https://gcc.gnu.org/g:7b39d7b3b84d4d098b51bbdbd15e6ddea6bf99db
commit r16-8516-g7b39d7b3b84d4d098b51bbdbd15e6ddea6bf99db Author: H.J. Lu <[email protected]> Date: Fri Apr 3 15:55:17 2026 +0800 Correct x86: Call ix86_access_stack_p only for larger alignment commit f511bf93f947199a9f9099fee87b7052e5515fb9 Author: H.J. Lu <[email protected]> Date: Sun Mar 29 14:30:28 2026 -0700 x86: Call ix86_access_stack_p only for larger alignment has 2 issues: 1. It didn't exclude memory with SYMBOLIC_CONST when checking for stack access. 2. It replaced: HARD_REG_SET hard_stack_slot_access = stack_slot_access; ... bool symbolic_const_load_p = false; if (!TEST_HARD_REG_BIT (hard_stack_slot_access, regno)) ... symbolic_const_load_p = true; ... if (!symbolic_const_load_p || ix86_access_stack_p...) call ix86_update_stack_alignment. with if (ix86_need_alignment_p... && ix86_access_stack_p...) call ix86_update_stack_alignment. Since ix86_access_stack_p excludes registers on hard_stack_slot_access, stack alignment isn't updated for registers on hard_stack_slot_access. Instead, we should do if (ix86_need_alignment_p... && (TEST_HARD_REG_BIT (hard_stack_slot_access, regno) || ix86_access_stack_p...)) call ix86_update_stack_alignment. The compile times of PR target/124165 and PR target/124684 test are unchanged. if (ix86_need_alignment_p... && (TEST_HARD_REG_BIT (hard_stack_slot_access, regno) || ix86_access_stack_p...)) call ix86_update_stack_alignment. gcc/ PR target/124759 PR target/124789 * config/i386/i386.cc (ix86_need_alignment_p_2): New function. Exclude memory with SYMBOLIC_CONST. (ix86_need_alignment_p_1): Call ix86_need_alignment_p_2. (ix86_find_max_used_stack_alignment): Restore hard_stack_slot_access handling. gcc/testsuite/ PR target/124759 PR target/124789 * gcc.target/i386/pr124759.c: New test. Signed-off-by: H.J. Lu <[email protected]> Diff: --- gcc/config/i386/i386.cc | 40 +++++++++++++++++++++++++++----- gcc/testsuite/gcc.target/i386/pr124759.c | 29 +++++++++++++++++++++++ 2 files changed, 63 insertions(+), 6 deletions(-) diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index f4d0f6239433..9d1a2af70647 100644 --- a/gcc/config/i386/i386.cc +++ b/gcc/config/i386/i386.cc @@ -8781,6 +8781,29 @@ ix86_access_stack_p (unsigned int regno, basic_block bb, return false; } +/* Return true if OP isn't a memory operand with SYMBOLIC_CONST and + needs alignment > ALIGNMENT. */ + +static bool +ix86_need_alignment_p_2 (const_rtx op, unsigned int alignment) +{ + bool need_alignment = MEM_ALIGN (op) > alignment; + tree mem_expr = MEM_EXPR (op); + if (!mem_expr) + return need_alignment; + + tree var = get_base_address (mem_expr); + if (!VAR_P (var) || !DECL_RTL_SET_P (var)) + return need_alignment; + + rtx x = DECL_RTL (var); + if (!MEM_P (x)) + return need_alignment; + + x = XEXP (x, 0); + return !SYMBOLIC_CONST (x) && need_alignment; +} + /* Return true if SET needs alignment > ALIGNMENT. */ static bool @@ -8789,7 +8812,7 @@ ix86_need_alignment_p_1 (rtx set, unsigned int alignment) rtx dest = SET_DEST (set); if (MEM_P (dest)) - return MEM_ALIGN (dest) > alignment; + return ix86_need_alignment_p_2 (dest, alignment); const_rtx src = SET_SRC (set); @@ -8799,7 +8822,7 @@ ix86_need_alignment_p_1 (rtx set, unsigned int alignment) auto op = *iter; if (MEM_P (op)) - return MEM_ALIGN (op) > alignment; + return ix86_need_alignment_p_2 (op, alignment); } return false; @@ -8890,6 +8913,9 @@ ix86_find_max_used_stack_alignment (unsigned int &stack_alignment, bitmap_set_bit (worklist, HARD_FRAME_POINTER_REGNUM); } + /* Registers on HARD_STACK_SLOT_ACCESS always access stack. */ + HARD_REG_SET hard_stack_slot_access = stack_slot_access; + calculate_dominance_info (CDI_DOMINATORS); unsigned int regno; @@ -8926,10 +8952,12 @@ ix86_find_max_used_stack_alignment (unsigned int &stack_alignment, /* Call ix86_access_stack_p only if INSN needs alignment > STACK_ALIGNMENT. */ if (ix86_need_alignment_p (insn, stack_alignment) - && ix86_access_stack_p (regno, BLOCK_FOR_INSN (insn), - set_up_by_prologue, prologue_used, - reg_dominate_bbs_known, - reg_dominate_bbs)) + && (TEST_HARD_REG_BIT (hard_stack_slot_access, regno) + || ix86_access_stack_p (regno, BLOCK_FOR_INSN (insn), + set_up_by_prologue, + prologue_used, + reg_dominate_bbs_known, + reg_dominate_bbs))) { /* Update stack alignment if REGNO is used for stack access. */ diff --git a/gcc/testsuite/gcc.target/i386/pr124759.c b/gcc/testsuite/gcc.target/i386/pr124759.c new file mode 100644 index 000000000000..b5a86b7b9bed --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr124759.c @@ -0,0 +1,29 @@ +/* { dg-do run { target avx_runtime } } */ +/* { dg-options "-fhardened -O3 -mavx" } */ + +struct a { + unsigned long long b; + unsigned long long c; + int d; + char e; + int f; +} g; +int h = 1, i, j; +long long k, l, n; +int m[1]={}; +short o; +static inline short p(short q, short r) { return q + r; } +int main() { + for (; h < 3; h = p(h, 1)) + if (h) { + k |= 4; + struct a s = {8, 2, 2, 4, 15}; + for (int n = 0; n != 54; n++) + if (m[l]) + if (i) + o = 0; + g = s; + j &= 4073709551610LL; + } + return 0; +}
