Fold certain additions through selects (and their compares) so as to eliminate subtractions. This code is often produced by the SMAX expansion in SCEV.

This implements test/Transforms/InstCombine/2007-12-18-AddSelCmpSub.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45158 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 38 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/2007-12-18-AddSelCmpSub.ll b/test/Transforms/InstCombine/2007-12-18-AddSelCmpSub.ll
new file mode 100644
index 0000000000..ef38eee30e
--- /dev/null
+++ b/test/Transforms/InstCombine/2007-12-18-AddSelCmpSub.ll
@@ -0,0 +1,38 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {sub}
+
+define i32 @foo(i32 %a) {
+entry:
+        %tmp15 = sub i32 99, %a         ; <i32> [#uses=2]
+        %tmp16 = icmp slt i32 %tmp15, 0         ; <i1> [#uses=1]
+        %smax = select i1 %tmp16, i32 0, i32 %tmp15             ; <i32> [#uses=1]
+        %tmp12 = add i32 %smax, %a              ; <i32> [#uses=1]
+        %tmp13 = add i32 %tmp12, 1              ; <i32> [#uses=1]
+        ret i32 %tmp13
+}
+
+define i32 @bar(i32 %a) {
+entry:
+        %tmp15 = sub i32 99, %a         ; <i32> [#uses=2]
+        %tmp16 = icmp slt i32 %tmp15, 0         ; <i1> [#uses=1]
+        %smax = select i1 %tmp16, i32 0, i32 %tmp15             ; <i32> [#uses=1]
+        %tmp12 = add i32 %smax, %a              ; <i32> [#uses=1]
+        ret i32 %tmp12
+}
+
+define i32 @baz(i32 %a) {
+entry:
+        %tmp15 = sub i32 99, %a         ; <i32> [#uses=1]
+        %tmp16 = icmp slt i32 %tmp15, 0         ; <i1> [#uses=1]
+        %smax = select i1 %tmp16, i32 0, i32 42             ; <i32> [#uses=1]
+        %tmp12 = add i32 %smax, %a              ; <i32> [#uses=1]
+        ret i32 %tmp12
+}
+
+define i32 @fun(i32 %a) {
+entry:
+        %tmp15 = sub i32 99, %a         ; <i32> [#uses=1]
+        %tmp16 = icmp slt i32 %a, 0         ; <i1> [#uses=1]
+        %smax = select i1 %tmp16, i32 0, i32 %tmp15             ; <i32> [#uses=1]
+        %tmp12 = add i32 %smax, %a              ; <i32> [#uses=1]
+        ret i32 %tmp12
+}
\ No newline at end of file