On Mon, Aug 18, 2025 at 4:50 AM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> We can't place a TLS call before a conditional jump in a basic block like
>
> (code_label 13 11 14 4 2 (nil) [1 uses])
> (note 14 13 16 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
> (jump_insn 16 14 17 4 (set (pc)
> (if_then_else (le (reg:CCNO 17 flags)
> (const_int 0 [0]))
> (label_ref 27)
> (pc))) "x.c":10:21 discrim 1 1462 {*jcc}
> (expr_list:REG_DEAD (reg:CCNO 17 flags)
> (int_list:REG_BR_PROB 628353713 (nil)))
> -> 27)
>
> since the TLS call will clobber flags register nor place a TLS call in a
> basic block if any live caller-saved registers aren't dead at the end of
> the basic block:
>
> ;; live in 6 [bp] 7 [sp] 16 [argp] 17 [flags] 19 [frame] 104
> ;; live gen 0 [ax] 102 106 108 116 117 118 120
> ;; live kill 5 [di]
>
> Instead, we should place such call before all register setting basic
> blocks which dominate the current basic block.
>
> Keep track the replaced GNU and GNU2 TLS instructions. Use these info to
> place the __tls_get_addr call and mark FLAGS register as dead.
>
> gcc/
>
> PR target/121572
> * config/i386/i386-features.cc (replace_tls_call): Add a bitmap
> argument and put the updated TLS instruction in the bitmap.
> (ix86_get_dominator_for_reg): New.
> (ix86_place_single_tls_call): Add 2 bitmap arguments for updated
> GNU and GNU2 TLS instructions. Add the live flag register to the
> bitmap. Insert the __tls_get_addr call before INSN if it replaces
> a __tls_get_addr call. Mark FLAGS register as dead if INSN
> replaced the GNU2 TLS instruction. Clear the live register bitmap
> only for hard register. If there is a conditional jump in the
> basic block or any live caller-saved registers aren't dead at the
> end of the basic block, get the basic block which dominates all
> basic blocks which set the live registers.
>
> gcc/testsuite/
>
> PR target/121572
> * gcc.target/i386/pr121572-1a.c: New test.
> * gcc.target/i386/pr121572-1b.c: Likewise.
> * gcc.target/i386/pr121572-2a.c: Likewise.
> * gcc.target/i386/pr121572-2b.c: Likewise.
>
> Signed-off-by: H.J. Lu <hjl.to...@gmail.com>
> ---
> gcc/config/i386/i386-features.cc | 136 ++++++++++++++++----
> gcc/testsuite/gcc.target/i386/pr121572-1a.c | 41 ++++++
> gcc/testsuite/gcc.target/i386/pr121572-1b.c | 18 +++
> gcc/testsuite/gcc.target/i386/pr121572-2a.c | 39 ++++++
> gcc/testsuite/gcc.target/i386/pr121572-2b.c | 6 +
> 5 files changed, 215 insertions(+), 25 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr121572-1a.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr121572-1b.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr121572-2a.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr121572-2b.c
>
> diff --git a/gcc/config/i386/i386-features.cc
> b/gcc/config/i386/i386-features.cc
> index f0bdc5c1880..903f2b0b478 100644
> --- a/gcc/config/i386/i386-features.cc
> +++ b/gcc/config/i386/i386-features.cc
> @@ -3684,10 +3684,12 @@ ix86_broadcast_inner (rtx op, machine_mode mode,
> return op;
> }
>
> -/* Replace CALL instruction in TLS_CALL_INSNS with SET from SRC. */
> +/* Replace CALL instruction in TLS_CALL_INSNS with SET from SRC and
> + put the updated instruction in UPDATED_TLS_INSNS. */
>
> static void
> -replace_tls_call (rtx src, auto_bitmap &tls_call_insns)
> +replace_tls_call (rtx src, auto_bitmap &tls_call_insns,
> + auto_bitmap &updated_tls_insns)
> {
> bitmap_iterator bi;
> unsigned int id;
> @@ -3716,6 +3718,9 @@ replace_tls_call (rtx src, auto_bitmap &tls_call_insns)
> if (recog_memoized (set_insn) < 0)
> gcc_unreachable ();
>
> + /* Put SET_INSN in UPDATED_TLS_INSNS. */
> + bitmap_set_bit (updated_tls_insns, INSN_UID (set_insn));
> +
> if (dump_file)
> {
> fprintf (dump_file, "\nReplace:\n\n");
> @@ -3732,15 +3737,48 @@ replace_tls_call (rtx src, auto_bitmap
> &tls_call_insns)
> }
> }
>
> +/* Return the basic block which dominates all basic blocks which set
> + hard register REGNO used in basic block BB. */
> +
> +static basic_block
> +ix86_get_dominator_for_reg (unsigned int regno, basic_block bb)
> +{
> + basic_block set_bb;
> + auto_bitmap set_bbs;
> +
> + /* Get all BBs which set REGNO and dominate the current BB from all
> + DEFs of REGNO. */
> + for (df_ref def = DF_REG_DEF_CHAIN (regno);
> + def;
> + def = DF_REF_NEXT_REG (def))
> + if (!DF_REF_IS_ARTIFICIAL (def)
> + && !DF_REF_FLAGS_IS_SET (def, DF_REF_MAY_CLOBBER)
> + && !DF_REF_FLAGS_IS_SET (def, DF_REF_MUST_CLOBBER))
> + {
> + set_bb = DF_REF_BB (def);
> + if (dominated_by_p (CDI_DOMINATORS, bb, set_bb))
> + bitmap_set_bit (set_bbs, set_bb->index);
> + }
> +
> + bb = nearest_common_dominator_for_set (CDI_DOMINATORS, set_bbs);
> + return bb;
> +}
> +
> /* Generate a TLS call of KIND with VAL and copy the call result to DEST,
> at entry of the nearest dominator for basic block map BBS, which is in
> the fake loop that contains the whole function, so that there is only
> - a single TLS CALL of KIND with VAL in the whole function. If
> - TLSDESC_SET isn't nullptr, insert it before the TLS call. */
> + a single TLS CALL of KIND with VAL in the whole function.
> + UPDATED_GNU_TLS_INSNS contains instructions which replace the GNU TLS
> + instructions. UPDATED_GNU2_TLS_INSNS contains instructions which
> + replace the GNU2 TLS instructions. If TLSDESC_SET isn't nullptr,
> + insert it before the TLS call. */
>
> static void
> ix86_place_single_tls_call (rtx dest, rtx val, x86_cse_kind kind,
> - bitmap bbs, rtx tlsdesc_set = nullptr)
> + auto_bitmap &bbs,
> + auto_bitmap &updated_gnu_tls_insns,
> + auto_bitmap &updated_gnu2_tls_insns,
> + rtx tlsdesc_set = nullptr)
> {
> basic_block bb = nearest_common_dominator_for_set (CDI_DOMINATORS, bbs);
> while (bb->loop_father->latch
> @@ -3748,6 +3786,7 @@ ix86_place_single_tls_call (rtx dest, rtx val,
> x86_cse_kind kind,
> bb = get_immediate_dominator (CDI_DOMINATORS,
> bb->loop_father->header);
>
> +place_tls_call:
> rtx_insn *insn = BB_HEAD (bb);
> while (insn && !NONDEBUG_INSN_P (insn))
> {
> @@ -3824,7 +3863,8 @@ ix86_place_single_tls_call (rtx dest, rtx val,
> x86_cse_kind kind,
> auto_bitmap live_caller_saved_regs;
> bitmap in = df_live ? DF_LIVE_IN (bb) : DF_LR_IN (bb);
>
> - bool flags_live_p = bitmap_bit_p (in, FLAGS_REG);
> + if (bitmap_bit_p (in, FLAGS_REG))
> + bitmap_set_bit (live_caller_saved_regs, FLAGS_REG);
>
> unsigned int i;
>
> @@ -3845,13 +3885,46 @@ ix86_place_single_tls_call (rtx dest, rtx val,
> x86_cse_kind kind,
> if (!NONDEBUG_INSN_P (insn))
> continue;
>
> + if (JUMP_P (insn))
> + {
> + /* This must be a conditional jump. */
> + rtx label = JUMP_LABEL (insn);
> + if (label == nullptr
> + || ANY_RETURN_P (label)
> + || !(LABEL_P (label) || SYMBOL_REF_P (label)))
> + gcc_unreachable ();
> +
> + /* Place the call before all FLAGS_REG setting BBs since
> + we can't place a call before nor after a conditional
> + jump. */
> + bb = ix86_get_dominator_for_reg (FLAGS_REG, bb);
> + goto place_tls_call;
Can we put those codes related to find the **BEFORE/AFTER** into a
function and called it recursively(or iteratively to decide find the
final BEFORE/AFTER)
So we can avoid those GOTO statements.
i.e
switch (kind)
{
...
}
ix86_place_single_tls_call_place (....)
if (before)
emit_insn_before (..);
else if (after)
emit_insn_after (...);
else
gcc_unreachable ();
....
> + }
> +
> /* Check if FLAGS register is live. */
> set = single_set (insn);
> if (set)
> {
> rtx dest = SET_DEST (set);
> - if (REG_P (dest) && REGNO (dest) == FLAGS_REG)
> - flags_live_p = true;
> + if (REG_P (dest))
> + {
> + if (bitmap_bit_p (updated_gnu_tls_insns,
> + INSN_UID (insn)))
> + {
> + /* Insert the __tls_get_addr call before INSN which
> + replaces a __tls_get_addr call. */
> + before = insn;
> + goto insert_before;
> + }
> + if (bitmap_bit_p (updated_gnu2_tls_insns,
> + INSN_UID (insn)))
> + /* Mark FLAGS register as dead since FLAGS register
> + would be clobbered by the GNU2 TLS instruction. */
> + bitmap_clear_bit (live_caller_saved_regs,
> + FLAGS_REG);
> + else if (REGNO (dest) == FLAGS_REG)
> + bitmap_set_bit (live_caller_saved_regs, FLAGS_REG);
> + }
> }
>
> rtx link;
> @@ -3863,29 +3936,30 @@ ix86_place_single_tls_call (rtx dest, rtx val,
> x86_cse_kind kind,
> for (i = REGNO (XEXP (link, 0));
> i < END_REGNO (XEXP (link, 0));
> i++)
> - bitmap_clear_bit (live_caller_saved_regs, i);
> -
> - /* Check if FLAGS register is dead. */
> - if (REGNO (XEXP (link, 0)) == FLAGS_REG)
> - flags_live_p = false;
> + if (i < FIRST_PSEUDO_REGISTER)
> + bitmap_clear_bit (live_caller_saved_regs, i);
>
> if (bitmap_empty_p (live_caller_saved_regs))
> {
> - /* All live caller-saved registers are dead after
> - this instruction. Since TLS instructions
> - clobber FLAGS register, it must be dead where
> - the TLS will be inserted after. */
> - if (flags_live_p)
> - gcc_unreachable ();
> after = insn;
> goto insert_after;
> }
> }
> }
>
> - /* All live caller-saved registers should be dead at the end
> - of this basic block. */
> - gcc_unreachable ();
> + /* If any live caller-saved registers aren't dead at the end
> + of this basic block, get the basic block which dominates all
> + basic blocks which set the remaining live registers. */
> + auto_bitmap set_bbs;
> + bitmap_iterator bi;
> + unsigned int id;
> + EXECUTE_IF_SET_IN_BITMAP (live_caller_saved_regs, 0, id, bi)
> + {
> + basic_block set_bb = ix86_get_dominator_for_reg (id, bb);
> + bitmap_set_bit (set_bbs, set_bb->index);
> + }
> + bb = nearest_common_dominator_for_set (CDI_DOMINATORS, set_bbs);
> + goto place_tls_call;
> }
>
> /* Emit the TLS CALL insn. */
> @@ -3895,7 +3969,10 @@ insert_after:
> tls_insn = emit_insn_after (tls, after);
> }
> else
> - tls_insn = emit_insn_before (tls, before);
> + {
> +insert_before:
> + tls_insn = emit_insn_before (tls, before);
> + }
>
> rtx_insn *tlsdesc_insn = nullptr;
> if (tlsdesc_set)
> @@ -4213,6 +4290,8 @@ pass_x86_cse::x86_cse (void)
> basic_block bb;
> rtx_insn *insn;
> unsigned int i;
> + auto_bitmap updated_gnu_tls_insns;
> + auto_bitmap updated_gnu2_tls_insns;
>
> df_set_flags (DF_DEFER_INSN_RESCAN);
>
> @@ -4333,7 +4412,10 @@ pass_x86_cse::x86_cse (void)
> case X86_CSE_TLS_LD_BASE:
> case X86_CSE_TLSDESC:
> broadcast_reg = gen_reg_rtx (load->mode);
> - replace_tls_call (broadcast_reg, load->insns);
> + replace_tls_call (broadcast_reg, load->insns,
> + (load->kind == X86_CSE_TLSDESC
> + ? updated_gnu2_tls_insns
> + : updated_gnu_tls_insns));
> load->broadcast_reg = broadcast_reg;
> break;
>
> @@ -4399,6 +4481,8 @@ pass_x86_cse::x86_cse (void)
> load->val,
> load->kind,
> load->bbs,
> + updated_gnu_tls_insns,
> + updated_gnu2_tls_insns,
> PATTERN (load->def_insn));
> break;
> case X86_CSE_VEC_DUP:
> @@ -4442,7 +4526,9 @@ pass_x86_cse::x86_cse (void)
> ix86_place_single_tls_call (load->broadcast_reg,
> load->val,
> load->kind,
> - load->bbs);
> + load->bbs,
> + updated_gnu_tls_insns,
> + updated_gnu2_tls_insns);
> break;
> case X86_CSE_CONST0_VECTOR:
> case X86_CSE_CONSTM1_VECTOR:
> diff --git a/gcc/testsuite/gcc.target/i386/pr121572-1a.c
> b/gcc/testsuite/gcc.target/i386/pr121572-1a.c
> new file mode 100644
> index 00000000000..270d8ff5cb6
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr121572-1a.c
> @@ -0,0 +1,41 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O0 -fpic -fplt -mtls-dialect=gnu" } */
> +/* Keep labels and directives ('.cfi_startproc', '.cfi_endproc'). */
> +/* { dg-final { check-function-bodies "**" "" "" { target { ! ia32 } }
> {^\t?\.} } } */
> +
> +/*
> +**bug:
> +**.LFB[0-9]+:
> +**...
> +** leaq tv_cache@tlsld\(%rip\), %rdi
> +** call __tls_get_addr@PLT
> +** movl \$-1, %edi
> +** mov[l|q] %[e|r]ax, %[e|r]bx
> +** call val@PLT
> +**...
> +*/
> +
> +extern __thread int tv_cache __attribute__ ((visibility ("hidden")));
> +extern void use_cache (int);
> +extern int val (int v);
> +
> +__attribute__ ((optimize (2)))
> +void
> +bug (void)
> +{
> + int compared = val (-1);
> +
> + if (compared == 0 || (compared > 0 && val (2) == 0))
> + {
> + __builtin_trap ();
> + }
> +
> + if (compared < 0)
> + {
> + use_cache (tv_cache);
> + return;
> + }
> +
> + use_cache (tv_cache);
> + __builtin_trap ();
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr121572-1b.c
> b/gcc/testsuite/gcc.target/i386/pr121572-1b.c
> new file mode 100644
> index 00000000000..8a6089109f5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr121572-1b.c
> @@ -0,0 +1,18 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O0 -fpic -fplt -mtls-dialect=gnu2" } */
> +/* Keep labels and directives ('.cfi_startproc', '.cfi_endproc'). */
> +/* { dg-final { check-function-bodies "**" "" "" { target { ! ia32 } }
> {^\t?\.} } } */
> +
> +/*
> +**bug:
> +**.LFB[0-9]+:
> +**...
> +** lea[l|q] tv_cache@TLSDESC\(%rip\), %[e|r]ax
> +** movl \$-1, %edi
> +** call \*tv_cache@TLSCALL\(%[e|r]ax\)
> +** mov[l|q] %[e|r]ax, %[e|r]bx
> +** call val@PLT
> +**...
> +*/
> +
> +#include "pr121572-1a.c"
> diff --git a/gcc/testsuite/gcc.target/i386/pr121572-2a.c
> b/gcc/testsuite/gcc.target/i386/pr121572-2a.c
> new file mode 100644
> index 00000000000..38b254657d3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr121572-2a.c
> @@ -0,0 +1,39 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpic -fplt -mtls-dialect=gnu" } */
> +
> +typedef enum
> +{
> + MPFR_RNDN
> +} mpfr_rnd_t;
> +typedef int mpfr_t[1];
> +long __gmpfr_emin, mpfr_agm_expo_0;
> +_Thread_local long __gmpfr_emax;
> +int mpfr_agm_compare, mpfr_agm___trans_tmp_1;
> +mpfr_t mpfr_agm_u;
> +void mpfr_mul (int *, int, int, mpfr_rnd_t);
> +int
> +mpfr_agm (int op1)
> +{
> + int op2 = 0;
> + if (__builtin_expect (mpfr_agm_compare == 0, 0))
> + return 0;
> + if (mpfr_agm_compare > 0)
> + {
> + int t = op1;
> + op2 = t;
> + }
> + mpfr_agm_expo_0 = __gmpfr_emax;
> + for (;;)
> + {
> + retry:
> + mpfr_mul (mpfr_agm_u, op1, op2, MPFR_RNDN);
> + if (0)
> + goto retry;
> + if (__builtin_expect (mpfr_agm___trans_tmp_1, 1))
> + break;
> + }
> + __gmpfr_emin = __gmpfr_emax;
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-times "call\[ \t\]__tls_get_addr@PLT" 1 {
> target { ! ia32 } } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr121572-2b.c
> b/gcc/testsuite/gcc.target/i386/pr121572-2b.c
> new file mode 100644
> index 00000000000..33d70024324
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr121572-2b.c
> @@ -0,0 +1,6 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpic -fplt -mtls-dialect=gnu2" } */
> +
> +#include "pr121572-2a.c"
> +
> +/* { dg-final { scan-assembler-times "call\[
> \t\]\\*__gmpfr_emax@TLSCALL\\(%(?:r|e)ax\\)" 1 { target { ! ia32 } } } } */
> --
> 2.50.1
>
--
BR,
Hongtao
