Don't crash on extra evil irreducible control flow.

When the CFG contains a loop with multiple entry blocks, the traces
computed by MachineTraceMetrics don't always have the same nice
properties. Loop back-edges are normally excluded from traces, but
MachineLoopInfo doesn't recognize loops with multiple entry blocks, so
those back-edges may be included.

Avoid asserting when that happens by adding an isEarlierInSameTrace()
function that accurately determines if a dominating block is part of the
same trace AND is above the currrent block in the trace.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165434 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 75 insertions, 0 deletions

diff --git a/test/CodeGen/X86/early-ifcvt.ll b/test/CodeGen/X86/early-ifcvt.ll
index 17b3cb22cd..2e1852d3e3 100644
--- a/test/CodeGen/X86/early-ifcvt.ll
+++ b/test/CodeGen/X86/early-ifcvt.ll
@@ -67,3 +67,78 @@ if.end41:
 }
 
 declare void @fprintf(...) nounwind
+
+; CHECK: BZ2_decompress
+; This test case contains irreducible control flow, so MachineLoopInfo doesn't
+; recognize the cycle in the CFG. This would confuse MachineTraceMetrics.
+define void @BZ2_decompress(i8* %s) nounwind ssp {
+entry:
+  switch i32 undef, label %sw.default [
+    i32 39, label %if.end.sw.bb2050_crit_edge
+    i32 36, label %sw.bb1788
+    i32 37, label %if.end.sw.bb1855_crit_edge
+    i32 40, label %sw.bb2409
+    i32 38, label %sw.bb1983
+    i32 44, label %if.end.sw.bb3058_crit_edge
+  ]
+
+if.end.sw.bb3058_crit_edge:                       ; preds = %entry
+  br label %save_state_and_return
+
+if.end.sw.bb1855_crit_edge:                       ; preds = %entry
+  br label %save_state_and_return
+
+if.end.sw.bb2050_crit_edge:                       ; preds = %entry
+  br label %sw.bb2050
+
+sw.bb1788:                                        ; preds = %entry
+  br label %save_state_and_return
+
+sw.bb1983:                                        ; preds = %entry
+  br i1 undef, label %save_state_and_return, label %if.then1990
+
+if.then1990:                                      ; preds = %sw.bb1983
+  br label %while.body2038
+
+while.body2038:                                   ; preds = %sw.bb2050, %if.then1990
+  %groupPos.8 = phi i32 [ 0, %if.then1990 ], [ %groupPos.9, %sw.bb2050 ]
+  br i1 undef, label %save_state_and_return, label %if.end2042
+
+if.end2042:                                       ; preds = %while.body2038
+  br i1 undef, label %if.end2048, label %while.end2104
+
+if.end2048:                                       ; preds = %if.end2042
+  %bsLive2054.pre = getelementptr inbounds i8* %s, i32 8
+  br label %sw.bb2050
+
+sw.bb2050:                                        ; preds = %if.end2048, %if.end.sw.bb2050_crit_edge
+  %groupPos.9 = phi i32 [ 0, %if.end.sw.bb2050_crit_edge ], [ %groupPos.8, %if.end2048 ]
+  %and2064 = and i32 undef, 1
+  br label %while.body2038
+
+while.end2104:                                    ; preds = %if.end2042
+  br i1 undef, label %save_state_and_return, label %if.end2117
+
+if.end2117:                                       ; preds = %while.end2104
+  br i1 undef, label %while.body2161.lr.ph, label %while.body2145.lr.ph
+
+while.body2145.lr.ph:                             ; preds = %if.end2117
+  br label %save_state_and_return
+
+while.body2161.lr.ph:                             ; preds = %if.end2117
+  br label %save_state_and_return
+
+sw.bb2409:                                        ; preds = %entry
+  br label %save_state_and_return
+
+sw.default:                                       ; preds = %entry
+  call void @BZ2_bz__AssertH__fail() nounwind
+  br label %save_state_and_return
+
+save_state_and_return:
+  %groupPos.14 = phi i32 [ 0, %sw.default ], [ %groupPos.8, %while.body2038 ], [ %groupPos.8, %while.end2104 ], [ 0, %if.end.sw.bb3058_crit_edge ], [ 0, %if.end.sw.bb1855_crit_edge ], [ %groupPos.8, %while.body2161.lr.ph ], [ %groupPos.8, %while.body2145.lr.ph ], [ 0, %sw.bb2409 ], [ 0, %sw.bb1788 ], [ 0, %sw.bb1983 ]
+  store i32 %groupPos.14, i32* undef, align 4
+  ret void
+}
+
+declare void @BZ2_bz__AssertH__fail()