This patch doesn't work. But the first one is okay, despite that it pessimizes
sin and cos calls by skipping the optimization pass.
Sep 18, 2025 11:04:16 PM Peter Damianov <peter0...@disroot.org>:
> In my previous patch, I disabled pass_cse_sincos for -fmath-errno. This was
> because it was causing ICEs when trying to replace sin/cos calls, and more
> importantly, the pass was transforming sin+cos to cexpi which doesn't set
> errno like sin/cos do. The optimization is valid when either:
> 1. We don't care about errno (-fno-math-errno), or
> 2. We can use sincos() which does set errno like sin/cos do
>
> This patch fixes the ICE and implements a different optimization strategy
> that preserves errno semantics by directly calling sincos when available,
> and only falling back to cexpi when errno doesn't matter. The ICEs are
> resolved by properly unlinking VDEFs before statement replacement.
>
> gcc/ChangeLog:
>
> PR tree-optimization/80042
> * tree-ssa-math-opts.cc (execute_cse_sincos_1): Optimize to sincos
> for -fmath-errno. Fix ICE with unlink_stmt_vdef before gsi_replace.
> (pass_cse_sincos::execute): Remove errno check to allow proper
> optimization in execute_cse_sincos_1.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/80042
> * gcc.dg/pr80042.c: New test.
> ---
> gcc/testsuite/gcc.dg/pr80042.c | 71 +++++++++++++++++++++
> gcc/tree-ssa-math-opts.cc | 110 ++++++++++++++++++++++++++-------
> 2 files changed, 159 insertions(+), 22 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/pr80042.c
>
> diff --git a/gcc/testsuite/gcc.dg/pr80042.c b/gcc/testsuite/gcc.dg/pr80042.c
> new file mode 100644
> index 00000000000..7843604d23c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr80042.c
> @@ -0,0 +1,71 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -lm -fmath-errno" } */
> +
> +#include <errno.h>
> +
> +void test_double(void)
> +{
> + double s, c;
> +
> + errno = 0;
> + s = __builtin_sin(__builtin_inf());
> + if (errno != EDOM)
> + __builtin_abort();
> +
> + errno = 0;
> + c = __builtin_cos(__builtin_inf());
> + if (errno != EDOM)
> + __builtin_abort();
> +
> + errno = 0;
> + __builtin_sincos(__builtin_inf(), &s, &c);
> + if (errno != EDOM)
> + __builtin_abort();
> +}
> +
> +void test_float(void)
> +{
> + float s, c;
> +
> + errno = 0;
> + s = __builtin_sinf(__builtin_inff());
> + if (errno != EDOM)
> + __builtin_abort();
> +
> + errno = 0;
> + c = __builtin_cosf(__builtin_inff());
> + if (errno != EDOM)
> + __builtin_abort();
> +
> + errno = 0;
> + __builtin_sincosf(__builtin_inff(), &s, &c);
> + if (errno != EDOM)
> + __builtin_abort();
> +}
> +
> +void test_longdouble(void)
> +{
> + long double s, c;
> +
> + errno = 0;
> + s = __builtin_sinl(__builtin_infl());
> + if (errno != EDOM)
> + __builtin_abort();
> +
> + errno = 0;
> + c = __builtin_cosl(__builtin_infl());
> + if (errno != EDOM)
> + __builtin_abort();
> +
> + errno = 0;
> + __builtin_sincosl(__builtin_infl(), &s, &c);
> + if (errno != EDOM)
> + __builtin_abort();
> +}
> +
> +int main(void)
> +{
> + test_double();
> + test_float();
> + test_longdouble();
> +}
> \ No newline at end of file
> diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
> index c736709158f..4076bcf55d5 100644
> --- a/gcc/tree-ssa-math-opts.cc
> +++ b/gcc/tree-ssa-math-opts.cc
> @@ -1253,7 +1253,7 @@ execute_cse_sincos_1 (tree name)
> {
> gimple_stmt_iterator gsi;
> imm_use_iterator use_iter;
> - tree fndecl, res, type = NULL_TREE;
> + tree res, type = NULL_TREE;
> gimple *def_stmt, *use_stmt, *stmt;
> int seen_cos = 0, seen_sin = 0, seen_cexpi = 0;
> auto_vec<gimple *> stmts;
> @@ -1302,27 +1302,97 @@ execute_cse_sincos_1 (tree name)
> if (seen_cos + seen_sin + seen_cexpi <= 1)
> return false;
>
> - /* Simply insert cexpi at the beginning of top_bb but not earlier than
> - the name def statement. */
> - fndecl = mathfn_built_in (type, BUILT_IN_CEXPI);
> - if (!fndecl)
> - return false;
> - stmt = gimple_build_call (fndecl, 1, name);
> - res = make_temp_ssa_name (TREE_TYPE (TREE_TYPE (fndecl)), stmt,
> "sincostmp");
> - gimple_call_set_lhs (stmt, res);
> + machine_mode mode = TYPE_MODE (type);
> + tree sincos_fndecl = builtin_decl_explicit (BUILT_IN_SINCOS);
> + bool can_use_sincos = sincos_fndecl
> + && (optab_handler (sincos_optab, mode)
> + != CODE_FOR_nothing
> + || targetm.libc_has_function (function_sincos,
> + type));
>
> - def_stmt = SSA_NAME_DEF_STMT (name);
> - if (!SSA_NAME_IS_DEFAULT_DEF (name)
> - && gimple_code (def_stmt) != GIMPLE_PHI
> - && gimple_bb (def_stmt) == top_bb)
> + if (flag_errno_math && (seen_sin || seen_cos) && !can_use_sincos)
> {
> - gsi = gsi_for_stmt (def_stmt);
> - gsi_insert_after (&gsi, stmt, GSI_SAME_STMT);
> + /* We cannot rewrite sin and cos calls to cexpi if we have
> + flag_errno_math because cexpi does not set errno. */
> + return false;
> + }
> +
> + if (can_use_sincos)
> + {
> + /* Generate sincos call if sincos is available. */
> +
> + tree complex_type = build_complex_type (type);
> +
> + /* Create temporary variables for sin and cos results. */
> + tree sin_result = create_tmp_var (type, "sincos_sin");
> + tree cos_result = create_tmp_var (type, "sincos_cos");
> +
> + /* Create addresses to the temporary variables. */
> + tree sin_addr = build_fold_addr_expr (sin_result);
> + tree cos_addr = build_fold_addr_expr (cos_result);
> +
> + /* Generate sincos (angle, &sin_result, &cos_result) call. */
> + stmt = gimple_build_call (sincos_fndecl, 3, name, sin_addr, cos_addr);
> +
> + /* Insert the sincos call. */
> + def_stmt = SSA_NAME_DEF_STMT (name);
> + if (!SSA_NAME_IS_DEFAULT_DEF (name)
> + && gimple_code (def_stmt) != GIMPLE_PHI
> + && gimple_bb (def_stmt) == top_bb)
> + {
> + gsi = gsi_for_stmt (def_stmt);
> + gsi_insert_after (&gsi, stmt, GSI_SAME_STMT);
> + }
> + else
> + {
> + gsi = gsi_after_labels (top_bb);
> + gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
> + }
> +
> + /* Create SSA names for the results and load them from temporaries. */
> + tree sin_ssa = make_ssa_name (type);
> + tree cos_ssa = make_ssa_name (type);
> +
> + gimple *sin_load = gimple_build_assign (sin_ssa, sin_result);
> + gimple *cos_load = gimple_build_assign (cos_ssa, cos_result);
> +
> + gsi_insert_after (&gsi, sin_load, GSI_NEW_STMT);
> + gsi_insert_after (&gsi, cos_load, GSI_NEW_STMT);
> +
> + /* Create a complex number from sin and cos results so the replacement
> + logic can extract them using REALPART_EXPR (cos) and
> + IMAGPART_EXPR (sin). */
> + res = make_temp_ssa_name (complex_type, NULL, "sincostmp");
> + gimple *complex_stmt = gimple_build_assign (res, COMPLEX_EXPR, cos_ssa,
> + sin_ssa);
> + gsi_insert_after (&gsi, complex_stmt, GSI_NEW_STMT);
> }
> else
> {
> - gsi = gsi_after_labels (top_bb);
> - gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
> + cexpi_fndecl = mathfn_built_in (type, BUILT_IN_CEXPI);
> + if (!cexpi_fndecl)
> + return false;
> +
> + /* Generate a call to cexpi instead - this is fine if we don't care
> + about errno. */
> + stmt = gimple_build_call (cexpi_fndecl, 1, name);
> + res = make_temp_ssa_name (TREE_TYPE (TREE_TYPE (cexpi_fndecl)), stmt,
> + "sincostmp");
> + gimple_call_set_lhs (stmt, res);
> +
> + def_stmt = SSA_NAME_DEF_STMT (name);
> + if (!SSA_NAME_IS_DEFAULT_DEF (name)
> + && gimple_code (def_stmt) != GIMPLE_PHI
> + && gimple_bb (def_stmt) == top_bb)
> + {
> + gsi = gsi_for_stmt (def_stmt);
> + gsi_insert_after (&gsi, stmt, GSI_SAME_STMT);
> + }
> + else
> + {
> + gsi = gsi_after_labels (top_bb);
> + gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
> + }
> }
> sincos_stats.inserted++;
>
> @@ -1353,6 +1423,7 @@ execute_cse_sincos_1 (tree name)
> stmt = gimple_build_assign (gimple_call_lhs (use_stmt), rhs);
>
> gsi = gsi_for_stmt (use_stmt);
> + unlink_stmt_vdef (use_stmt);
> gsi_replace (&gsi, stmt, true);
> if (gimple_purge_dead_eh_edges (gimple_bb (stmt)))
> cfg_changed = true;
> @@ -2239,11 +2310,6 @@ pass_cse_sincos::execute (function *fun)
> {
> CASE_CFN_COS:
> CASE_CFN_SIN:
> - /* Don't optimize sin/cos to cexpi if errno semantics matter,
> - since cexpi doesn't set errno like sin/cos can. */
> - if (flag_errno_math)
> - break;
> - gcc_fallthrough ();
> CASE_CFN_CEXPI:
> arg = gimple_call_arg (stmt, 0);
> /* Make sure we have either sincos or cexp. */
> --
> 2.39.5
