llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-10 18:34:09 +00:00

History

Evan Cheng 02c4285643 Fixes a nasty dag combiner bug that causes a bunch of tests to fail at -O0.

It's not safe to use the two value CombineTo variant to combine away a dead load.
e.g. 
v1, chain2 = load chain1, loc
v2, chain3 = load chain2, loc
v3         = add v2, c 
Now we replace use of v1 with undef, use of chain2 with chain1.
ReplaceAllUsesWith() will iterate through uses of the first load and update operands:
v1, chain2 = load chain1, loc
v2, chain3 = load chain1, loc
v3         = add v2, c 
Now the second load is the same as the first load, SelectionDAG cse will ensure
the use of second load is replaced with the first load.
v1, chain2 = load chain1, loc
v3         = add v1, c
Then v1 is replaced with undef and bad things happen.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46099 91177308-0d34-0410-b5e6-96231b3b80d8

2008-01-16 23:11:54 +00:00

Analysis

Accept both %y, %x and %x, %y as valid answers.

2008-01-06 03:12:44 +00:00