[PATCH] AArch64: Relax assert about large shift sizes.

[Phabricator]

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D6940

Files:
  llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
  llvm/trunk/test/CodeGen/AArch64/large_shift.ll

Index: llvm/trunk/test/CodeGen/AArch64/large_shift.ll
===================================================================
--- llvm/trunk/test/CodeGen/AArch64/large_shift.ll
+++ llvm/trunk/test/CodeGen/AArch64/large_shift.ll
@@ -0,0 +1,21 @@
+; RUN: llc -march=aarch64 -o - %s
+target triple = "arm64-unknown-unknown"
+
+; Make sure we don't run into an assert in the aarch64 code selection when
+; DAGCombining fails.
+
+declare void @t()
+
+define void @foo() {
+  %c = bitcast i64 270458 to i64
+  %t0 = lshr i64 %c, 422383
+  %t1 = trunc i64 %t0 to i1
+  br i1 %t1, label %BB1, label %BB0
+
+BB0:
+  call void @t()
+  br label %BB1
+
+BB1:
+  ret void
+}
Index: llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
@@ -1397,8 +1397,10 @@
   } else
     return false;
 
-  assert((BiggerPattern || (Srl_imm > 0 && Srl_imm < VT.getSizeInBits())) &&
-         "bad amount in shift node!");
+  // Bail out on large immediates. This happens when no proper
+  // combining/constant folding was performed.
+  if (!BiggerPattern && (Srl_imm <= 0 || Srl_imm >= VT.getSizeInBits()))
+    return false;
 
   LSB = Srl_imm;
   MSB = Srl_imm + (VT == MVT::i32 ? countTrailingOnes<uint32_t>(And_imm)
@@ -1502,7 +1504,11 @@
   } else
     return false;
 
-  assert(Shl_imm < VT.getSizeInBits() && "bad amount in shift node!");
+  // Missing combines/constant folding may have left us with strange
+  // constants.
+  if (Shl_imm >= VT.getSizeInBits())
+    return false;
+
   uint64_t Srl_imm = 0;
   if (!isIntImmediate(N->getOperand(1), Srl_imm))
     return false;

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