* hist.h (struct histogram)

	(histograms, num_histograms): New.
	* hist.c (find_histogram, find_histogram_for_pc)
	(read_histogram_header): New.
	(s_lowpc, s_highpc, lowpc, highpc, hist_num_bins)
	(hist_sample): Remove.
	(hist_read_rec): Use the above, and handle multiple
	histogram records with disjoint address ranges.
	(hist_write_hist): Support several histogram records.
	(scale_and_align_entries): Adjust for multiple histograms.
	(hist_assign_samples_1): New.
	(hist_assign_samples): Use the above.
	(hist_clip_symbol_address): New.
	* hist.h (hist_check_address)
	(hist_clip_symbol_address): Declare.
	* gmon_io.c (gmon_out_read, gmon_out_write): Adjust handling
	of legacy format for multiple histogram changes.
	* corefile.c (find_call): Check for core_text_space and
	clip symbol address range here.
	* vax.c	(vax_find_call): Don't check for
	core_text_space, or clip the symbol's address range here.
	Use hist_check_address to check call's target address.
	* sparc.c: Likewise.
	* tahoe.c: Likewise.
	* i386.c: Likewise.
	* mips.c: Likewise. Also use core_text_sect->vma as the base
	address for code accesses, just like other machine-specific
	routines do.
	* gprof.texi: Adjust for the new logic.

1 files changed, 6 insertions, 5 deletions

diff --git a/gprof/gprof.texi b/gprof/gprof.texi
index f8be278..969d60e 100644
--- a/gprof/gprof.texi
+++ b/gprof/gprof.texi
@@ -2082,11 +2082,12 @@ New-style histogram records are read by @code{hist.c:@-hist_read_rec}.
 For the first histogram record, allocate a memory array to hold
 all the bins, and read them in.
 When multiple profile data files (or files with multiple histogram
-records) are read, the starting address, ending address, number
-of bins and sampling rate must match between the various histograms,
-or a fatal error will result.
-If everything matches, just sum the additional histograms into
-the existing in-memory array.
+records) are read, the memory ranges of each pair of histogram records
+must be either equal, or non-overlapping.  For each pair of histogram
+records, the resolution (memory region size divided by the number of
+bins) must be the same.  The time unit must be the same for all 
+histogram records. If the above containts are met, all histograms
+for the same memory range are merged.
 
 As each call graph record is read (@code{call_graph.c:@-cg_read_rec}),
 the parent and child addresses