From b5041b30851b1173170a8d281b2e9571a2a04bdd Mon Sep 17 00:00:00 2001 From: Nate Begeman Date: Wed, 13 Feb 2008 07:06:12 +0000 Subject: readme updates git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47051 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/PowerPC/README_ALTIVEC.txt | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'lib/Target/PowerPC/README_ALTIVEC.txt') diff --git a/lib/Target/PowerPC/README_ALTIVEC.txt b/lib/Target/PowerPC/README_ALTIVEC.txt index 143804da07..461b4123c7 100644 --- a/lib/Target/PowerPC/README_ALTIVEC.txt +++ b/lib/Target/PowerPC/README_ALTIVEC.txt @@ -177,3 +177,12 @@ which prevents the vnot pattern from matching. //===----------------------------------------------------------------------===// + +An alternative to the store/store/load approach for illegal insert element +lowering would be: + +1. store element to any ol' slot +2. lvx the slot +3. lvsl 0; splat index; vcmpeq to generate a select mask +4. lvsl slot + x; vperm to rotate result into correct slot +5. vsel result together. -- cgit v1.2.3