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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2020-11-25 23:01:48 +0100 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2020-11-27 22:19:41 +0100 |
| commit | cafabc769e77f14e47ab44866b304e51af42c44c (patch) | |
| tree | 4d8a3870d76d1ae0f0e304ecaab8cae22b180aac | |
| parent | 2b77484ed79f2d2edb032b5922236575e57dfb5c (diff) | |
| download | sparse-cafabc769e77f14e47ab44866b304e51af42c44c.tar.gz | |
convert SEL(x & BIT1, BIT2, 0) into SHIFT(x & BIT1, S)
Convert an expression like:
(x & (1 << A)) ? (1 << B) : 0
into:
(x & (1 << A)) << (B - A)
or:
(x & (1 << A)) >> (A - B)
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
| -rw-r--r-- | simplify.c | 15 | ||||
| -rw-r--r-- | validation/optim/select-and-shift.c | 1 |
2 files changed, 15 insertions, 1 deletions
@@ -2271,6 +2271,21 @@ static int simplify_select(struct instruction *insn) // both values must be non-zero return replace_with_pseudo(insn, src1); } + case OP_AND: + if (is_pow2(def->src2) && is_pow2(src1) && is_zero(src2) && insn->size == def->size && one_use(cond)) { + unsigned s1 = log2_exact(def->src2->value); + unsigned s2 = log2_exact(insn->src2->value); + unsigned shift; + + if (s1 == s2) + return replace_with_pseudo(insn, cond); + + // SEL(x & A, B, 0) --> SHIFT(x & A, S) + insn->opcode = (s1 < s2) ? OP_SHL : OP_LSR; + shift = (s1 < s2) ? (s2 - s1) : (s1 - s2); + insn->src2 = value_pseudo(shift); + return REPEAT_CSE; + } break; } diff --git a/validation/optim/select-and-shift.c b/validation/optim/select-and-shift.c index fbe044c7..5313fe4b 100644 --- a/validation/optim/select-and-shift.c +++ b/validation/optim/select-and-shift.c @@ -11,7 +11,6 @@ int bar(int p) { return ((p & B) ? A : 0) == ((((unsigned)p) & B) >> S); } /* * check-name: select-and-shift * check-command: test-linearize -Wno-decl $file - * check-known-to-fail * * check-output-ignore * check-output-returns: 1 |