From aa8fd7f65683ef9c3b6d2e9306bea2f28b5cadf7 Mon Sep 17 00:00:00 2001 From: Lulu Cheng Date: Thu, 7 Jul 2022 18:07:28 +0800 Subject: [PATCH] LoongArch: Modify fp_sp_offset and gp_sp_offset's calculation method when frame->mask or frame->fmask is zero. Under the LA architecture, when the stack is dropped too far, the process of dropping the stack is divided into two steps. step1: After dropping the stack, save callee saved registers on the stack. step2: The rest of it. The stack drop operation is optimized when frame->total_size minus frame->sp_fp_offset is an integer multiple of 4096, can reduce the number of instructions required to drop the stack. However, this optimization is not effective because of the original calculation method The following case: int main() { char buf[1024 * 12]; printf ("%p\n", buf); return 0; } As you can see from the generated assembler, the old GCC has two more instructions than the new GCC, lines 14 and line 24. new old 10 main: | 11 main: 11 addi.d $r3,$r3,-16 | 12 lu12i.w $r13,-12288>>12 12 lu12i.w $r13,-12288>>12 | 13 addi.d $r3,$r3,-2032 13 lu12i.w $r5,-12288>>12 | 14 ori $r13,$r13,2016 14 lu12i.w $r12,12288>>12 | 15 lu12i.w $r5,-12288>>12 15 st.d $r1,$r3,8 | 16 lu12i.w $r12,12288>>12 16 add.d $r12,$r12,$r5 | 17 st.d $r1,$r3,2024 17 add.d $r3,$r3,$r13 | 18 add.d $r12,$r12,$r5 18 add.d $r5,$r12,$r3 | 19 add.d $r3,$r3,$r13 19 la.local $r4,.LC0 | 20 add.d $r5,$r12,$r3 20 bl %plt(printf) | 21 la.local $r4,.LC0 21 lu12i.w $r13,12288>>12 | 22 bl %plt(printf) 22 add.d $r3,$r3,$r13 | 23 lu12i.w $r13,8192>>12 23 ld.d $r1,$r3,8 | 24 ori $r13,$r13,2080 24 or $r4,$r0,$r0 | 25 add.d $r3,$r3,$r13 25 addi.d $r3,$r3,16 | 26 ld.d $r1,$r3,2024 26 jr $r1 | 27 or $r4,$r0,$r0 | 28 addi.d $r3,$r3,2032 | 29 jr $r1 gcc/ChangeLog: * config/loongarch/loongarch.cc (loongarch_compute_frame_info): Modify fp_sp_offset and gp_sp_offset's calculation method, when frame->mask or frame->fmask is zero, don't minus UNITS_PER_WORD or UNITS_PER_FP_REG. gcc/testsuite/ChangeLog: * gcc.target/loongarch/prolog-opt.c: New test. --- gcc/config/loongarch/loongarch.cc | 12 +++++++++--- gcc/testsuite/gcc.target/loongarch/prolog-opt.c | 15 +++++++++++++++ 2 files changed, 24 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/gcc.target/loongarch/prolog-opt.c diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc index d72b256df51..5c9a33c14f7 100644 --- a/gcc/config/loongarch/loongarch.cc +++ b/gcc/config/loongarch/loongarch.cc @@ -917,8 +917,12 @@ loongarch_compute_frame_info (void) frame->frame_pointer_offset = offset; /* Next are the callee-saved FPRs. */ if (frame->fmask) - offset += LARCH_STACK_ALIGN (num_f_saved * UNITS_PER_FP_REG); - frame->fp_sp_offset = offset - UNITS_PER_FP_REG; + { + offset += LARCH_STACK_ALIGN (num_f_saved * UNITS_PER_FP_REG); + frame->fp_sp_offset = offset - UNITS_PER_FP_REG; + } + else + frame->fp_sp_offset = offset; /* Next are the callee-saved GPRs. */ if (frame->mask) { @@ -931,8 +935,10 @@ loongarch_compute_frame_info (void) frame->save_libcall_adjustment = x_save_size; offset += x_save_size; + frame->gp_sp_offset = offset - UNITS_PER_WORD; } - frame->gp_sp_offset = offset - UNITS_PER_WORD; + else + frame->gp_sp_offset = offset; /* The hard frame pointer points above the callee-saved GPRs. */ frame->hard_frame_pointer_offset = offset; /* Above the hard frame pointer is the callee-allocated varags save area. */ diff --git a/gcc/testsuite/gcc.target/loongarch/prolog-opt.c b/gcc/testsuite/gcc.target/loongarch/prolog-opt.c new file mode 100644 index 00000000000..0470a1f1eee --- /dev/null +++ b/gcc/testsuite/gcc.target/loongarch/prolog-opt.c @@ -0,0 +1,15 @@ +/* Test that LoongArch backend stack drop operation optimized. */ + +/* { dg-do compile } */ +/* { dg-options "-O2 -mabi=lp64d" } */ +/* { dg-final { scan-assembler "addi.d\t\\\$r3,\\\$r3,-16" } } */ + +extern int printf (char *, ...); + +int main() +{ + char buf[1024 * 12]; + printf ("%p\n", buf); + return 0; +} +