Add a convenience method to copy wrapping, exact, and fast-math flags (NFC).

The loop vectorizer preserves wrapping, exact, and fast-math properties of scalar instructions.
This patch adds a convenience method to make that operation easier because we need to do this
in the loop vectorizer, SLP vectorizer, and possibly other places.

Although this is a 'no functional change' patch, I've added a testcase to verify that the exact
flag is preserved by the loop vectorizer. The wrapping and fast-math flags are already checked
in existing testcases.

Differential Revision: http://reviews.llvm.org/D5138

llvm-svn: 216886

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/exact.ll b/llvm/test/Transforms/LoopVectorize/exact.ll
new file mode 100644
index 00000000000..0a8fbf33734
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/exact.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s  -loop-vectorize -force-vector-width=4 -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+; CHECK-LABEL: @lshr_exact(
+; CHECK: lshr exact <4 x i32>
+define void @lshr_exact(i32* %x) {
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32* %x, i64 %iv
+  %0 = load i32* %arrayidx, align 4
+  %conv1 = lshr exact i32 %0, 1
+  store i32 %conv1, i32* %arrayidx, align 4
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond = icmp eq i64 %iv.next, 256
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}