Fix PR13412, a nasty miscompile due to the interleaved

instsimplify+inline strategy.

The crux of the problem is that instsimplify was reasonably relying on
an invariant that is true within any single function, but is no longer
true mid-inline the way we use it. This invariant is that an argument
pointer != a local (alloca) pointer.

The fix is really light weight though, and allows instsimplify to be
resiliant to these situations: when checking the relation ships to
function arguments, ensure that the argumets come from the same
function. If they come from different functions, then none of these
assumptions hold. All credit to Benjamin Kramer for coming up with this
clever solution to the problem.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161410 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 62 insertions, 0 deletions

diff --git a/test/Transforms/Inline/inline_constprop.ll b/test/Transforms/Inline/inline_constprop.ll
index dc35b60ba3..0b48a7282f 100644
--- a/test/Transforms/Inline/inline_constprop.ll
+++ b/test/Transforms/Inline/inline_constprop.ll
@@ -110,3 +110,65 @@ bb.merge:
 bb.false:
   ret i32 %sub
 }
+
+
+define i32 @PR13412.main() {
+; This is a somewhat complicated three layer subprogram that was reported to
+; compute the wrong value for a branch due to assuming that an argument
+; mid-inline couldn't be equal to another pointer.
+;
+; After inlining, the branch should point directly to the exit block, not to
+; the intermediate block.
+; CHECK: @PR13412.main
+; CHECK: br i1 true, label %[[TRUE_DEST:.*]], label %[[FALSE_DEST:.*]]
+; CHECK: [[FALSE_DEST]]:
+; CHECK-NEXT: call void @PR13412.fail()
+; CHECK: [[TRUE_DEST]]:
+; CHECK-NEXT: ret i32 0
+
+entry:
+  %i1 = alloca i64
+  store i64 0, i64* %i1
+  %arraydecay = bitcast i64* %i1 to i32*
+  %call = call i1 @PR13412.first(i32* %arraydecay, i32* %arraydecay)
+  br i1 %call, label %cond.end, label %cond.false
+
+cond.false:
+  call void @PR13412.fail()
+  br label %cond.end
+
+cond.end:
+  ret i32 0
+}
+
+define internal i1 @PR13412.first(i32* %a, i32* %b) {
+entry:
+  %call = call i32* @PR13412.second(i32* %a, i32* %b)
+  %cmp = icmp eq i32* %call, %b
+  ret i1 %cmp
+}
+
+declare void @PR13412.fail()
+
+define internal i32* @PR13412.second(i32* %a, i32* %b) {
+entry:
+  %sub.ptr.lhs.cast = ptrtoint i32* %b to i64
+  %sub.ptr.rhs.cast = ptrtoint i32* %a to i64
+  %sub.ptr.sub = sub i64 %sub.ptr.lhs.cast, %sub.ptr.rhs.cast
+  %sub.ptr.div = ashr exact i64 %sub.ptr.sub, 2
+  %cmp = icmp ugt i64 %sub.ptr.div, 1
+  br i1 %cmp, label %if.then, label %if.end3
+
+if.then:
+  %0 = load i32* %a
+  %1 = load i32* %b
+  %cmp1 = icmp eq i32 %0, %1
+  br i1 %cmp1, label %return, label %if.end3
+
+if.end3:
+  br label %return
+
+return:
+  %retval.0 = phi i32* [ %b, %if.end3 ], [ %a, %if.then ]
+  ret i32* %retval.0
+}