https://gcc.gnu.org/g:5c1f506d4515864bd38f95f82dff624318327788
commit r16-4639-g5c1f506d4515864bd38f95f82dff624318327788 Author: Takayuki 'January June' Suwa <[email protected]> Date: Mon Oct 27 06:32:09 2025 +0900 xtensa: Revert "xtensa: Make one_cmplsi2 optimizer-friendly" This patch effectively revert the past commit 9777d446e2148ef9a6e9f35db3f4eab99ee8812c. Almost the only reason we committed that was because some optimizers in the RTL ifcvt pass needed '(set (reg) (not (reg)))' RTX, however, in recent versions of gcc, the equivalent optimizations are performed before RTL passes, so the need for that commit has all but disappeared. /* example 1 */ int test0(int a) { return a < 0 ? ~a : a; } ;; result 1 test0: entry sp, 32 srai a8, a2, 31 ;; If-conversion before RTL expansion xor a2, a8, a2 retw.n Instead, expanding it to an XOR with a pseudo whose value of -1 early in the RTL passes will take advantage of CSE, forward propagation, or loop- invariant hoisting. /* example 2 */ long long test1(long long a) { return ~a; } void test2(int a[]) { int i; for (i = 0; i < 16; ++i) a[i] = ~a[i]; } ;; result 2 test1: entry sp, 32 movi.n a8, -1 ;; consolidated by CSE xor a2, a2, a8 xor a3, a3, a8 retw.n test2: entry sp, 32 movi.n a10, -1 ;; hoisted out movi.n a9, 0x10 loop a9, .L5_LEND .L5: l32i.n a8, a2, 0 xor a8, a8, a10 s32i.n a8, a2, 0 addi.n a2, a2, 4 .L5_LEND: retw.n Another concern with reverting that commit is the impact on complex insns that have '(not)' as part of them, but also nothing to worry about; because the RTL insn combiner can correctly recognize an XOR with a register value of -1 as a one's complement operation even without such RTX, and apply the result to subsequent combine operations. gcc/ChangeLog: * config/xtensa/xtensa.md (one_cmplsi2): Rearrange back as an expand pattern. gcc/testsuite/ChangeLog: * gcc.target/xtensa/one_cmpl_abs.c: Remove. Diff: --- gcc/config/xtensa/xtensa.md | 25 +++++++------------------ gcc/testsuite/gcc.target/xtensa/one_cmpl_abs.c | 9 --------- 2 files changed, 7 insertions(+), 27 deletions(-) diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md index 374288df7083..4ba7f54c9408 100644 --- a/gcc/config/xtensa/xtensa.md +++ b/gcc/config/xtensa/xtensa.md @@ -680,26 +680,15 @@ (set_attr "mode" "SI") (set_attr "length" "3")]) -(define_insn_and_split "one_cmplsi2" - [(set (match_operand:SI 0 "register_operand" "=a") - (not:SI (match_operand:SI 1 "register_operand" "r")))] +(define_expand "one_cmplsi2" + [(set (match_operand:SI 0 "register_operand") + (not:SI (match_operand:SI 1 "register_operand")))] "" - "#" - "&& can_create_pseudo_p ()" - [(set (match_dup 2) - (const_int -1)) - (set (match_dup 0) - (xor:SI (match_dup 1) - (match_dup 2)))] { - operands[2] = gen_reg_rtx (SImode); -} - [(set_attr "type" "arith") - (set_attr "mode" "SI") - (set (attr "length") - (if_then_else (match_test "TARGET_DENSITY") - (const_int 5) - (const_int 6)))]) + emit_insn (gen_xorsi3 (operands[0], operands[1], + force_reg (SImode, constm1_rtx))); + DONE; +}) (define_insn "negsf2" [(set (match_operand:SF 0 "register_operand" "=f") diff --git a/gcc/testsuite/gcc.target/xtensa/one_cmpl_abs.c b/gcc/testsuite/gcc.target/xtensa/one_cmpl_abs.c deleted file mode 100644 index 608f65fd7774..000000000000 --- a/gcc/testsuite/gcc.target/xtensa/one_cmpl_abs.c +++ /dev/null @@ -1,9 +0,0 @@ -/* { dg-do compile } */ -/* { dg-options "-O1" } */ - -int one_cmpl_abs(int a) -{ - return a < 0 ? ~a : a; -} - -/* { dg-final { scan-assembler-not "bgez" } } */
