More Chris-inspired JumpThreading fixes: use ConstantExpr to correctly constant-fold undef, and be more careful with its return value.

This actually exposed an infinite recursion bug in ComputeValueKnownInPredecessors which theoretically already existed (in JumpThreading's
handling of and/or of i1's), but never manifested before.  This patch adds a tracking set to prevent this case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112589 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 91 insertions, 0 deletions

diff --git a/test/Transforms/JumpThreading/2010-08-31-InfiniteRecursion.ll b/test/Transforms/JumpThreading/2010-08-31-InfiniteRecursion.ll
new file mode 100644
index 0000000..390948a
--- /dev/null
+++ b/test/Transforms/JumpThreading/2010-08-31-InfiniteRecursion.ll
@@ -0,0 +1,91 @@
+; RUN: opt < %s -jump-threading -disable-output
+; ModuleID = 'bugpoint-reduced-simplified.bc'
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.4"
+
+define void @encode_one_macroblock_highfast() nounwind ssp {
+entry:
+  switch i32 undef, label %bb13 [
+    i32 1, label %bb10
+    i32 2, label %bb12
+  ]
+
+bb10:                                             ; preds = %entry
+  unreachable
+
+bb12:                                             ; preds = %entry
+  unreachable
+
+bb13:                                             ; preds = %entry
+  br i1 undef, label %bb137, label %bb292
+
+bb137:                                            ; preds = %bb13
+  br i1 undef, label %bb150, label %bb154
+
+bb150:                                            ; preds = %bb137
+  unreachable
+
+bb154:                                            ; preds = %bb137
+  br i1 undef, label %bb292, label %bb246
+
+bb246:                                            ; preds = %bb154
+  br i1 undef, label %bb292, label %bb247
+
+bb247:                                            ; preds = %bb246
+  br i1 undef, label %bb248, label %bb292
+
+bb248:                                            ; preds = %bb247
+  br i1 undef, label %bb249, label %bb292
+
+bb249:                                            ; preds = %bb248
+  br i1 undef, label %bb254, label %bb250
+
+bb250:                                            ; preds = %bb249
+  unreachable
+
+bb254:                                            ; preds = %bb249
+  br i1 undef, label %bb292, label %bb255
+
+bb255:                                            ; preds = %bb288.bb289.loopexit_crit_edge, %bb254
+  br i1 undef, label %bb.nph.split.us, label %bb269
+
+bb.nph.split.us:                                  ; preds = %bb255
+  br i1 undef, label %bb.nph.split.us.split.us, label %bb269.us.us31
+
+bb.nph.split.us.split.us:                         ; preds = %bb.nph.split.us
+  br i1 undef, label %bb269.us.us, label %bb269.us.us.us
+
+bb269.us.us.us:                                   ; preds = %bb287.us.us.us, %bb.nph.split.us.split.us
+  %indvar = phi i64 [ %indvar.next, %bb287.us.us.us ], [ 0, %bb.nph.split.us.split.us ] ; <i64> [#uses=1]
+  %0 = icmp eq i16 undef, 0                       ; <i1> [#uses=1]
+  br i1 %0, label %bb287.us.us.us, label %bb286.us.us.us
+
+bb287.us.us.us:                                   ; preds = %bb269.us.us.us
+  %indvar.next = add i64 %indvar, 1               ; <i64> [#uses=2]
+  %exitcond = icmp eq i64 %indvar.next, 4         ; <i1> [#uses=1]
+  br i1 %exitcond, label %bb288.bb289.loopexit_crit_edge, label %bb269.us.us.us
+
+bb286.us.us.us:                                   ; preds = %bb269.us.us.us
+  unreachable
+
+bb269.us.us:                                      ; preds = %bb287.us.us, %bb.nph.split.us.split.us
+  br i1 undef, label %bb287.us.us, label %bb286.us.us
+
+bb287.us.us:                                      ; preds = %bb269.us.us
+  br i1 undef, label %bb288.bb289.loopexit_crit_edge, label %bb269.us.us
+
+bb286.us.us:                                      ; preds = %bb269.us.us
+  unreachable
+
+bb269.us.us31:                                    ; preds = %bb.nph.split.us
+  unreachable
+
+bb269:                                            ; preds = %bb255
+  unreachable
+
+bb288.bb289.loopexit_crit_edge:                   ; preds = %bb287.us.us, %bb287.us.us.us
+  br i1 undef, label %bb292, label %bb255
+
+bb292:                                            ; preds = %bb288.bb289.loopexit_crit_edge, %bb254, %bb248, %bb247, %bb246, %bb154, %bb13
+  unreachable
+}