[llvm] r319761 - [InstCombine] Don't crash on out of bounds shifts

[Igor Laevsky via llvm-commits]

Author: igor.laevsky
Date: Tue Dec  5 04:18:15 2017
New Revision: 319761

URL: http://llvm.org/viewvc/llvm-project?rev=319761&view=rev
Log:
[InstCombine] Don't crash on out of bounds shifts

Differential Revision: https://reviews.llvm.org/D40649


Added:
    llvm/trunk/test/Transforms/InstCombine/out-of-bounds-indexes.ll
Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=319761&r1=319760&r2=319761&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Dec  5 04:18:15 2017
@@ -548,7 +548,7 @@ static void computeKnownBitsFromAssume(c
                            m_BitCast(m_Specific(V))));
 
     CmpInst::Predicate Pred;
-    ConstantInt *C;
+    uint64_t C;
     // assume(v = a)
     if (match(Arg, m_c_ICmp(Pred, m_V, m_Value(A))) &&
         Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@@ -650,51 +650,55 @@ static void computeKnownBitsFromAssume(c
     } else if (match(Arg, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
                                    m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ &&
-               isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+               isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
+               C < BitWidth) {
       KnownBits RHSKnown(BitWidth);
       computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
       // For those bits in RHS that are known, we can propagate them to known
       // bits in V shifted to the right by C.
-      RHSKnown.Zero.lshrInPlace(C->getZExtValue());
+      RHSKnown.Zero.lshrInPlace(C);
       Known.Zero |= RHSKnown.Zero;
-      RHSKnown.One.lshrInPlace(C->getZExtValue());
+      RHSKnown.One.lshrInPlace(C);
       Known.One  |= RHSKnown.One;
     // assume(~(v << c) = a)
     } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
                                    m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ &&
-               isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+               isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
+               C < BitWidth) {
       KnownBits RHSKnown(BitWidth);
       computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
       // For those bits in RHS that are known, we can propagate them inverted
       // to known bits in V shifted to the right by C.
-      RHSKnown.One.lshrInPlace(C->getZExtValue());
+      RHSKnown.One.lshrInPlace(C);
       Known.Zero |= RHSKnown.One;
-      RHSKnown.Zero.lshrInPlace(C->getZExtValue());
+      RHSKnown.Zero.lshrInPlace(C);
       Known.One  |= RHSKnown.Zero;
     // assume(v >> c = a)
     } else if (match(Arg,
                      m_c_ICmp(Pred, m_Shr(m_V, m_ConstantInt(C)),
                               m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ &&
-               isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+               isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
+               C < BitWidth) {
       KnownBits RHSKnown(BitWidth);
       computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
       // For those bits in RHS that are known, we can propagate them to known
       // bits in V shifted to the right by C.
-      Known.Zero |= RHSKnown.Zero << C->getZExtValue();
-      Known.One  |= RHSKnown.One  << C->getZExtValue();
+      Known.Zero |= RHSKnown.Zero << C;
+      Known.One  |= RHSKnown.One  << C;
     // assume(~(v >> c) = a)
     } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shr(m_V, m_ConstantInt(C))),
                                    m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ &&
-               isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+               isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
+               C < BitWidth) {
       KnownBits RHSKnown(BitWidth);
       computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
       // For those bits in RHS that are known, we can propagate them inverted
       // to known bits in V shifted to the right by C.
-      Known.Zero |= RHSKnown.One  << C->getZExtValue();
-      Known.One  |= RHSKnown.Zero << C->getZExtValue();
+      Known.Zero |= RHSKnown.One  << C;
+      Known.One  |= RHSKnown.Zero << C;
     // assume(v >=_s c) where c is non-negative
     } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_SGE &&

Added: llvm/trunk/test/Transforms/InstCombine/out-of-bounds-indexes.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/out-of-bounds-indexes.ll?rev=319761&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/out-of-bounds-indexes.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/out-of-bounds-indexes.ll Tue Dec  5 04:18:15 2017
@@ -0,0 +1,33 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; Check that we don't crash on unreasonable constant indexes
+
+define i32 @test_out_of_bounds(i32 %a, i1 %x, i1 %y) {
+; CHECK-LABEL: @test_out_of_bounds(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[A:%.*]], 3
+; CHECK-NEXT:    tail call void @llvm.assume(i1 false)
+; CHECK-NEXT:    ret i32 [[AND1]]
+;
+entry:
+  %and1 = and i32 %a, 3
+  %B = lshr i32 %and1, -2147483648
+  %cmp = icmp eq i32 %B, 1
+  tail call void @llvm.assume(i1 %cmp)
+  ret i32 %and1
+}
+
+define i128 @test_non64bit(i128 %a) {
+; CHECK-LABEL: @test_non64bit(
+; CHECK-NEXT:    [[AND1:%.*]] = and i128 [[A:%.*]], 3
+; CHECK-NEXT:    tail call void @llvm.assume(i1 false)
+; CHECK-NEXT:    ret i128 [[AND1]]
+;
+  %and1 = and i128 %a, 3
+  %B = lshr i128 %and1, -1
+  %cmp = icmp eq i128 %B, 1
+  tail call void @llvm.assume(i1 %cmp)
+  ret i128 %and1
+}
+
+declare void @llvm.assume(i1)