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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2016-12-11 22:13:28 +0100 |
|---|---|---|
| committer | Christopher Li <sparse@chrisli.org> | 2017-02-13 09:34:46 +0800 |
| commit | e460239ea1bc22517e1e62dabd24e9e9ddb66c15 (patch) | |
| tree | 7613ec2f419acbc78ec742076d1d8bcb2cc136e7 | |
| parent | e5f70312b25b77a57a2ca16acb94d726af15f5f9 (diff) | |
| download | sparse-dev-e460239ea1bc22517e1e62dabd24e9e9ddb66c15.tar.gz | |
simplify '(x || x)' and '(x && x)'
The operators '||' and '&&' being idempotent, the expressions
'(x || x)' and '(x && x)' can be simplified to a test against zero.
Note: they could even be replaced by 'x' itself but only if 'x' is
already a boolean expression/has already been tested against zero.
If it is the case, the redundant test this will be optimized away
in further steps.
For example, test-linearize on the following code:
int ior(int a) { return a || a; }
emitted the following instructions:
or-bool.32 %r3 <- %arg1, %arg1
after the patch, it now emits:
setne.32 %r3 <- %arg1, $0
which is easier to combine with others simplifications.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Christopher Li <sparse@chrisli.org>
| -rw-r--r-- | simplify.c | 8 | ||||
| -rw-r--r-- | validation/optim/bool-same-args.c | 12 |
2 files changed, 16 insertions, 4 deletions
@@ -646,10 +646,10 @@ static int simplify_binop_same_args(struct instruction *insn, pseudo_t arg) case OP_AND_BOOL: case OP_OR_BOOL: - // simplification is correct only if the operands - // have already been compared against zero which - // is not enforced. - break; + remove_usage(arg, &insn->src2); + insn->src2 = value_pseudo(0); + insn->opcode = OP_SET_NE; + return REPEAT_CSE; default: break; diff --git a/validation/optim/bool-same-args.c b/validation/optim/bool-same-args.c new file mode 100644 index 00000000..0ae4684e --- /dev/null +++ b/validation/optim/bool-same-args.c @@ -0,0 +1,12 @@ +static int ior(int a) { return a || a; } +static int and(int a) { return a && a; } + +/* + * check-name: bool-same-args + * check-command: test-linearize $file + * check-output-ignore + * + * check-output-excludes: or-bool\\. + * check-output-excludes: and-bool\\. + * check-output-contains: setne\\. + */ |