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| author | Chris Lattner <sabre@nondot.org> | 2007-08-24 15:17:59 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2007-08-24 15:17:59 +0000 |
| commit | 51883acec1c10f92e808f4cd6c472caef15bd200 (patch) | |
| tree | 565cce9c017991531c902e0c432cf8cfdf166d15 /llvm | |
| parent | 4bc9298f2a6ad6fbf6823cb706cdcd8cb41cdd21 (diff) | |
| download | bcm5719-llvm-51883acec1c10f92e808f4cd6c472caef15bd200.tar.gz bcm5719-llvm-51883acec1c10f92e808f4cd6c472caef15bd200.zip | |
add a note
llvm-svn: 41359
Diffstat (limited to 'llvm')
| -rw-r--r-- | llvm/lib/Target/X86/README-SSE.txt | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/README-SSE.txt b/llvm/lib/Target/X86/README-SSE.txt index 40404e53e8b..cb857fbf59f 100644 --- a/llvm/lib/Target/X86/README-SSE.txt +++ b/llvm/lib/Target/X86/README-SSE.txt @@ -630,3 +630,17 @@ _bar: ret //===---------------------------------------------------------------------===// + +We should materialize vecetor constants like "all ones" and "signbit" with +code like: + + cmpeqps xmm1, xmm1 ; xmm1 = all-ones + +and: + cmpeqps xmm1, xmm1 ; xmm1 = all-ones + psrlq xmm1, 31 ; xmm1 = all 100000000000... + +instead of using a load from the constant pool. The later is important for +ABS/NEG/copysign etc. + +//===---------------------------------------------------------------------===// |
