diff options
Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index bcc55b4..aad621f 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -1719,3 +1719,18 @@ static int foo(const char *X) { return strlen(X); } int bar() { return foo("abcd"); } //===---------------------------------------------------------------------===// + +InstCombine should use SimplifyDemandedBits to remove the or instruction: + +define i1 @test(i8 %x, i8 %y) { + %A = or i8 %x, 1 + %B = icmp ugt i8 %A, 3 + ret i1 %B +} + +Currently instcombine calls SimplifyDemandedBits with either all bits or just +the sign bit, if the comparison is obviously a sign test. In this case, we only +need all but the bottom two bits from %A, and if we gave that mask to SDB it +would delete the or instruction for us. + +//===---------------------------------------------------------------------===// |