diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 4564b0f77b..f15090aad9 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -1131,3 +1131,20 @@ _test: subl 4(%esp), %eax ret +//===---------------------------------------------------------------------===// + +For code like: +phi (undef, x) + +We get an implicit def on the undef side. If the phi is spilled, we then get: +implicitdef xmm1 +store xmm1 -> stack + +It should be possible to teach the x86 backend to "fold" the store into the +implicitdef, which just deletes the implicit def. + +These instructions should go away: +#IMPLICIT_DEF %xmm1 +movaps %xmm1, 192(%esp) +movaps %xmm1, 224(%esp) +movaps %xmm1, 176(%esp) |