Add an instcombine for constructs like a | -(b != c); a select is more

canonical, and generally leads to better code.  Found while looking at
an article about saturating arithmetic.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129545 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstCombine/or.ll

@@ -390,3 +390,22 @@ define i1 @test36(i32 %x) {
 ; CHECK-NEXT: ret i1
 }
 
+define i32 @test37(i32* %xp, i32 %y) {
+; CHECK: @test37
+; CHECK: select i1 %tobool, i32 -1, i32 %x
+  %tobool = icmp ne i32 %y, 0
+  %sext = sext i1 %tobool to i32
+  %x = load i32* %xp
+  %or = or i32 %sext, %x
+  ret i32 %or
+}
+
+define i32 @test38(i32* %xp, i32 %y) {
+; CHECK: @test38
+; CHECK: select i1 %tobool, i32 -1, i32 %x
+  %tobool = icmp ne i32 %y, 0
+  %sext = sext i1 %tobool to i32
+  %x = load i32* %xp
+  %or = or i32 %x, %sext
+  ret i32 %or
+}