Author: vedantk Date: Fri Jan 27 17:02:44 2017 New Revision: 293343 URL: http://llvm.org/viewvc/llvm-project?rev=293343&view=rev Log: [ubsan] Sanity-check shift amounts before truncation (fixes PR27271)
Ubsan does not report UB shifts in some cases where the shift exponent needs to be truncated to match the type of the shift base. We perform a range check on the truncated shift amount, leading to false negatives. Fix the issue (PR27271) by performing the range check on the original shift amount. Differential Revision: https://reviews.llvm.org/D29234 Added: cfe/trunk/test/CodeGen/ubsan-shift.c Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=293343&r1=293342&r2=293343&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original) +++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Fri Jan 27 17:02:44 2017 @@ -2751,8 +2751,8 @@ Value *ScalarExprEmitter::EmitShl(const isa<llvm::IntegerType>(Ops.LHS->getType())) { CodeGenFunction::SanitizerScope SanScope(&CGF); SmallVector<std::pair<Value *, SanitizerMask>, 2> Checks; - llvm::Value *WidthMinusOne = GetWidthMinusOneValue(Ops.LHS, RHS); - llvm::Value *ValidExponent = Builder.CreateICmpULE(RHS, WidthMinusOne); + llvm::Value *WidthMinusOne = GetWidthMinusOneValue(Ops.LHS, Ops.RHS); + llvm::Value *ValidExponent = Builder.CreateICmpULE(Ops.RHS, WidthMinusOne); if (SanitizeExponent) { Checks.push_back( Added: cfe/trunk/test/CodeGen/ubsan-shift.c URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/ubsan-shift.c?rev=293343&view=auto ============================================================================== --- cfe/trunk/test/CodeGen/ubsan-shift.c (added) +++ cfe/trunk/test/CodeGen/ubsan-shift.c Fri Jan 27 17:02:44 2017 @@ -0,0 +1,29 @@ +// RUN: %clang_cc1 -triple=x86_64-apple-darwin -fsanitize=shift-exponent -emit-llvm %s -o - | FileCheck %s + +// CHECK-LABEL: define i32 @f1 +int f1(int c, int shamt) { +// CHECK: icmp ule i32 %{{.*}}, 31, !nosanitize +// CHECK: icmp ule i32 %{{.*}}, 31, !nosanitize + return 1 << (c << shamt); +} + +// CHECK-LABEL: define i32 @f2 +int f2(long c, int shamt) { +// CHECK: icmp ule i32 %{{.*}}, 63, !nosanitize +// CHECK: icmp ule i64 %{{.*}}, 31, !nosanitize + return 1 << (c << shamt); +} + +// CHECK-LABEL: define i32 @f3 +unsigned f3(unsigned c, int shamt) { +// CHECK: icmp ule i32 %{{.*}}, 31, !nosanitize +// CHECK: icmp ule i32 %{{.*}}, 31, !nosanitize + return 1U << (c << shamt); +} + +// CHECK-LABEL: define i32 @f4 +unsigned f4(unsigned long c, int shamt) { +// CHECK: icmp ule i32 %{{.*}}, 63, !nosanitize +// CHECK: icmp ule i64 %{{.*}}, 31, !nosanitize + return 1U << (c << shamt); +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits