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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-07-23 22:27:56 +0200 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2018-07-25 16:36:52 +0200 |
| commit | eb180d9c0f5838c6b47c63ec475f3088c775cfd3 (patch) | |
| tree | c8582eb82b1e15187530672ecd49beb006b4e684 | |
| parent | e703906715b38a515c8d0a4815ee8e357ff1f6ba (diff) | |
| download | sparse-dev-eb180d9c0f5838c6b47c63ec475f3088c775cfd3.tar.gz | |
shift: simplify ASR(LSR(x,N),N')
Since an LSR with an in-range shift count will insert a zero in
the MSB, a subsequent ASR will be equivalent to an LSR of the same
count or equivalently, the combinaison the these two shifts is
equivalent to a single LSR with a shift count equal to the sum
of the two initial counts.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
| -rw-r--r-- | simplify.c | 5 | ||||
| -rw-r--r-- | validation/optim/lsr-asr.c | 42 |
2 files changed, 46 insertions, 1 deletions
@@ -590,6 +590,7 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v break; def = pseudo->def; switch (def->opcode) { + case OP_LSR: case OP_ASR: if (def == insn) // cyclic DAG! break; @@ -600,7 +601,9 @@ static int simplify_shift(struct instruction *insn, pseudo_t pseudo, long long v if (nval > insn->size) break; value += nval; - if (value >= size) + if (def->opcode == OP_LSR) + insn->opcode = OP_LSR; + else if (value >= size) value = size - 1; goto new_value; } diff --git a/validation/optim/lsr-asr.c b/validation/optim/lsr-asr.c new file mode 100644 index 00000000..aee46940 --- /dev/null +++ b/validation/optim/lsr-asr.c @@ -0,0 +1,42 @@ +int lsrasr0(unsigned int x) +{ + return ((int) (x >> 15)) >> 15; +} + +int lsrasr1(unsigned int x) +{ + return ((int) (x >> 16)) >> 15; +} + +int lsrasr2(unsigned int x) +{ + return ((int) (x >> 16)) >> 16; +} + +/* + * check-name: lsr-asr + * check-command: test-linearize -Wno-decl $file + * + * check-output-start +lsrasr0: +.L0: + <entry-point> + lsr.32 %r3 <- %arg1, $30 + ret.32 %r3 + + +lsrasr1: +.L2: + <entry-point> + lsr.32 %r7 <- %arg1, $31 + ret.32 %r7 + + +lsrasr2: +.L4: + <entry-point> + ret.32 $0 + + + * check-output-end + */ |