Reapply r108378, with bugfixes, testcase, and improved comment formatting.

This now passes LIT, nighty test, and llvm-gcc bootstrap on my machine.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108422 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstCombine/bit-checks.ll

@@ -0,0 +1,15 @@
+; This test makes sure that these instructions are properly eliminated.
+;
+; RUN: opt < %s -instcombine -S | \
+; RUN:    not grep {tobool}
+; END.
+define i32 @main(i32 %argc, i8** %argv) nounwind ssp {
+entry:
+  %and = and i32 %argc, 1                         ; <i32> [#uses=1]
+  %tobool = icmp ne i32 %and, 0                   ; <i1> [#uses=1]
+  %and2 = and i32 %argc, 2                        ; <i32> [#uses=1]
+  %tobool3 = icmp ne i32 %and2, 0                 ; <i1> [#uses=1]
+  %or.cond = and i1 %tobool, %tobool3             ; <i1> [#uses=1]
+  %retval.0 = select i1 %or.cond, i32 2, i32 1    ; <i32> [#uses=1]
+  ret i32 %retval.0
+}