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-rw-r--r--gcc/ChangeLog7
-rw-r--r--gcc/config/i386/driver-i386.c136
-rw-r--r--gcc/testsuite/ChangeLog4
-rw-r--r--gcc/testsuite/gcc.dg/tree-ssa/prefetch-4.c18
-rw-r--r--gcc/tree-ssa-loop-prefetch.c45
5 files changed, 192 insertions, 18 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b0e26a9..9c75bc2 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2007-03-01 Zdenek Dvorak <dvorakz@suse.cz>
+
+ * tree-ssa-loop-prefetch.c (determine_unroll_factor): Bound the unroll
+ factor by the estimated number of iterations.
+ (loop_prefetch_arrays): Do not prefetch in loops that iterate less than
+ prefetch latency.
+
2007-03-01 Richard Henderson <rth@redhat.com>
* expr.c (emit_move_complex_push): Export.
diff --git a/gcc/config/i386/driver-i386.c b/gcc/config/i386/driver-i386.c
index df43512..3a5d29d 100644
--- a/gcc/config/i386/driver-i386.c
+++ b/gcc/config/i386/driver-i386.c
@@ -47,6 +47,131 @@ const char *host_detect_local_cpu (int argc, const char **argv);
#define bit_3DNOWP (1 << 30)
#define bit_LM (1 << 29)
+/* Returns parameters that describe L1_ASSOC associative cache of size
+ L1_SIZEKB with lines of size L1_LINE. */
+
+static char *
+describe_cache (unsigned l1_sizekb, unsigned l1_line,
+ unsigned l1_assoc ATTRIBUTE_UNUSED)
+{
+ char size[1000], line[1000];
+ unsigned size_in_lines;
+
+ /* At the moment, gcc middle-end does not use the information about the
+ associativity of the cache. */
+
+ size_in_lines = (l1_sizekb * 1024) / l1_line;
+
+ sprintf (size, "--param l1-cache-size=%u", size_in_lines);
+ sprintf (line, "--param l1-cache-line-size=%u", l1_line);
+
+ return concat (size, " ", line, " ", NULL);
+}
+
+/* Returns the description of caches for an AMD processor. */
+
+static char *
+detect_caches_amd (unsigned max_ext_level)
+{
+ unsigned eax, ebx, ecx, edx;
+ unsigned l1_sizekb, l1_line, l1_assoc;
+
+ if (max_ext_level < 0x80000005)
+ return NULL;
+
+ cpuid (0x80000005, eax, ebx, ecx, edx);
+
+ l1_line = ecx & 0xff;
+ l1_sizekb = (ecx >> 24) & 0xff;
+ l1_assoc = (ecx >> 16) & 0xff;
+
+ return describe_cache (l1_sizekb, l1_line, l1_assoc);
+}
+
+/* Stores the size of the L1 cache and cache line, and the associativity
+ of the cache according to REG to L1_SIZEKB, L1_LINE and L1_ASSOC. */
+
+static void
+decode_caches_intel (unsigned reg, unsigned *l1_sizekb, unsigned *l1_line,
+ unsigned *l1_assoc)
+{
+ unsigned i, val;
+
+ if (((reg >> 31) & 1) != 0)
+ return;
+
+ for (i = 0; i < 4; i++)
+ {
+ val = reg & 0xff;
+ reg >>= 8;
+
+ switch (val)
+ {
+ case 0xa:
+ *l1_sizekb = 8;
+ *l1_line = 32;
+ *l1_assoc = 2;
+ break;
+ case 0xc:
+ *l1_sizekb = 16;
+ *l1_line = 32;
+ *l1_assoc = 4;
+ break;
+ case 0x2c:
+ *l1_sizekb = 32;
+ *l1_line = 64;
+ *l1_assoc = 8;
+ break;
+ case 0x60:
+ *l1_sizekb = 16;
+ *l1_line = 64;
+ *l1_assoc = 8;
+ break;
+ case 0x66:
+ *l1_sizekb = 8;
+ *l1_line = 64;
+ *l1_assoc = 4;
+ break;
+ case 0x67:
+ *l1_sizekb = 16;
+ *l1_line = 64;
+ *l1_assoc = 4;
+ break;
+ case 0x68:
+ *l1_sizekb = 32;
+ *l1_line = 64;
+ *l1_assoc = 4;
+ break;
+
+ default:
+ break;
+ }
+ }
+}
+
+/* Returns the description of caches for an intel processor. */
+
+static char *
+detect_caches_intel (unsigned max_level)
+{
+ unsigned eax, ebx, ecx, edx;
+ unsigned l1_sizekb = 0, l1_line = 0, assoc = 0;
+
+ if (max_level < 2)
+ return NULL;
+
+ cpuid (2, eax, ebx, ecx, edx);
+
+ decode_caches_intel (eax, &l1_sizekb, &l1_line, &assoc);
+ decode_caches_intel (ebx, &l1_sizekb, &l1_line, &assoc);
+ decode_caches_intel (ecx, &l1_sizekb, &l1_line, &assoc);
+ decode_caches_intel (edx, &l1_sizekb, &l1_line, &assoc);
+ if (!l1_sizekb)
+ return (char *) "";
+
+ return describe_cache (l1_sizekb, l1_line, assoc);
+}
+
/* This will be called by the spec parser in gcc.c when it sees
a %:local_cpu_detect(args) construct. Currently it will be called
with either "arch" or "tune" as argument depending on if -march=native
@@ -62,6 +187,7 @@ const char *host_detect_local_cpu (int argc, const char **argv);
const char *host_detect_local_cpu (int argc, const char **argv)
{
const char *cpu = NULL;
+ const char *cache = "";
enum processor_type processor = PROCESSOR_I386;
unsigned int eax, ebx, ecx, edx;
unsigned int max_level;
@@ -126,6 +252,14 @@ const char *host_detect_local_cpu (int argc, const char **argv)
is_amd = vendor == *(unsigned int*)"Auth";
+ if (!arch)
+ {
+ if (is_amd)
+ cache = detect_caches_amd (ext_level);
+ else if (vendor == *(unsigned int*)"Genu")
+ cache = detect_caches_intel (max_level);
+ }
+
if (is_amd)
{
if (has_mmx)
@@ -283,7 +417,7 @@ const char *host_detect_local_cpu (int argc, const char **argv)
}
done:
- return concat ("-m", argv[0], "=", cpu, NULL);
+ return concat (cache, "-m", argv[0], "=", cpu, NULL);
}
#else
/* If we aren't compiling with GCC we just provide a minimal
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 1f432cf..e2cf6d9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2007-03-01 Zdenek Dvorak <dvorakz@suse.cz>
+
+ * gcc.dg/tree-ssa/prefetch-4.c: New test.
+
2007-03-01 Simon Baldwin <simonb@google.com>
PR c++/23689
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/prefetch-4.c b/gcc/testsuite/gcc.dg/tree-ssa/prefetch-4.c
new file mode 100644
index 0000000..8a5230e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/prefetch-4.c
@@ -0,0 +1,18 @@
+/* The loop rolls too little, hence the prefetching would not be useful. */
+
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-require-effective-target ilp32 } */
+/* { dg-options "-O2 -fprefetch-loop-arrays -march=athlon -fdump-tree-final_cleanup" } */
+
+int xxx[20];
+
+void foo (int n)
+{
+ int i;
+
+ for (i = 0; i < n; i++)
+ xxx[i] = i;
+}
+
+/* { dg-final { scan-tree-dump-times "prefetch" 0 "final_cleanup" } } */
+/* { dg-final { cleanup-tree-dump "final_cleanup" } } */
diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c
index e0612b9..53977d8 100644
--- a/gcc/tree-ssa-loop-prefetch.c
+++ b/gcc/tree-ssa-loop-prefetch.c
@@ -885,13 +885,14 @@ should_unroll_loop_p (struct loop *loop, struct tree_niter_desc *desc,
/* Determine the coefficient by that unroll LOOP, from the information
contained in the list of memory references REFS. Description of
- umber of iterations of LOOP is stored to DESC. AHEAD is the number
- of iterations ahead that we need to prefetch. NINSNS is number of
- insns of the LOOP. */
+ umber of iterations of LOOP is stored to DESC. NINSNS is the number of
+ insns of the LOOP. EST_NITER is the estimated number of iterations of
+ the loop, or -1 if no estimate is available. */
static unsigned
determine_unroll_factor (struct loop *loop, struct mem_ref_group *refs,
- unsigned ninsns, struct tree_niter_desc *desc)
+ unsigned ninsns, struct tree_niter_desc *desc,
+ HOST_WIDE_INT est_niter)
{
unsigned upper_bound;
unsigned nfactor, factor, mod_constraint;
@@ -906,6 +907,12 @@ determine_unroll_factor (struct loop *loop, struct mem_ref_group *refs,
gains from better scheduling and decreasing loop overhead, which is not
the case here. */
upper_bound = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / ninsns;
+
+ /* If we unrolled the loop more times than it iterates, the unrolled version
+ of the loop would be never entered. */
+ if (est_niter >= 0 && est_niter < (HOST_WIDE_INT) upper_bound)
+ upper_bound = est_niter;
+
if (upper_bound <= 1)
return 1;
@@ -935,7 +942,8 @@ static bool
loop_prefetch_arrays (struct loop *loop)
{
struct mem_ref_group *refs;
- unsigned ahead, ninsns, unroll_factor;
+ unsigned ahead, ninsns, time, unroll_factor;
+ HOST_WIDE_INT est_niter;
struct tree_niter_desc desc;
bool unrolled = false;
@@ -950,21 +958,24 @@ loop_prefetch_arrays (struct loop *loop)
/* Step 3: determine the ahead and unroll factor. */
- /* FIXME: We should use not size of the loop, but the average number of
- instructions executed per iteration of the loop. */
- ninsns = tree_num_loop_insns (loop, &eni_time_weights);
- ahead = (PREFETCH_LATENCY + ninsns - 1) / ninsns;
- unroll_factor = determine_unroll_factor (loop, refs, ninsns, &desc);
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "Ahead %d, unroll factor %d\n", ahead, unroll_factor);
+ /* FIXME: the time should be weighted by the probabilities of the blocks in
+ the loop body. */
+ time = tree_num_loop_insns (loop, &eni_time_weights);
+ ahead = (PREFETCH_LATENCY + time - 1) / time;
+ est_niter = estimated_loop_iterations_int (loop, false);
- /* If the loop rolls less than the required unroll factor, prefetching
- is useless. */
- if (unroll_factor > 1
- && cst_and_fits_in_hwi (desc.niter)
- && (unsigned HOST_WIDE_INT) int_cst_value (desc.niter) < unroll_factor)
+ /* The prefetches will run for AHEAD iterations of the original loop. Unless
+ the loop rolls at least AHEAD times, prefetching the references does not
+ make sense. */
+ if (est_niter >= 0 && est_niter <= (HOST_WIDE_INT) ahead)
goto fail;
+ ninsns = tree_num_loop_insns (loop, &eni_size_weights);
+ unroll_factor = determine_unroll_factor (loop, refs, ninsns, &desc,
+ est_niter);
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Ahead %d, unroll factor %d\n", ahead, unroll_factor);
+
/* Step 4: what to prefetch? */
if (!schedule_prefetches (refs, unroll_factor, ahead))
goto fail;
generated by cgit v1.1 at 2025-06-01 08:04:55 +0000