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author | Benjamin Kramer <benny.kra@googlemail.com> | 2013-01-24 16:28:28 +0000 |
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committer | Benjamin Kramer <benny.kra@googlemail.com> | 2013-01-24 16:28:28 +0000 |
commit | e5742464895b7f1fcc6a5b968b72f6ec66a1fd44 (patch) | |
tree | 4813758eebc6458e266fe664c5f503d6db147546 | |
parent | 41d35a335efb30710c0ad806833379fe0373c7a0 (diff) | |
download | llvm-e5742464895b7f1fcc6a5b968b72f6ec66a1fd44.tar.gz llvm-e5742464895b7f1fcc6a5b968b72f6ec66a1fd44.tar.bz2 llvm-e5742464895b7f1fcc6a5b968b72f6ec66a1fd44.tar.xz |
ConstantFolding: Add a missing folding that leads to a miscompile.
We use constant folding to see if an intrinsic evaluates to the same value as a
constant that we know. If we don't take the undefinedness into account we get a
value that doesn't match the actual implementation, and miscompiled code.
This was uncovered by Chandler's simplifycfg changes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173356 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Analysis/ConstantFolding.cpp | 8 | ||||
-rw-r--r-- | test/Transforms/ConstProp/2007-11-23-cttz.ll | 2 | ||||
-rw-r--r-- | test/Transforms/InstCombine/intrinsics.ll | 36 |
3 files changed, 41 insertions, 5 deletions
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp index 9246e26422..4b4fa5cd4e 100644 --- a/lib/Analysis/ConstantFolding.cpp +++ b/lib/Analysis/ConstantFolding.cpp @@ -1474,12 +1474,12 @@ llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands, return ConstantStruct::get(cast<StructType>(F->getReturnType()), Ops); } case Intrinsic::cttz: - // FIXME: This should check for Op2 == 1, and become unreachable if - // Op1 == 0. + if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef. + return UndefValue::get(Ty); return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros()); case Intrinsic::ctlz: - // FIXME: This should check for Op2 == 1, and become unreachable if - // Op1 == 0. + if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef. + return UndefValue::get(Ty); return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros()); } } diff --git a/test/Transforms/ConstProp/2007-11-23-cttz.ll b/test/Transforms/ConstProp/2007-11-23-cttz.ll index 6d34cb17ff..c5ee70c2ff 100644 --- a/test/Transforms/ConstProp/2007-11-23-cttz.ll +++ b/test/Transforms/ConstProp/2007-11-23-cttz.ll @@ -3,6 +3,6 @@ declare i13 @llvm.cttz.i13(i13, i1) define i13 @test() { - %X = call i13 @llvm.cttz.i13(i13 0, i1 true) + %X = call i13 @llvm.cttz.i13(i13 0, i1 false) ret i13 %X } diff --git a/test/Transforms/InstCombine/intrinsics.ll b/test/Transforms/InstCombine/intrinsics.ll index 93f0a953fd..f334b3b1e9 100644 --- a/test/Transforms/InstCombine/intrinsics.ll +++ b/test/Transforms/InstCombine/intrinsics.ll @@ -220,3 +220,39 @@ define i32 @cttz_simplify1b(i32 %x) nounwind readnone ssp { ; CHECK: @cttz_simplify1b ; CHECK-NEXT: ret i32 0 } + +define i32 @ctlz_undef(i32 %Value) nounwind { + %ctlz = call i32 @llvm.ctlz.i32(i32 0, i1 true) + ret i32 %ctlz + +; CHECK: @ctlz_undef +; CHECK-NEXT: ret i32 undef +} + +define i32 @cttz_undef(i32 %Value) nounwind { + %cttz = call i32 @llvm.cttz.i32(i32 0, i1 true) + ret i32 %cttz + +; CHECK: @cttz_undef +; CHECK-NEXT: ret i32 undef +} + +define i32 @ctlz_select(i32 %Value) nounwind { + %tobool = icmp ne i32 %Value, 0 + %ctlz = call i32 @llvm.ctlz.i32(i32 %Value, i1 true) + %s = select i1 %tobool, i32 %ctlz, i32 32 + ret i32 %s + +; CHECK: @ctlz_select +; CHECK: select i1 %tobool, i32 %ctlz, i32 32 +} + +define i32 @cttz_select(i32 %Value) nounwind { + %tobool = icmp ne i32 %Value, 0 + %cttz = call i32 @llvm.cttz.i32(i32 %Value, i1 true) + %s = select i1 %tobool, i32 %cttz, i32 32 + ret i32 %s + +; CHECK: @cttz_select +; CHECK: select i1 %tobool, i32 %cttz, i32 32 +} |