SimplifyCFG: Track the number of used icmps when turning a icmp chain into a switch. If we used only one icmp, don't turn it into a switch.

Also prevent the switch-to-icmp transform from creating identity adds, noticed by Marius Wachtler.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125056 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SimplifyCFG/switch-to-icmp.ll

@@ -16,8 +16,8 @@ lor.end:
  ret i1 %0
 
 ; CHECK: @test1
-; CHECK: %off = add i32 %x, -1
-; CHECK: %switch = icmp ult i32 %off, 3
+; CHECK: %x.off = add i32 %x, -1
+; CHECK: %switch = icmp ult i32 %x.off, 3
 }
 
 define zeroext i1 @test2(i32 %x) nounwind readnone ssp noredzone {
@@ -35,6 +35,5 @@ lor.end:
  ret i1 %0
 
 ; CHECK: @test2
-; CHECK: %off = add i32 %x, 0
-; CHECK: %switch = icmp ult i32 %off, 2
+; CHECK: %switch = icmp ult i32 %x, 2
 }

test/Transforms/SimplifyCFG/switch_create.ll

@@ -141,8 +141,8 @@ UnifiedReturnBlock:             ; preds = %shortcirc_done.4, %shortcirc_next.4
         ret i1 %UnifiedRetVal
         
 ; CHECK: @test6
-; CHECK: %off = add i32 %tmp.2.i, -14
-; CHECK: %switch = icmp ult i32 %off, 6
+; CHECK: %tmp.2.i.off = add i32 %tmp.2.i, -14
+; CHECK: %switch = icmp ult i32 %tmp.2.i.off, 6
 }
 
 define void @test7(i8 zeroext %c, i32 %x) nounwind ssp noredzone {
@@ -441,8 +441,8 @@ if.end:
 define zeroext i1 @test16(i32 %x) nounwind {
 entry:
 ; CHECK: @test16
-; CHECK: %off = add i32 %x, -1
-; CHECK: %switch = icmp ult i32 %off, 3
+; CHECK: %x.off = add i32 %x, -1
+; CHECK: %switch = icmp ult i32 %x.off, 3
   %cmp.i = icmp eq i32 %x, 1
   br i1 %cmp.i, label %lor.end, label %lor.lhs.false
 
@@ -458,3 +458,24 @@ lor.end:
   %0 = phi i1 [ true, %lor.lhs.false ], [ true, %entry ], [ %cmp.i1, %lor.rhs ]
   ret i1 %0
 }
+
+; Check that we don't turn an icmp into a switch where it's not useful.
+define void @test17(i32 %x, i32 %y) {
+  %cmp = icmp ult i32 %x, 3
+  %switch = icmp ult i32 %y, 2
+  %or.cond775 = or i1 %cmp, %switch
+  br i1 %or.cond775, label %lor.lhs.false8, label %return
+
+lor.lhs.false8:
+  tail call void @foo1()
+  ret void
+
+return:
+  ret void
+
+; CHECK: @test17
+; CHECK-NOT: switch.early.test
+; CHECK-NOT: switch i32
+; CHECK: ret void
+}
+

test/Transforms/SimplifyCFG/switch_formation.dbg.ll

@@ -14,8 +14,8 @@ declare void @llvm.dbg.stoppoint(i32, i32, { }*) nounwind
 
 define i1 @t({ i32, i32 }* %I) {
 ; CHECK: @t
-; CHECK: %off = add i32 %tmp.2.i, -14
-; CHECK: %switch = icmp ult i32 %off, 6
+; CHECK: %tmp.2.i.off = add i32 %tmp.2.i, -14
+; CHECK: %switch = icmp ult i32 %tmp.2.i.off, 6
 entry:
         %tmp.1.i = getelementptr { i32, i32 }* %I, i64 0, i32 1         ; <i32*> [#uses=1]
         %tmp.2.i = load i32* %tmp.1.i           ; <i32> [#uses=6]