[llvm] r285480 - [DAGCombiner] Fix a crash visiting `AND` nodes.

[Davide Italiano via llvm-commits]

Author: davide
Date: Fri Oct 28 18:55:32 2016
New Revision: 285480

URL: http://llvm.org/viewvc/llvm-project?rev=285480&view=rev
Log:
[DAGCombiner] Fix a crash visiting `AND` nodes.

Instead of asserting that the shift count is != 0 we just bail out
as it's not profitable trying to optimize a node which will be
removed anyway.

Differential Revision:  https://reviews.llvm.org/D26098

Added:
    llvm/trunk/test/CodeGen/X86/pr30813.s
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=285480&r1=285479&r2=285480&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Fri Oct 28 18:55:32 2016
@@ -3046,6 +3046,11 @@ SDValue DAGCombiner::visitANDLike(SDValu
         unsigned Size = VT.getSizeInBits();
         const APInt &AndMask = CAnd->getAPIntValue();
         unsigned ShiftBits = CShift->getZExtValue();
+
+        // Bail out, this node will probably disappear anyway.
+        if (ShiftBits == 0)
+          return SDValue();
+
         unsigned MaskBits = AndMask.countTrailingOnes();
         EVT HalfVT = EVT::getIntegerVT(*DAG.getContext(), Size / 2);
 
@@ -3064,7 +3069,7 @@ SDValue DAGCombiner::visitANDLike(SDValu
           // extended to handle extensions mixed in.
 
           SDValue SL(N0);
-          assert(ShiftBits != 0 && MaskBits <= Size);
+          assert(MaskBits <= Size);
 
           // Extracting the highest bit of the low half.
           EVT ShiftVT = TLI.getShiftAmountTy(HalfVT, DAG.getDataLayout());

Added: llvm/trunk/test/CodeGen/X86/pr30813.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr30813.s?rev=285480&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr30813.s (added)
+++ llvm/trunk/test/CodeGen/X86/pr30813.s Fri Oct 28 18:55:32 2016
@@ -0,0 +1,20 @@
+	.text
+	.file	"/home/davide/work/llvm/test/CodeGen/X86/visitand-shift.ll"
+	.globl	patatino
+	.p2align	4, 0x90
+	.type	patatino, at function
+patatino:                               # @patatino
+	.cfi_startproc
+# BB#0:
+                                        # implicit-def: %RAX
+	movzwl	(%rax), %ecx
+	movl	%ecx, %eax
+                                        # implicit-def: %RDX
+	movq	%rax, (%rdx)
+	retq
+.Lfunc_end0:
+	.size	patatino, .Lfunc_end0-patatino
+	.cfi_endproc
+
+
+	.section	".note.GNU-stack","", at progbits