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82d29b397b
It's not undefined behavior for an unsigned left shift to overflow (i.e. to shift bits out), but it has been the source of bugs and exploits in certain codebases in the past. As we do in other parts of UBSan, this patch adds a dynamic checker which acts beyond UBSan and checks other sources of errors. The option is enabled as part of -fsanitize=integer. The flag is named: -fsanitize=unsigned-shift-base This matches shift-base and shift-exponent flags. <rdar://problem/46129047> Differential Revision: https://reviews.llvm.org/D86000
29 lines
1.2 KiB
C
29 lines
1.2 KiB
C
// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsanitize=unsigned-shift-base,shift-exponent %s -emit-llvm -o - | FileCheck %s
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// CHECK-LABEL: lsh_overflow(
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unsigned lsh_overflow(unsigned a, unsigned b) {
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// CHECK: %[[RHS_INBOUNDS:.*]] = icmp ule i32 %[[RHS:.*]], 31
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// CHECK-NEXT: br i1 %[[RHS_INBOUNDS]], label %[[CHECK_BB:.*]], label %[[CONT_BB:.*]],
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// CHECK: [[CHECK_BB]]:
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// CHECK-NEXT: %[[SHIFTED_OUT_WIDTH:.*]] = sub nuw nsw i32 31, %[[RHS]]
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// CHECK-NEXT: %[[SHIFTED_OUT:.*]] = lshr i32 %[[LHS:.*]], %[[SHIFTED_OUT_WIDTH]]
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// CHECK-NEXT: %[[SHIFTED_OUT_NOT_SIGN:.*]] = lshr i32 %[[SHIFTED_OUT]], 1
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// CHECK-NEXT: %[[NO_OVERFLOW:.*]] = icmp eq i32 %[[SHIFTED_OUT_NOT_SIGN]], 0
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// CHECK-NEXT: br label %[[CONT_BB]]
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// CHECK: [[CONT_BB]]:
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// CHECK-NEXT: %[[VALID_BASE:.*]] = phi i1 [ true, {{.*}} ], [ %[[NO_OVERFLOW]], %[[CHECK_BB]] ]
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// CHECK-NEXT: %[[VALID:.*]] = and i1 %[[RHS_INBOUNDS]], %[[VALID_BASE]]
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// CHECK-NEXT: br i1 %[[VALID]]
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// CHECK: call void @__ubsan_handle_shift_out_of_bounds
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// CHECK-NOT: call void @__ubsan_handle_shift_out_of_bounds
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// CHECK: %[[RET:.*]] = shl i32 %[[LHS]], %[[RHS]]
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// CHECK-NEXT: ret i32 %[[RET]]
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return a << b;
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}
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