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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 | 952b5d19f0b1cbd752e3d6b854947f5205b6b313 (patch) | |
| tree | 450186dc0aa2d830f768b4e2d8b65fcb3b05fec8 /lib/Target/X86/README-SSE.txt | |
| parent | 7f526a841219bf99e0aee500e337144f2f3c2d63 (diff) | |
| download | external_llvm-952b5d19f0b1cbd752e3d6b854947f5205b6b313.zip external_llvm-952b5d19f0b1cbd752e3d6b854947f5205b6b313.tar.gz external_llvm-952b5d19f0b1cbd752e3d6b854947f5205b6b313.tar.bz2 | |
add a note
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41359 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/X86/README-SSE.txt')
| -rw-r--r-- | lib/Target/X86/README-SSE.txt | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt index 40404e5..cb857fb 100644 --- a/lib/Target/X86/README-SSE.txt +++ b/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. + +//===---------------------------------------------------------------------===// |