Reapplying [FastISel][AArch64] Cleanup constant materialization code. NFCI.

[oota-llvm.git] / lib / Target / X86 / README-SSE.txt

diff --git a/lib/Target/X86/README-SSE.txt b/lib/Target/X86/README-SSE.txt
index 496b704ee85fb16878eb8585a77121b78497a674..71329b06692359fab36adf01fa6083406df60603 100644 (file)
--- a/lib/Target/X86/README-SSE.txt
+++ b/lib/Target/X86/README-SSE.txt
@@ -494,11 +494,6 @@ is memory.
 
 //===---------------------------------------------------------------------===//
 
-SSE4 extract-to-mem ops aren't being pattern matched because of the AssertZext
-sitting between the truncate and the extract.
-
-//===---------------------------------------------------------------------===//
-
 INSERTPS can match any insert (extract, imm1), imm2 for 4 x float, and insert
 any number of 0.0 simultaneously.  Currently we only use it for simple
 insertions.
@@ -517,37 +512,6 @@ to <2 x i64> ops being so bad.
 
 //===---------------------------------------------------------------------===//
 
-'select' on vectors and scalars could be a whole lot better.  We currently 
-lower them to conditional branches.  On x86-64 for example, we compile this:
-
-double test(double a, double b, double c, double d) { return a<b ? c : d; }
-
-to:
-
-_test:
-       ucomisd %xmm0, %xmm1
-       ja      LBB1_2  # entry
-LBB1_1:        # entry
-       movapd  %xmm3, %xmm2
-LBB1_2:        # entry
-       movapd  %xmm2, %xmm0
-       ret
-
-instead of:
-
-_test:
-       cmpltsd %xmm1, %xmm0
-       andpd   %xmm0, %xmm2
-       andnpd  %xmm3, %xmm0
-       orpd    %xmm2, %xmm0
-       ret
-
-For unpredictable branches, the later is much more efficient.  This should
-just be a matter of having scalar sse map to SELECT_CC and custom expanding
-or iseling it.
-
-//===---------------------------------------------------------------------===//
-
 LLVM currently generates stack realignment code, when it is not necessary
 needed. The problem is that we need to know about stack alignment too early,
 before RA runs.