[PhaseOrdering] add test for funnel shift (rotate); NFC

As mentioned in D55604, there are 2 bugs here:
1. The new pass manager is speculating wildly by default.
2. The old pass manager is not converting this to funnel shift.

llvm-svn: 348980

llvm/test/Transforms/PhaseOrdering/rotate.ll

@@ -0,0 +1,49 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -O3 -S < %s                    | FileCheck %s --check-prefixes=ANY,OLDPM
+; RUN: opt -passes='default<O3>' -S < %s  | FileCheck %s --check-prefixes=ANY,NEWPM
+
+; This should become a single funnel shift through a combination
+; of aggressive-instcombine, simplifycfg, and instcombine.
+; https://bugs.llvm.org/show_bug.cgi?id=34924
+
+define i32 @rotl(i32 %a, i32 %b) {
+; OLDPM-LABEL: @rotl(
+; OLDPM-NEXT:  entry:
+; OLDPM-NEXT:    [[CMP:%.*]] = icmp eq i32 [[B:%.*]], 0
+; OLDPM-NEXT:    br i1 [[CMP]], label [[END:%.*]], label [[ROTBB:%.*]]
+; OLDPM:       rotbb:
+; OLDPM-NEXT:    [[SUB:%.*]] = sub i32 32, [[B]]
+; OLDPM-NEXT:    [[SHR:%.*]] = lshr i32 [[A:%.*]], [[SUB]]
+; OLDPM-NEXT:    [[SHL:%.*]] = shl i32 [[A]], [[B]]
+; OLDPM-NEXT:    [[OR:%.*]] = or i32 [[SHR]], [[SHL]]
+; OLDPM-NEXT:    br label [[END]]
+; OLDPM:       end:
+; OLDPM-NEXT:    [[COND:%.*]] = phi i32 [ [[OR]], [[ROTBB]] ], [ [[A]], [[ENTRY:%.*]] ]
+; OLDPM-NEXT:    ret i32 [[COND]]
+;
+; NEWPM-LABEL: @rotl(
+; NEWPM-NEXT:  entry:
+; NEWPM-NEXT:    [[TMP0:%.*]] = sub i32 0, [[B:%.*]]
+; NEWPM-NEXT:    [[TMP1:%.*]] = and i32 [[B]], 31
+; NEWPM-NEXT:    [[TMP2:%.*]] = and i32 [[TMP0]], 31
+; NEWPM-NEXT:    [[TMP3:%.*]] = lshr i32 [[A:%.*]], [[TMP2]]
+; NEWPM-NEXT:    [[TMP4:%.*]] = shl i32 [[A]], [[TMP1]]
+; NEWPM-NEXT:    [[SPEC_SELECT:%.*]] = or i32 [[TMP3]], [[TMP4]]
+; NEWPM-NEXT:    ret i32 [[SPEC_SELECT]]
+;
+entry:
+  %cmp = icmp eq i32 %b, 0
+  br i1 %cmp, label %end, label %rotbb
+
+rotbb:
+  %sub = sub i32 32, %b
+  %shr = lshr i32 %a, %sub
+  %shl = shl i32 %a, %b
+  %or = or i32 %shr, %shl
+  br label %end
+
+end:
+  %cond = phi i32 [ %or, %rotbb ], [ %a, %entry ]
+  ret i32 %cond
+}
+