[llvm] r230355 - AArch64: Relax assert about large shift sizes.

Matthias Braun matze at braunis.de
Tue Feb 24 10:52:04 PST 2015


Author: matze
Date: Tue Feb 24 12:52:04 2015
New Revision: 230355

URL: http://llvm.org/viewvc/llvm-project?rev=230355&view=rev
Log:
AArch64: Relax assert about large shift sizes.

The reason why these large shift sizes happen is because OpaqueConstants
currently inhibit alot of DAG combining, but that has to be addressed in
another commit (like the proposal in D6946).

Differential Revision: http://reviews.llvm.org/D6940

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

Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp?rev=230355&r1=230354&r2=230355&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp Tue Feb 24 12:52:04 2015
@@ -1397,8 +1397,10 @@ static bool isBitfieldExtractOpFromAnd(S
   } 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 @@ static bool isBitfieldExtractOpFromShr(S
   } 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;

Added: llvm/trunk/test/CodeGen/AArch64/large_shift.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/large_shift.ll?rev=230355&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/large_shift.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/large_shift.ll Tue Feb 24 12:52:04 2015
@@ -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
+}





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