https://gcc.gnu.org/g:673f17a48cbbc4f7f9881cb35b43e9b96994efae
commit r15-10844-g673f17a48cbbc4f7f9881cb35b43e9b96994efae Author: Vladimir N. Makarov <[email protected]> Date: Wed Jan 28 10:52:21 2026 -0500 [PR121571, LRA]: Reprocess asm insn with different preferences when there are no enough regs for the asm-insn The test for the PR contains asm insn requiring 7 general regs but three operands can be in memory too ('g' constraint). There are only 6 available general regs. IRA in the test case assigns a mask reg to one pseudo. When LRA reloads the pseudo assigned to mask reg, it frees general reg assigned to another pseudo in the asm and assigns mask reg to another pseudo. After a few iterations, we have asm all operands of which are reload pseudos assigned to general regs and one pseudo assigned to mask reg. After that LRA can do nothing and reports "not enough regs". The patch recognizes situation when there are not enough regs for an asm insn and makes 2nd attempt to find reloads when memory for operands with 'g' or 'rm' constraint is preferred. gcc/ChangeLog: PR target/121571 * lra-constraints.cc (process_alt_operands): Reprocess asm insn when there are no enough regs for the asm-insn. gcc/testsuite/ChangeLog: PR target/121571 * gcc.target/i386/pr121571.c: New. Diff: --- gcc/lra-constraints.cc | 26 +++++++++++++++++++++++++- gcc/testsuite/gcc.target/i386/pr121571.c | 14 ++++++++++++++ 2 files changed, 39 insertions(+), 1 deletion(-) diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc index 2c477d1688eb..e00167acba3a 100644 --- a/gcc/lra-constraints.cc +++ b/gcc/lra-constraints.cc @@ -2217,6 +2217,8 @@ process_alt_operands (int only_alternative) if (only_alternative >= 0) preferred &= ALTERNATIVE_BIT (only_alternative); + bool prefer_memory_p = false; + repeat: for (nalt = 0; nalt < n_alternatives; nalt++) { /* Loop over operands for one constraint alternative. */ @@ -2549,6 +2551,11 @@ process_alt_operands (int only_alternative) || general_constant_p (op) || spilled_pseudo_p (op)) win = true; + if (REG_P (op) && prefer_memory_p) + { + badop = false; + offmemok = true; + } cl = GENERAL_REGS; cl_filter = nullptr; goto reg; @@ -2665,7 +2672,7 @@ process_alt_operands (int only_alternative) (this_alternative_exclude_start_hard_regs, hard_regno[nop])))) win = true; - else if (hard_regno[nop] < 0) + else if (hard_regno[nop] < 0 && !prefer_memory_p) { if (in_class_p (op, this_alternative, NULL)) win = true; @@ -2767,6 +2774,12 @@ process_alt_operands (int only_alternative) this_alternative_match_win = true; else { + if (prefer_memory_p && offmemok) + { + winreg = false; + this_alternative = NO_REGS; + } + int const_to_mem = 0; bool no_regs_p; @@ -3300,6 +3313,17 @@ process_alt_operands (int only_alternative) ira_class_hard_regs_num[all_this_alternative], all_used_nregs, all_reload_nregs); overall += LRA_MAX_REJECT; + if (!prefer_memory_p && INSN_CODE (curr_insn) < 0) + { + /* asm can permit memory and reg and can be not enough regs for + asm -- try now memory: */ + prefer_memory_p = true; + if (lra_dump_file != NULL) + fprintf + (lra_dump_file, + " Trying now memory for operands\n"); + goto repeat; + } } ok_p = true; curr_alt_dont_inherit_ops_num = 0; diff --git a/gcc/testsuite/gcc.target/i386/pr121571.c b/gcc/testsuite/gcc.target/i386/pr121571.c new file mode 100644 index 000000000000..5be170ed7b26 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr121571.c @@ -0,0 +1,14 @@ +/* { dg-do compile } */ +/* { dg-options "-march=skylake-avx512 -Os" } */ + +int a, b, c, d, e, f; + +void +foo () +{ + int g[2] = { e, f }; + if ((g[0] | g[1]) != 0) + __asm__ ("" + : "=r" (d), "=&r" (c), "=&r" (b), "=&r" (a) + : "0" (0), "g" (g), "g" (g[1]), "g" (g[0])); +}
