Exploit distributive laws (eg: And distributes over Or, Mul over Add, etc) in a

fairly systematic way in instcombine.  Some of these cases were already dealt
with, in which case I removed the existing code.  The case of Add has a bunch of
funky logic which covers some of this plus a few variants (considers shifts to be
a form of multiplication), which I didn't touch.  The simplification performed is:
A*B+A*C -> A*(B+C).  The improvement is to do this in cases that were not already
handled [such as A*B-A*C -> A*(B-C), which was reported on the mailing list], and
also to do it more often by not checking for "only one use" if "B+C" simplifies.

llvm-svn: 120024

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/2010-11-23-Distributed.ll b/llvm/test/Transforms/InstCombine/2010-11-23-Distributed.ll
new file mode 100644
index 00000000000..13a5720dad2
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/2010-11-23-Distributed.ll
@@ -0,0 +1,11 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+define i32 @foo(i32 %x, i32 %y) {
+; CHECK: @foo
+  %add = add nsw i32 %y, %x
+  %mul = mul nsw i32 %add, %y
+  %square = mul nsw i32 %y, %y
+  %res = sub i32 %mul, %square
+; CHECK: %res = mul i32 %x, %y
+  ret i32 %res
+; CHECK: ret i32 %res
+}