add support for PIC on linux x86-64

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

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 5d7d8c30be6724412dc65ae01f49fd13928f837f..23572cd6bc58f1f0bda5cd7be10e25da07c8b50a 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -317,11 +317,6 @@ this construct.
 
 //===---------------------------------------------------------------------===//
 
-Instcombine misses several of these cases (see the testcase in the patch):
-http://gcc.gnu.org/ml/gcc-patches/2006-10/msg01519.html
-
-//===---------------------------------------------------------------------===//
-
 viterbi speeds up *significantly* if the various "history" related copy loops
 are turned into memcpy calls at the source level.  We need a "loops to memcpy"
 pass.
@@ -772,3 +767,20 @@ ARM, we end up with calls to L___lshrdi3/L___ashldi3 in f, which is
 badness.  PPC64 misses f, f5 and f6.  CellSPU aborts in isel.
 
 //===---------------------------------------------------------------------===//
+
+We do a number of simplifications in simplify libcalls to strength reduce
+standard library functions, but we don't currently merge them together.  For
+example, it is useful to merge memcpy(a,b,strlen(b)) -> strcpy.  This can only
+be done safely if "b" isn't modified between the strlen and memcpy of course.
+
+//===---------------------------------------------------------------------===//
+
+We should be able to evaluate this loop:
+
+int test(int x_offs) {
+  while (x_offs > 4)
+     x_offs -= 4;
+  return x_offs;
+}
+
+//===---------------------------------------------------------------------===//