target: Correct profiling calculation

1. high_pc should be (maximum sample + 1) (Refer to gprof source code)
2. bucket index should be

     sample offset
    --------------- x (number of bucket)
	 sample range

For example, if minimum sample is 0 and maximum sample is 5
and the number of bucket is 3.

a = sampled_address - 0
b = 3
c = 6
(a, b, c refer to source code variables)

sampled_address = 0, => a = 0, => bucket_index = 0
sampled_address = 1, => a = 1, => bucket_index = 0
sampled_address = 2, => a = 2, => bucket_index = 1
sampled_address = 3, => a = 3, => bucket_index = 1
sampled_address = 4, => a = 4, => bucket_index = 2
sampled_address = 5, => a = 5, => bucket_index = 2

Change-Id: Ia9fa0e4d9c7183e3e9d7ceaf73e63729f07aa2ce
Signed-off-by: Hsiangkai Wang <hsiangkai@gmail.com>
Reviewed-on: http://openocd.zylin.com/1607
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/target/target.c b/src/target/target.c
index 11b12e5e..1ea1a616 100644
--- a/src/target/target.c
+++ b/src/target/target.c
@@ -3387,7 +3387,11 @@ static void writeGmon(uint32_t *samples, uint32_t sampleNum, const char *filenam
 			max = samples[i];
 	}
 
-	int addressSpace = (max - min + 1);
+	/* max should be (largest sample + 1)
+	 * Refer to binutils/gprof/hist.c (find_histogram_for_pc) */
+	max++;
+
+	int addressSpace = max - min;
 	assert(addressSpace >= 2);
 
 	static const uint32_t maxBuckets = 16 * 1024; /* maximum buckets. */
@@ -3403,8 +3407,8 @@ static void writeGmon(uint32_t *samples, uint32_t sampleNum, const char *filenam
 	for (i = 0; i < sampleNum; i++) {
 		uint32_t address = samples[i];
 		long long a = address - min;
-		long long b = numBuckets - 1;
-		long long c = addressSpace - 1;
+		long long b = numBuckets;
+		long long c = addressSpace;
 		int index_t = (a * b) / c; /* danger!!!! int32 overflows */
 		buckets[index_t]++;
 	}