[llvm-commits] [llvm] r105406 - in /llvm/trunk: lib/CodeGen/SelectionDAG/TargetLowering.cpp test/CodeGen/X86/promote-assert-zext.ll

[Dan Gohman]

Author: djg
Date: Thu Jun  3 15:21:33 2010
New Revision: 105406

URL: http://llvm.org/viewvc/llvm-project?rev=105406&view=rev
Log:
Fix SimplifyDemandedBits' AssertZext logic to demand all the bits. It
needs to demand the high bits because it's asserting that they're zero.

Added:
    llvm/trunk/test/CodeGen/X86/promote-assert-zext.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp?rev=105406&r1=105405&r2=105406&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp Thu Jun  3 15:21:33 2010
@@ -1498,13 +1498,17 @@
     break;
   }
   case ISD::AssertZext: {
-    EVT VT = cast<VTSDNode>(Op.getOperand(1))->getVT();
-    APInt InMask = APInt::getLowBitsSet(BitWidth,
-                                        VT.getSizeInBits());
-    if (SimplifyDemandedBits(Op.getOperand(0), InMask & NewMask,
+    // Demand all the bits of the input that are demanded in the output.
+    // The low bits are obvious; the high bits are demanded because we're
+    // asserting that they're zero here.
+    if (SimplifyDemandedBits(Op.getOperand(0), NewMask,
                              KnownZero, KnownOne, TLO, Depth+1))
       return true;
     assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); 
+
+    EVT VT = cast<VTSDNode>(Op.getOperand(1))->getVT();
+    APInt InMask = APInt::getLowBitsSet(BitWidth,
+                                        VT.getSizeInBits());
     KnownZero |= ~InMask & NewMask;
     break;
   }

Added: llvm/trunk/test/CodeGen/X86/promote-assert-zext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/promote-assert-zext.ll?rev=105406&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/promote-assert-zext.ll (added)
+++ llvm/trunk/test/CodeGen/X86/promote-assert-zext.ll Thu Jun  3 15:21:33 2010
@@ -0,0 +1,22 @@
+; RUN: llc < %s | FileCheck %s
+; rdar://8051990
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin11"
+
+; ISel doesn't yet know how to eliminate this extra zero-extend. But until
+; it knows how to do so safely, it shouldn;t eliminate it.
+; CHECK: movzbl  (%rdi), %eax
+; CHECK: movzwl  %ax, %eax
+
+define i64 @_ZL5matchPKtPKhiR9MatchData(i8* %tmp13) nounwind {
+entry:
+  %tmp14 = load i8* %tmp13, align 1
+  %tmp17 = zext i8 %tmp14 to i16
+  br label %bb341
+
+bb341:
+  %tmp18 = add i16 %tmp17, -1
+  %tmp23 = sext i16 %tmp18 to i64
+  ret i64 %tmp23
+}