diff options
Diffstat (limited to 'gcc/loop-doloop.c')
| -rw-r--r-- | gcc/loop-doloop.c | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/gcc/loop-doloop.c b/gcc/loop-doloop.c index db6a014..02282d4 100644 --- a/gcc/loop-doloop.c +++ b/gcc/loop-doloop.c @@ -397,6 +397,42 @@ add_test (rtx cond, edge *e, basic_block dest) return true; } +/* Fold (add -1; zero_ext; add +1) operations to zero_ext if not wrapping. i.e: + + 73: r145:SI=r123:DI#0-0x1 + 74: r144:DI=zero_extend (r145:SI) + 75: r143:DI=r144:DI+0x1 + ... + 31: r135:CC=cmp (r123:DI,0) + 72: {pc={(r143:DI!=0x1)?L70:pc};r143:DI=r143:DI-0x1;...} + + r123:DI#0-0x1 is param count derived from loop->niter_expr equal to number of + loop iterations, if loop iterations expression doesn't overflow, then + (zero_extend (r123:DI#0-1))+1 can be simplified to zero_extend. */ + +static rtx +doloop_simplify_count (class loop *loop, scalar_int_mode mode, rtx count) +{ + widest_int iterations; + if (GET_CODE (count) == ZERO_EXTEND) + { + rtx extop0 = XEXP (count, 0); + if (GET_CODE (extop0) == PLUS) + { + rtx addop0 = XEXP (extop0, 0); + rtx addop1 = XEXP (extop0, 1); + + if (get_max_loop_iterations (loop, &iterations) + && wi::ltu_p (iterations, GET_MODE_MASK (GET_MODE (addop0))) + && addop1 == constm1_rtx) + return simplify_gen_unary (ZERO_EXTEND, mode, addop0, + GET_MODE (addop0)); + } + } + + return simplify_gen_binary (PLUS, mode, count, const1_rtx); +} + /* Modify the loop to use the low-overhead looping insn where LOOP describes the loop, DESC describes the number of iterations of the loop, and DOLOOP_INSN is the low-overhead looping insn to emit at the @@ -477,7 +513,7 @@ doloop_modify (class loop *loop, class niter_desc *desc, } if (increment_count) - count = simplify_gen_binary (PLUS, mode, count, const1_rtx); + count = doloop_simplify_count (loop, mode, count); /* Insert initialization of the count register into the loop header. */ start_sequence (); |