diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Target/X86/README-SSE.txt | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt index cadfc20..fe6fa85 100644 --- a/lib/Target/X86/README-SSE.txt +++ b/lib/Target/X86/README-SSE.txt @@ -704,3 +704,21 @@ This currently compiles to: We should use movmskp{s|d} instead. +//===---------------------------------------------------------------------===// + +CodeGen/X86/vec_align.ll tests whether we can turn 4 scalar loads into a single +(aligned) vector load. This functionality has a couple of problems. + +1. The code to infer alignment from loads of globals is in the X86 backend, + not the dag combiner. This is because dagcombine2 needs to be able to see + through the X86ISD::Wrapper node, which DAGCombine can't really do. +2. The code for turning 4 x load into a single vector load is target + independent and should be moved to the dag combiner. +3. The code for turning 4 x load into a vector load can only handle a direct + load from a global or a direct load from the stack. It should be generalized + to handle any load from P, P+4, P+8, P+12, where P can be anything. +4. The alignment inference code cannot handle loads from globals in non-static + mode because it doesn't look through the extra dyld stub load. If you try + vec_align.ll without -relocation-model=static, you'll see what I mean. + +//===---------------------------------------------------------------------===// |