[llvm-commits] CVS: llvm/lib/Target/README.txt

[Chris Lattner]

Changes in directory llvm/lib/Target:

README.txt updated: 1.9 -> 1.10
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Log message:

add a note


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Diffs of the changes:  (+15 -0)

 README.txt |   15 +++++++++++++++
 1 files changed, 15 insertions(+)


Index: llvm/lib/Target/README.txt
diff -u llvm/lib/Target/README.txt:1.9 llvm/lib/Target/README.txt:1.10
--- llvm/lib/Target/README.txt:1.9	Thu Mar  2 16:34:38 2006
+++ llvm/lib/Target/README.txt	Fri Mar  3 19:19:34 2006
@@ -86,3 +86,18 @@
 into:
 int f(int a, int b) { return a * (a + 2 * b) + b * b; }
 to eliminate a multiply.
+
+//===---------------------------------------------------------------------===//
+
+On targets with expensive 64-bit multiply, we could LSR this:
+
+for (i = ...; ++i) {
+   x = 1ULL << i;
+
+into:
+ long long tmp = 1;
+ for (i = ...; ++i, tmp+=tmp)
+   x = tmp;
+
+This would be a win on ppc32, but not x86 or ppc64.
+