diff --git a/llvm/lib/CodeGen/EarlyIfConversion.cpp b/llvm/lib/CodeGen/EarlyIfConversion.cpp
--- a/llvm/lib/CodeGen/EarlyIfConversion.cpp
+++ b/llvm/lib/CodeGen/EarlyIfConversion.cpp
@@ -52,6 +52,12 @@
 static cl::opt<bool> Stress("stress-early-ifcvt", cl::Hidden,
   cl::desc("Turn all knobs to 11"));
 
+// Absolute maximum number of instructions allowed per speculated block.
+// This bypasses all other heuristics, so it should be set fairly high.
+static cl::opt<bool> AllowPredicatingTwice(
+    "allow-predicating-twice", cl::init(false), cl::Hidden,
+    cl::desc("Allow predicating already predicated code."));
+
 STATISTIC(NumDiamondsSeen,  "Number of diamonds");
 STATISTIC(NumDiamondsConv,  "Number of diamonds converted");
 STATISTIC(NumTrianglesSeen, "Number of triangles");
@@ -321,9 +327,15 @@
       return false;
     }
 
-    // Check that instruction is predicable and that it is not already
-    // predicated.
-    if (!TII->isPredicable(*I) || TII->isPredicated(*I)) {
+    // Check that instruction is predicable
+    if (!TII->isPredicable(*I)) {
+      LLVM_DEBUG(dbgs() << "Isn't predicable: " << *I);
+      return false;
+    }
+
+    // Check that instruction is not already predicated.
+    if (!AllowPredicatingTwice && TII->isPredicated(*I)) {
+      LLVM_DEBUG(dbgs() << "Is already predicated: " << *I);
       return false;
     }