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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46405 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-01-26 20:12:07 +00:00
parent ba96fbc164
commit 4d53049c92
1 changed files with 18 additions and 0 deletions
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18
lib/Target/X86/README-SSE.txt
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@ -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.
//===---------------------------------------------------------------------===//