6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-08-09 11:25:55 +00:00
Code Issues Projects Releases Wiki Activity

some more PRE/GVN/DSE related notes.

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60633 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2008-12-06 22:52:12 +00:00
parent f96ca79cf3
commit 6a09a74e46
1 changed files with 51 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
lib/Target/README.txt
View File

@@ -1307,6 +1307,9 @@ bb2: ; preds = %bb, %bb1
DSE should sink partially dead stores to get the store out of the loop. DSE should sink partially dead stores to get the store out of the loop.
Here's another partial dead case:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12395
//===---------------------------------------------------------------------===// //===---------------------------------------------------------------------===//
Scalar PRE hoists the mul in the common block up to the else: Scalar PRE hoists the mul in the common block up to the else:
@@ -1367,6 +1370,54 @@ bb3: ; preds = %bb1, %bb2, %bb
%11 is fully redundant, an in BB2 it should have the value %8. %11 is fully redundant, an in BB2 it should have the value %8.
GCC PR33344 is a similar case.
//===---------------------------------------------------------------------===// //===---------------------------------------------------------------------===//
There are many load PRE testcases in testsuite/gcc.dg/tree-ssa/loadpre* in the
GCC testsuite. There are many pre testcases as ssa-pre-*.c
Other simple load PRE cases:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35287
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34677 (licm does this)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29789 (SPEC2K6)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23455
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14705
//===---------------------------------------------------------------------===//
When GVN/PRE finds a store of float* to a must aliases pointer when expecting
an int*, it should turn it into a bitcast. This is a nice generalization of
the SROA hack that would apply to other cases.
One example (that requires crazy phi translation) is:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16799
//===---------------------------------------------------------------------===//
A/B get pinned to the stack because we turn an if/then into a select instead
of PRE'ing the load/store. This may be fixable in instcombine:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37892
Interesting missed case because of control flow flattening (should be 2 loads):
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26629
//===---------------------------------------------------------------------===//
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19633
We could eliminate the branch condition here, loading from null is undefined:
struct S { int w, x, y, z; };
struct T { int r; struct S s; };
void bar (struct S, int);
void foo (int a, struct T b)
{
struct S *c = 0;
if (a)
c = &b.s;
bar (*c, a);
}
//===---------------------------------------------------------------------===//