enhance vmcore to know that udiv's can be exact, and add a trivial

instcombine xform to exercise this.

Nothing forms exact udivs yet though.  This is progress on PR8862



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124992 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 60 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/exact.ll b/test/Transforms/InstCombine/exact.ll
new file mode 100644
index 0000000000..940469ea71
--- /dev/null
+++ b/test/Transforms/InstCombine/exact.ll
@@ -0,0 +1,60 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; CHECK: define i32 @foo
+; CHECK: sdiv i32 %x, 8
+define i32 @foo(i32 %x) {
+  %y = sdiv i32 %x, 8
+  ret i32 %y
+}
+
+; CHECK: define i32 @bar
+; CHECK: ashr i32 %x, 3
+define i32 @bar(i32 %x) {
+  %y = sdiv exact i32 %x, 8
+  ret i32 %y
+}
+
+; CHECK: i32 @a0
+; CHECK: %y = srem i32 %x, 3
+; CHECK: %z = sub i32 %x, %y
+; CHECK: ret i32 %z
+define i32 @a0(i32 %x) {
+  %y = sdiv i32 %x, 3
+  %z = mul i32 %y, 3
+  ret i32 %z
+}
+
+; CHECK: i32 @b0
+; CHECK: ret i32 %x
+define i32 @b0(i32 %x) {
+  %y = sdiv exact i32 %x, 3
+  %z = mul i32 %y, 3
+  ret i32 %z
+}
+
+; CHECK: i32 @a1
+; CHECK: %y = srem i32 %x, 3
+; CHECK: %z = sub i32 %y, %x
+; CHECK: ret i32 %z
+define i32 @a1(i32 %x) {
+  %y = sdiv i32 %x, 3
+  %z = mul i32 %y, -3
+  ret i32 %z
+}
+
+; CHECK: i32 @b1
+; CHECK: %z = sub i32 0, %x
+; CHECK: ret i32 %z
+define i32 @b1(i32 %x) {
+  %y = sdiv exact i32 %x, 3
+  %z = mul i32 %y, -3
+  ret i32 %z
+}
+
+; CHECK: i32 @b2
+; CHECK: ret i32 %x
+define i32 @b2(i32 %x, i32 %w) {
+  %y = udiv exact i32 %x, %w
+  %z = mul i32 %y, %w
+  ret i32 %z
+}