diff options
Diffstat (limited to 'lib/Target/README.txt')
-rw-r--r-- | lib/Target/README.txt | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 4e14fbb..f85914b 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -254,6 +254,20 @@ unsigned long reverse(unsigned v) { //===---------------------------------------------------------------------===// +[LOOP DELETION] + +We don't delete this output free loop, because trip count analysis doesn't +realize that it is finite (if it were infinite, it would be undefined). Not +having this blocks Loop Idiom from matching strlen and friends. + +void foo(char *C) { + int x = 0; + while (*C) + ++x,++C; +} + +//===---------------------------------------------------------------------===// + [LOOP RECOGNITION] These idioms should be recognized as popcount (see PR1488): @@ -287,6 +301,16 @@ unsigned int popcount(unsigned int input) { return count; } +This should be recognized as CLZ: rdar://8459039 + +unsigned clz_a(unsigned a) { + int i; + for (i=0;i<32;i++) + if (a & (1<<(31-i))) + return i; + return 32; +} + This sort of thing should be added to the loop idiom pass. //===---------------------------------------------------------------------===// |