[llvm-commits] [llvm] r109643 - in /llvm/trunk: include/llvm/Instructions.h lib/AsmParser/LLParser.cpp lib/Transforms/InstCombine/InstCombineCalls.cpp lib/VMCore/Instructions.cpp test/Assembler/align-inst-alloca.ll test/Assembler/align-inst-load.ll test/Assembler/align-inst-store.ll test/Assembler/align-inst.ll

[Dan Gohman]

Author: djg
Date: Wed Jul 28 15:12:04 2010
New Revision: 109643

URL: http://llvm.org/viewvc/llvm-project?rev=109643&view=rev
Log:
Define a maximum supported alignment value for load, store, and
alloca instructions (constrained by their internal encoding),
and add error checking for it. Fix an instcombine bug which
generated huge alignment values (null is infinitely aligned).
This fixes undefined behavior noticed by John Regehr.

Added:
    llvm/trunk/test/Assembler/align-inst-alloca.ll
    llvm/trunk/test/Assembler/align-inst-load.ll
    llvm/trunk/test/Assembler/align-inst-store.ll
    llvm/trunk/test/Assembler/align-inst.ll
Modified:
    llvm/trunk/include/llvm/Instructions.h
    llvm/trunk/lib/AsmParser/LLParser.cpp
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/trunk/lib/VMCore/Instructions.cpp

Modified: llvm/trunk/include/llvm/Instructions.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Instructions.h?rev=109643&r1=109642&r2=109643&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Instructions.h (original)
+++ llvm/trunk/include/llvm/Instructions.h Wed Jul 28 15:12:04 2010
@@ -31,6 +31,10 @@
 class LLVMContext;
 class DominatorTree;
 
+/// MaximumAlignment - This is the greatest alignment value supported by
+/// load, store, and alloca instructions.
+static const unsigned MaximumAlignment = 1u << 29;
+
 //===----------------------------------------------------------------------===//
 //                                AllocaInst Class
 //===----------------------------------------------------------------------===//

Modified: llvm/trunk/lib/AsmParser/LLParser.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLParser.cpp?rev=109643&r1=109642&r2=109643&view=diff
==============================================================================
--- llvm/trunk/lib/AsmParser/LLParser.cpp (original)
+++ llvm/trunk/lib/AsmParser/LLParser.cpp Wed Jul 28 15:12:04 2010
@@ -1154,6 +1154,8 @@
   if (ParseUInt32(Alignment)) return true;
   if (!isPowerOf2_32(Alignment))
     return Error(AlignLoc, "alignment is not a power of two");
+  if (Alignment > MaximumAlignment)
+    return Error(AlignLoc, "huge alignments are not supported yet");
   return false;
 }
 
@@ -1176,6 +1178,7 @@
     if (Lex.getKind() != lltok::kw_align)
       return Error(Lex.getLoc(), "expected metadata or 'align'");
     
+    LocTy AlignLoc = Lex.getLoc();
     if (ParseOptionalAlignment(Alignment)) return true;
   }
 

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=109643&r1=109642&r2=109643&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Wed Jul 28 15:12:04 2010
@@ -104,11 +104,15 @@
   ComputeMaskedBits(V, Mask, KnownZero, KnownOne);
   unsigned TrailZ = KnownZero.countTrailingOnes();
 
-  // LLVM doesn't support alignments larger than this currently.
+  // Avoid trouble with rediculously large TrailZ values, such as
+  // those computed from a null pointer.
   TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
 
   unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
 
+  // LLVM doesn't support alignments larger than this currently.
+  Align = std::min(Align, MaximumAlignment);
+
   if (PrefAlign > Align)
     Align = EnforceKnownAlignment(V, Align, PrefAlign);
   

Modified: llvm/trunk/lib/VMCore/Instructions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Instructions.cpp?rev=109643&r1=109642&r2=109643&view=diff
==============================================================================
--- llvm/trunk/lib/VMCore/Instructions.cpp (original)
+++ llvm/trunk/lib/VMCore/Instructions.cpp Wed Jul 28 15:12:04 2010
@@ -891,6 +891,8 @@
 
 void AllocaInst::setAlignment(unsigned Align) {
   assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
+  assert(Align <= MaximumAlignment &&
+         "Alignment is greater than MaximumAlignment!");
   setInstructionSubclassData(Log2_32(Align) + 1);
   assert(getAlignment() == Align && "Alignment representation error!");
 }
@@ -1026,8 +1028,11 @@
 
 void LoadInst::setAlignment(unsigned Align) {
   assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
+  assert(Align <= MaximumAlignment &&
+         "Alignment is greater than MaximumAlignment!");
   setInstructionSubclassData((getSubclassDataFromInstruction() & 1) |
                              ((Log2_32(Align)+1)<<1));
+  assert(getAlignment() == Align && "Alignment representation error!");
 }
 
 //===----------------------------------------------------------------------===//
@@ -1122,8 +1127,11 @@
 
 void StoreInst::setAlignment(unsigned Align) {
   assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
+  assert(Align <= MaximumAlignment &&
+         "Alignment is greater than MaximumAlignment!");
   setInstructionSubclassData((getSubclassDataFromInstruction() & 1) |
                              ((Log2_32(Align)+1) << 1));
+  assert(getAlignment() == Align && "Alignment representation error!");
 }
 
 //===----------------------------------------------------------------------===//

Added: llvm/trunk/test/Assembler/align-inst-alloca.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Assembler/align-inst-alloca.ll?rev=109643&view=auto
==============================================================================
--- llvm/trunk/test/Assembler/align-inst-alloca.ll (added)
+++ llvm/trunk/test/Assembler/align-inst-alloca.ll Wed Jul 28 15:12:04 2010
@@ -0,0 +1,6 @@
+; RUN: not llvm-as %s -o /dev/null 2>/dev/null
+
+define void @foo() {
+  %p = alloca i1, align 1073741824
+  ret void
+}

Added: llvm/trunk/test/Assembler/align-inst-load.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Assembler/align-inst-load.ll?rev=109643&view=auto
==============================================================================
--- llvm/trunk/test/Assembler/align-inst-load.ll (added)
+++ llvm/trunk/test/Assembler/align-inst-load.ll Wed Jul 28 15:12:04 2010
@@ -0,0 +1,6 @@
+; RUN: not llvm-as %s -o /dev/null 2>/dev/null
+
+define void @foo() {
+  load i1* %p, align 1073741824
+  ret void
+}

Added: llvm/trunk/test/Assembler/align-inst-store.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Assembler/align-inst-store.ll?rev=109643&view=auto
==============================================================================
--- llvm/trunk/test/Assembler/align-inst-store.ll (added)
+++ llvm/trunk/test/Assembler/align-inst-store.ll Wed Jul 28 15:12:04 2010
@@ -0,0 +1,6 @@
+; RUN: not llvm-as %s -o /dev/null 2>/dev/null
+
+define void @foo() {
+  store i1 false, i1* %p, align 1073741824
+  ret void
+}

Added: llvm/trunk/test/Assembler/align-inst.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Assembler/align-inst.ll?rev=109643&view=auto
==============================================================================
--- llvm/trunk/test/Assembler/align-inst.ll (added)
+++ llvm/trunk/test/Assembler/align-inst.ll Wed Jul 28 15:12:04 2010
@@ -0,0 +1,8 @@
+; RUN: llvm-as %s -o /dev/null
+
+define void @foo() {
+  %p = alloca i1, align 536870912
+  load i1* %p, align 536870912
+  store i1 false, i1* %p, align 536870912
+  ret void
+}