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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-08-18 18:42:17 +0200 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-08-22 09:26:18 +0200 |
| commit | cb4bed63e19e64d62364337cca20285f782ac6fd (patch) | |
| tree | b78904af07a4813721c4e259fcaf67e2f2e03d3b | |
| parent | 729be196bb860270de32ec076873c6d327f592a0 (diff) | |
| download | sparse-dev-cb4bed63e19e64d62364337cca20285f782ac6fd.tar.gz | |
simplify ((x & M) << S) when (M << S) == 0
The instructions SHL(AND(x, M), S) can be simplified to 0
if (M << S) == 0.
For example code like:
unsigned foo(unsigned x)
{
return (x & 0xfff00000) << 12;
}
is now simplified into:
foo:
ret.32 $0
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
| -rw-r--r-- | simplify.c | 11 | ||||
| -rw-r--r-- | validation/optim/shl-and0.c | 1 |
2 files changed, 11 insertions, 1 deletions
@@ -720,6 +720,17 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v if (value >= size) goto zero; switch(DEF_OPCODE(def, pseudo)) { + case OP_AND: + // simplify (A & M) << S + if (!constant(def->src2)) + break; + mask = bits_mask(insn->size) >> value; + omask = def->src2->value; + nmask = omask & mask; + if (nmask == 0) + return replace_with_pseudo(insn, value_pseudo(0)); + // do not simplify into ((A << S) & (M << S)) + break; case OP_LSR: // replace ((x >> S) << S) // by (x & (-1 << S)) diff --git a/validation/optim/shl-and0.c b/validation/optim/shl-and0.c index 289859ae..894bd882 100644 --- a/validation/optim/shl-and0.c +++ b/validation/optim/shl-and0.c @@ -7,7 +7,6 @@ unsigned shl_and0(unsigned x) /* * check-name: shl-and0 * check-command: test-linearize -Wno-decl $file - * check-known-to-fail * * check-output-ignore * check-output-contains: ret\\..*\\$0$ |