sparse contains some code to simplify an AND masking followed by a truncating cast. However, this simplification is problematic because it doesn't keep the sizes consistent. For example, code like: and.32 %r3 <- %r2, $0x7fff trunc.16 %r4 <- (32) %r3 will be discarded with %r3 used in place of %r4. This is correct in the mathematical sense but %r4 had a size of 16 while %r3 has a size of 32, so using %r3 in place of %r4 will make the sizes inconsistent with unexpected consequences. We can more or less fix this by using another transformation that preserve the sizes: trunc.16 %r3 <- (32) %r2 and.16 %r4 <- %r3, $0x7fff which in itself doesn't optimize anything but: 1) the mask may be smaller 2) may trigger other simplification with the TRUNC or the AND. Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> --- simplify.c | 17 +++++++++++------ validation/optim/and-trunc.c | 1 - 2 files changed, 11 insertions(+), 7 deletions(-) diff --git a/simplify.c b/simplify.c index 0982d9d4b..336339fac 100644 --- a/simplify.c +++ b/simplify.c @@ -999,10 +999,18 @@ static int simplify_cast(struct instruction *insn) /* A cast of a AND might be a no-op.. */ switch (insn->opcode) { case OP_TRUNC: + if (nbr_users(src) > 1) + break; + def->opcode = OP_TRUNC; + def->orig_type = def->type; + def->type = insn->type; + def->size = size; + + insn->opcode = OP_AND; mask = val->value; - if (!(mask >> (size-1))) - goto simplify; - break; + mask &= (1ULL << size) - 1; + insn->src2 = value_pseudo(mask); + return REPEAT_CSE; } break; case OP_TRUNC: @@ -1029,9 +1037,6 @@ static int simplify_cast(struct instruction *insn) } return 0; - -simplify: - return replace_with_pseudo(insn, src); } static int simplify_select(struct instruction *insn) diff --git a/validation/optim/and-trunc.c b/validation/optim/and-trunc.c index bcb80bbe0..df1e4d03e 100644 --- a/validation/optim/and-trunc.c +++ b/validation/optim/and-trunc.c @@ -11,7 +11,6 @@ short umask(unsigned short x) /* * check-name: and-trunc * check-command: test-linearize -Wno-decl $file - * check-known-to-fail * * check-output-ignore * check-output-excludes: sext\\. -- 2.18.0 -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html