)) high_regs_pushed--; @@ -24468,20 +24501,22 @@ thumb1_unexpanded_epilogue (void) break; } - mask &= (2 << regno) - 1; /* A noop if regno == 8 */ + if (high_regs_pushed == 0 && regno >= 0) + mask &= ~((1 << regno) - 1); /* Pop the values into the low register(s). */ thumb_pop (asm_out_file, mask); /* Move the value(s) into the high registers. */ - for (regno = 0; regno <= LAST_LO_REGNUM; regno++) + for (regno = LAST_LO_REGNUM; regno >= 0; regno--) { if (mask & (1 << regno)) { asm_fprintf (asm_out_file, "\tmov\t%r, %r\n", next_hi_reg, regno); - for (next_hi_reg++; next_hi_reg < 13; next_hi_reg++) + for (next_hi_reg--; next_hi_reg > LAST_LO_REGNUM; + next_hi_reg--) if (live_regs_mask & (1 << next_hi_reg)) break; } @@ -24863,10 +24898,20 @@ thumb1_expand_prologue (void) break; /* Here we need to mask out registers used for passing arguments - even if they can be pushed. This is to avoid using them to stash the high - registers. Such kind of stash may clobber the use of arguments. */ + even if they can be pushed. This is to avoid using them to + stash the high registers. Such kind of stash may clobber the + use of arguments. */ pushable_regs = l_mask & (~arg_regs_mask); - if (lr_needs_saving) + pushable_regs |= thumb1_prologue_unused_call_clobbered_lo_regs (); + + /* Normally, LR can be used as a scratch register once it has been + saved; but if the function examines its own return address then + the value is still live and we need to avoid using it. */ + bool return_addr_live + = REGNO_REG_SET_P (df_get_live_out (ENTRY_BLOCK_PTR_FOR_FN (cfun)), + LR_REGNUM); + + if (lr_needs_saving || return_addr_live) pushable_regs &= ~(1 << LR_REGNUM); if (pushable_regs == 0) @@ -24907,6 +24952,11 @@ thumb1_expand_prologue (void) push_mask |= 1 << LR_REGNUM; real_regs_mask |= 1 << LR_REGNUM; lr_needs_saving = false; + /* If the return address is not live at this point, we + can add LR to the list of registers that we can use + for pushes. */ + if (!return_addr_live) + pushable_regs |= 1 << LR_REGNUM; } insn = thumb1_emit_multi_reg_push (push_mask, real_regs_mask); |