https://gcc.gnu.org/g:33402b1684a564e4143989dfe377f3e34dac0d13
commit r17-2677-g33402b1684a564e4143989dfe377f3e34dac0d13 Author: Philipp Tomsich <[email protected]> Date: Thu Jul 23 19:09:21 2026 +0200 ifcvt: drop redundant reversibility pre-checks in store-flag callers The PR126347 fix (commit dcb8c8d3e733) made noce_emit_store_flag return NULL_RTX whenever the requested (reversed) comparison code is UNKNOWN, so every caller already copes with an unreversible condition through the existing NULL_RTX return. Remove the redundant guards and document the invariant on noce_emit_store_flag, matching noce_try_store_flag_logical, which already relies on the NULL_RTX return with no pre-check. The noce_reversed_cond_code guards in noce_try_addcc and noce_try_cmove_arith protect a different consumer and are left in place. Bootstrapped and regression tested on x86_64-pc-linux-gnu with no regressions. gcc/ * ifcvt.cc (noce_emit_store_flag): Document that a NULL_RTX return signals an unreversible condition. (noce_try_store_flag): Drop redundant noce_reversed_cond_code pre-check. (noce_try_shifted_store_flag): Likewise. (noce_try_store_flag_constants): Drop redundant can_reverse guards on the reversed 2^n and -1 cases. (noce_try_store_flag_mask): Set reversep unconditionally; the store-flag emission now handles an unreversible condition. Diff: --- gcc/ifcvt.cc | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc index 6b169e69741d..7efea2115f73 100644 --- a/gcc/ifcvt.cc +++ b/gcc/ifcvt.cc @@ -825,7 +825,9 @@ default_noce_conversion_profitable_p (rtx_insn *seq, return speed_p && cost <= if_info->max_seq_cost; } -/* Helper function for noce_try_store_flag*. */ +/* Helper function for noce_try_store_flag*. Return NULL_RTX on failure, + including when REVERSEP is requested but the condition cannot be + reversed; callers may rely on this and need not pre-check. */ static rtx noce_emit_store_flag (struct noce_if_info *if_info, rtx x, bool reversep, @@ -1457,8 +1459,7 @@ noce_try_store_flag (struct noce_if_info *if_info) reversep = false; else if (if_info->b == const0_rtx && CONST_INT_P (if_info->a) - && INTVAL (if_info->a) == STORE_FLAG_VALUE - && noce_reversed_cond_code (if_info) != UNKNOWN) + && INTVAL (if_info->a) == STORE_FLAG_VALUE) reversep = true; else return false; @@ -1619,8 +1620,7 @@ noce_try_shifted_store_flag (struct noce_if_info *if_info) && GET_CODE (b) == REG && rtx_equal_p (XEXP (a, 0), b) && CONST_INT_P (XEXP (a, 1)) - && pow2p_hwi (INTVAL (XEXP (a, 1))) - && noce_reversed_cond_code (if_info) != UNKNOWN) + && pow2p_hwi (INTVAL (XEXP (a, 1)))) { code = GET_CODE (a); common = XEXP (a, 0); @@ -1809,7 +1809,7 @@ noce_try_store_flag_constants (struct noce_if_info *if_info) && STORE_FLAG_VALUE == 1) normalize = 1; /* Is this (cond) ? 0 : 2^n? */ - else if (itrue == 0 && pow2p_hwi (ifalse) && can_reverse + else if (itrue == 0 && pow2p_hwi (ifalse) && STORE_FLAG_VALUE == 1) { normalize = 1; @@ -1820,7 +1820,7 @@ noce_try_store_flag_constants (struct noce_if_info *if_info) && STORE_FLAG_VALUE == -1) normalize = -1; /* Is this (cond) ? x : -1? */ - else if (ifalse == -1 && can_reverse + else if (ifalse == -1 && STORE_FLAG_VALUE == -1) { normalize = -1; @@ -2114,7 +2114,7 @@ noce_try_store_flag_mask (struct noce_if_info *if_info) if ((if_info->a == const0_rtx && (REG_P (if_info->b) || rtx_equal_p (if_info->b, if_info->x))) - || ((reversep = (noce_reversed_cond_code (if_info) != UNKNOWN)) + || ((reversep = true) && if_info->b == const0_rtx && (REG_P (if_info->a) || rtx_equal_p (if_info->a, if_info->x)))) {
