https://gcc.gnu.org/g:89e6b4902e850d350ead6f11eaf4dd6a98b8c715
commit r14-12343-g89e6b4902e850d350ead6f11eaf4dd6a98b8c715 Author: Xi Ruoyao <[email protected]> Date: Thu Feb 26 11:55:22 2026 +0800 middle-end: extend the narrower shift amount before broadcasting it [PR 124250] The comment above expand_vector_broadcast() states a precondition that the mode of op must be the element mode of vmode. But when expand_binop() called expand_vector_broadcast() to broadcast the shift amount, it only truncated the shift amount if it's too wide, but no action is performed if the shift amount is too narrow. Note that the assertion in expand_vector_broadcast is deliberately skipped in the backport, in order not to wake up latent "harmless" bugs. PR middle-end/124250 PR target/123807 gcc/ * optabs.cc (expand_binop): Extend the shift amount if it's narrower than the element of the shifted vector. gcc/testsuite/ * gcc.c-torture/compile/pr124250.c: New test. (cherry picked from commit 1139fdadc85a0b602a2833e6b7f2cfe2a8a90cdb) Diff: --- gcc/optabs.cc | 32 +++++++++++++++++--------- gcc/testsuite/gcc.c-torture/compile/pr124250.c | 8 +++++++ 2 files changed, 29 insertions(+), 11 deletions(-) diff --git a/gcc/optabs.cc b/gcc/optabs.cc index 84446f566d76..f9480ed9477a 100644 --- a/gcc/optabs.cc +++ b/gcc/optabs.cc @@ -421,9 +421,9 @@ force_expand_binop (machine_mode mode, optab binoptab, return true; } -/* Create a new vector value in VMODE with all elements set to OP. The - mode of OP must be the element mode of VMODE. If OP is a constant, - then the return value will be a constant. */ +/* Create a new vector value in VMODE with all elements set to OP. If OP + is not a constant, the mode of it must be the element mode of VMODE. + If OP is a constant, then the return value will be a constant. */ rtx expand_vector_broadcast (machine_mode vmode, rtx op) @@ -1622,15 +1622,25 @@ expand_binop (machine_mode mode, optab binoptab, rtx op0, rtx op1, if (otheroptab && (icode = optab_handler (otheroptab, mode)) != CODE_FOR_nothing) { - /* The scalar may have been extended to be too wide. Truncate - it back to the proper size to fit in the broadcast vector. */ + /* The scalar may be wider or narrower than the vector element. + Truncate or extend it to the proper size to fit in the + broadcast vector. */ scalar_mode inner_mode = GET_MODE_INNER (mode); - if (!CONST_INT_P (op1) - && (GET_MODE_BITSIZE (as_a <scalar_int_mode> (GET_MODE (op1))) - > GET_MODE_BITSIZE (inner_mode))) - op1 = force_reg (inner_mode, - simplify_gen_unary (TRUNCATE, inner_mode, op1, - GET_MODE (op1))); + if (!CONST_INT_P (op1)) + { + auto mode1 = as_a <scalar_int_mode> (GET_MODE (op1)); + int size1 = GET_MODE_BITSIZE (mode1); + int inner_size = GET_MODE_BITSIZE (inner_mode); + + if (size1 != inner_size) + { + auto unary = size1 > inner_size ? TRUNCATE : ZERO_EXTEND; + op1 = force_reg (inner_mode, + simplify_gen_unary (unary, inner_mode, + op1, mode1)); + } + } + rtx vop1 = expand_vector_broadcast (mode, op1); if (vop1) { diff --git a/gcc/testsuite/gcc.c-torture/compile/pr124250.c b/gcc/testsuite/gcc.c-torture/compile/pr124250.c new file mode 100644 index 000000000000..1435091dc0b8 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/compile/pr124250.c @@ -0,0 +1,8 @@ +typedef long long v2i64 __attribute__ ((vector_size (16), aligned (16))); +v2i64 a, b; + +void +test (int l) +{ + a = b >> (-l); +}
