move some stuff around, clean things up

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27802 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/README_ALTIVEC.txt b/lib/Target/PowerPC/README_ALTIVEC.txt
index 9de4415c3e0c39dd2da3752872f04d0a659a5154..1e2cfaa04dedd51cbd5f6db8a17a3bd96338c8d6 100644 (file)
--- a/lib/Target/PowerPC/README_ALTIVEC.txt
+++ b/lib/Target/PowerPC/README_ALTIVEC.txt
@@ -39,16 +39,12 @@ a load/store/lve*x sequence.
 
 //===----------------------------------------------------------------------===//
 
-FABS/FNEG can be codegen'd with the appropriate and/xor of -0.0.
-
-//===----------------------------------------------------------------------===//
-
 For functions that use altivec AND have calls, we are VRSAVE'ing all call
 clobbered regs.
 
 //===----------------------------------------------------------------------===//
 
-Implement passing vectors by value.
+Implement passing vectors by value into calls and receiving them as arguments.
 
 //===----------------------------------------------------------------------===//
 
@@ -57,13 +53,6 @@ of C1/C2/C3, then a load and vperm of Variable.
 
 //===----------------------------------------------------------------------===//
 
-We currently codegen SCALAR_TO_VECTOR as a store of the scalar to a 16-byte
-aligned stack slot, followed by a load/vperm.  We should probably just store it
-to a scalar stack slot, then use lvsl/vperm to load it.  If the value is already
-in memory, this is a huge win.
-
-//===----------------------------------------------------------------------===//
-
 Do not generate the MFCR/RLWINM sequence for predicate compares when the
 predicate compare is used immediately by a branch.  Just branch on the right
 cond code on CR6.
@@ -75,6 +64,13 @@ be constants.  The verifier should enforce this constraint.
 
 //===----------------------------------------------------------------------===//
 
+We currently codegen SCALAR_TO_VECTOR as a store of the scalar to a 16-byte
+aligned stack slot, followed by a load/vperm.  We should probably just store it
+to a scalar stack slot, then use lvsl/vperm to load it.  If the value is already
+in memory this is a big win.
+
+//===----------------------------------------------------------------------===//
+
 extract_vector_elt of an arbitrary constant vector can be done with the 
 following instructions:
 
@@ -87,8 +83,9 @@ We can do an arbitrary non-constant value by using lvsr/perm/ste.
 
 If we want to tie instruction selection into the scheduler, we can do some
 constant formation with different instructions.  For example, we can generate
-"vsplti -1" with "vcmpequw R,R" and 1,1,1,1 with "vsubcuw R,R", both of which
-use different execution units, thus could help scheduling.
+"vsplti -1" with "vcmpequw R,R" and 1,1,1,1 with "vsubcuw R,R", and 0,0,0,0 with
+"vsplti 0" or "vxor", each of which use different execution units, thus could
+help scheduling.
 
 This is probably only reasonable for a post-pass scheduler.