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author | Richard Sandiford <rdsandiford@googlemail.com> | 2010-07-12 19:03:25 +0000 |
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committer | Richard Sandiford <rsandifo@gcc.gnu.org> | 2010-07-12 19:03:25 +0000 |
commit | c371bb73807c48f1a708c51f113caea45f0347b1 (patch) | |
tree | fa440aa1ca8e5ec6721496213be7f7cdaa25daa9 /gcc/expmed.h | |
parent | aa1c5d72e9cb30ddea2f930b6f94045dd8f2dcbc (diff) | |
download | gcc-c371bb73807c48f1a708c51f113caea45f0347b1.zip gcc-c371bb73807c48f1a708c51f113caea45f0347b1.tar.gz gcc-c371bb73807c48f1a708c51f113caea45f0347b1.tar.bz2 |
gcc/
* expmed.h (alg_code, mult_cost, MULT_COST_LESS, CHEAPER_MULT_COST)
(algorithm, alg_hash_entry, NUM_ALG_HASH_ENTRIES, alg_hash): Moved
from expmed.c.
(target_expmed): Add x_alg_hash and x_alg_hash_used_p.
(alg_hash, alg_hash_used_p): New macros.
* expmed.c (init_expmed): Clear alg_hash if reinitializing.
(alg_code, mult_cost, MULT_COST_LESS, CHEAPER_MULT_COST, algorithm)
(alg_hash_entry, NUM_ALG_HASH_ENTRIES, alg_hash): Moved to expmed.h.
From-SVN: r162104
Diffstat (limited to 'gcc/expmed.h')
-rw-r--r-- | gcc/expmed.h | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/gcc/expmed.h b/gcc/expmed.h index fcf16dc..37f5755 100644 --- a/gcc/expmed.h +++ b/gcc/expmed.h @@ -22,8 +22,118 @@ along with GCC; see the file COPYING3. If not see #ifndef EXPMED_H #define EXPMED_H 1 +enum alg_code { + alg_unknown, + alg_zero, + alg_m, alg_shift, + alg_add_t_m2, + alg_sub_t_m2, + alg_add_factor, + alg_sub_factor, + alg_add_t2_m, + alg_sub_t2_m, + alg_impossible +}; + +/* This structure holds the "cost" of a multiply sequence. The + "cost" field holds the total rtx_cost of every operator in the + synthetic multiplication sequence, hence cost(a op b) is defined + as rtx_cost(op) + cost(a) + cost(b), where cost(leaf) is zero. + The "latency" field holds the minimum possible latency of the + synthetic multiply, on a hypothetical infinitely parallel CPU. + This is the critical path, or the maximum height, of the expression + tree which is the sum of rtx_costs on the most expensive path from + any leaf to the root. Hence latency(a op b) is defined as zero for + leaves and rtx_cost(op) + max(latency(a), latency(b)) otherwise. */ + +struct mult_cost { + short cost; /* Total rtx_cost of the multiplication sequence. */ + short latency; /* The latency of the multiplication sequence. */ +}; + +/* This macro is used to compare a pointer to a mult_cost against an + single integer "rtx_cost" value. This is equivalent to the macro + CHEAPER_MULT_COST(X,Z) where Z = {Y,Y}. */ +#define MULT_COST_LESS(X,Y) ((X)->cost < (Y) \ + || ((X)->cost == (Y) && (X)->latency < (Y))) + +/* This macro is used to compare two pointers to mult_costs against + each other. The macro returns true if X is cheaper than Y. + Currently, the cheaper of two mult_costs is the one with the + lower "cost". If "cost"s are tied, the lower latency is cheaper. */ +#define CHEAPER_MULT_COST(X,Y) ((X)->cost < (Y)->cost \ + || ((X)->cost == (Y)->cost \ + && (X)->latency < (Y)->latency)) + +/* This structure records a sequence of operations. + `ops' is the number of operations recorded. + `cost' is their total cost. + The operations are stored in `op' and the corresponding + logarithms of the integer coefficients in `log'. + + These are the operations: + alg_zero total := 0; + alg_m total := multiplicand; + alg_shift total := total * coeff + alg_add_t_m2 total := total + multiplicand * coeff; + alg_sub_t_m2 total := total - multiplicand * coeff; + alg_add_factor total := total * coeff + total; + alg_sub_factor total := total * coeff - total; + alg_add_t2_m total := total * coeff + multiplicand; + alg_sub_t2_m total := total * coeff - multiplicand; + + The first operand must be either alg_zero or alg_m. */ + +struct algorithm +{ + struct mult_cost cost; + short ops; + /* The size of the OP and LOG fields are not directly related to the + word size, but the worst-case algorithms will be if we have few + consecutive ones or zeros, i.e., a multiplicand like 10101010101... + In that case we will generate shift-by-2, add, shift-by-2, add,..., + in total wordsize operations. */ + enum alg_code op[MAX_BITS_PER_WORD]; + char log[MAX_BITS_PER_WORD]; +}; + +/* The entry for our multiplication cache/hash table. */ +struct alg_hash_entry { + /* The number we are multiplying by. */ + unsigned HOST_WIDE_INT t; + + /* The mode in which we are multiplying something by T. */ + enum machine_mode mode; + + /* The best multiplication algorithm for t. */ + enum alg_code alg; + + /* The cost of multiplication if ALG_CODE is not alg_impossible. + Otherwise, the cost within which multiplication by T is + impossible. */ + struct mult_cost cost; + + /* Optimized for speed? */ + bool speed; +}; + +/* The number of cache/hash entries. */ +#if HOST_BITS_PER_WIDE_INT == 64 +#define NUM_ALG_HASH_ENTRIES 1031 +#else +#define NUM_ALG_HASH_ENTRIES 307 +#endif + /* Target-dependent globals. */ struct target_expmed { + /* Each entry of ALG_HASH caches alg_code for some integer. This is + actually a hash table. If we have a collision, that the older + entry is kicked out. */ + struct alg_hash_entry x_alg_hash[NUM_ALG_HASH_ENTRIES]; + + /* True if x_alg_hash might already have been used. */ + bool x_alg_hash_used_p; + /* Nonzero means divides or modulus operations are relatively cheap for powers of two, so don't use branches; emit the operation instead. Usually, this will mean that the MD file will emit non-branch @@ -54,6 +164,10 @@ extern struct target_expmed *this_target_expmed; #define this_target_expmed (&default_target_expmed) #endif +#define alg_hash \ + (this_target_expmed->x_alg_hash) +#define alg_hash_used_p \ + (this_target_expmed->x_alg_hash_used_p) #define sdiv_pow2_cheap \ (this_target_expmed->x_sdiv_pow2_cheap) #define smod_pow2_cheap \ |