[llvm-commits] [llvm] r78295 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/wide-integer-fold.ll

[Dan Gohman]

Author: djg
Date: Thu Aug  6 04:18:59 2009
New Revision: 78295

URL: http://llvm.org/viewvc/llvm-project?rev=78295&view=rev
Log:
Fix a few places in DAGCombiner that were creating all-ones-bits
and high-bits values in ways that weren't correct for integer
types wider than 64 bits. This fixes a miscompile in
PPMacroExpansion.cpp in clang on x86-64.

Added:
    llvm/trunk/test/CodeGen/X86/wide-integer-fold.ll
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=78295&r1=78294&r2=78295&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Aug  6 04:18:59 2009
@@ -1930,7 +1930,7 @@
 
   // fold (or x, undef) -> -1
   if (N0.getOpcode() == ISD::UNDEF || N1.getOpcode() == ISD::UNDEF)
-    return DAG.getConstant(~0ULL, VT);
+    return DAG.getConstant(APInt::getAllOnesValue(VT.getSizeInBits()), VT);
   // fold (or c1, c2) -> c1|c2
   if (N0C && N1C)
     return DAG.FoldConstantArithmetic(ISD::OR, VT, N0C, N1C);
@@ -2477,9 +2477,13 @@
     uint64_t c1 = cast<ConstantSDNode>(N0.getOperand(1))->getZExtValue();
     if (c1 < VT.getSizeInBits()) {
       uint64_t c2 = N1C->getZExtValue();
+      SDValue HiBitsMask =
+        DAG.getConstant(APInt::getHighBitsSet(VT.getSizeInBits(),
+                                              VT.getSizeInBits() - c1),
+                        VT);
       SDValue Mask = DAG.getNode(ISD::AND, N0.getDebugLoc(), VT,
                                  N0.getOperand(0),
-                                 DAG.getConstant(~0ULL << c1, VT));
+                                 HiBitsMask);
       if (c2 > c1)
         return DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, Mask,
                            DAG.getConstant(c2-c1, N1.getValueType()));
@@ -2489,9 +2493,15 @@
     }
   }
   // fold (shl (sra x, c1), c1) -> (and x, (shl -1, c1))
-  if (N1C && N0.getOpcode() == ISD::SRA && N1 == N0.getOperand(1))
+  if (N1C && N0.getOpcode() == ISD::SRA && N1 == N0.getOperand(1)) {
+    SDValue HiBitsMask =
+      DAG.getConstant(APInt::getHighBitsSet(VT.getSizeInBits(),
+                                            VT.getSizeInBits() -
+                                              N1C->getZExtValue()),
+                      VT);
     return DAG.getNode(ISD::AND, N->getDebugLoc(), VT, N0.getOperand(0),
-                       DAG.getConstant(~0ULL << N1C->getZExtValue(), VT));
+                       HiBitsMask);
+  }
 
   return N1C ? visitShiftByConstant(N, N1C->getZExtValue()) : SDValue();
 }
@@ -3094,9 +3104,11 @@
     }
     
     // sext(setcc x, y, cc) -> (select_cc x, y, -1, 0, cc)
+    SDValue NegOne =
+      DAG.getConstant(APInt::getAllOnesValue(VT.getSizeInBits()), VT);
     SDValue SCC =
       SimplifySelectCC(N->getDebugLoc(), N0.getOperand(0), N0.getOperand(1),
-                       DAG.getConstant(~0ULL, VT), DAG.getConstant(0, VT),
+                       NegOne, DAG.getConstant(0, VT),
                        cast<CondCodeSDNode>(N0.getOperand(2))->get(), true);
     if (SCC.getNode()) return SCC;
   }

Added: llvm/trunk/test/CodeGen/X86/wide-integer-fold.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/wide-integer-fold.ll?rev=78295&view=auto

==============================================================================
--- llvm/trunk/test/CodeGen/X86/wide-integer-fold.ll (added)
+++ llvm/trunk/test/CodeGen/X86/wide-integer-fold.ll Thu Aug  6 04:18:59 2009
@@ -0,0 +1,12 @@
+; RUN: llvm-as < %s | llc -march=x86-64 | FileCheck %s
+; CHECK:  movq  $-65535, %rax
+
+; DAGCombiner should fold this to a simple constant.
+
+define i64 @foo(i192 %a) nounwind {
+  %t = or i192 %a, -22300404916163702203072254898040925442801665
+  %s = and i192 %t, -22300404916163702203072254898040929737768960
+  %u = lshr i192 %s, 128
+  %v = trunc i192 %u to i64
+  ret i64 %v
+}