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1711996805
In the LLVM middle-end we want to fold `gep inbounds null, idx -> null`: https://alive2.llvm.org/ce/z/5ZkPx- This pattern is common in real-world programs (https://github.com/dtcxzyw/llvm-opt-benchmark/pull/55#issuecomment-1870963906). Generally, it exists in some (actually) unreachable blocks, which is introduced by JumpThreading. However, some old-style offsetof macros are still widely used in real-world C/C++ code (e.g., hwloc/slurm/luajit). To avoid breaking existing code and inconvenience to downstream users, this patch removes the inbounds flag from the struct gep if the base pointer is null.
37 lines
1.1 KiB
C
37 lines
1.1 KiB
C
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
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// RUN: %clang_cc1 -x c -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
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// RUN: %clang_cc1 -x c -fsanitize=pointer-overflow -fno-sanitize-recover=pointer-overflow -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
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// RUN: %clang_cc1 -x c++ -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
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// RUN: %clang_cc1 -x c++ -fsanitize=pointer-overflow -fno-sanitize-recover=pointer-overflow -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct S {
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int x, y;
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};
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// CHECK-LABEL: @get_offset_of_y_naively(
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// CHECK-NEXT: entry:
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// CHECK-NEXT: ret i64 ptrtoint (ptr getelementptr ([[STRUCT_S:%.*]], ptr null, i32 0, i32 1) to i64)
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//
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uintptr_t get_offset_of_y_naively(void) {
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return ((uintptr_t)(&(((struct S *)0)->y)));
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}
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// CHECK-LABEL: @get_offset_of_y_via_builtin(
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// CHECK-NEXT: entry:
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// CHECK-NEXT: ret i64 4
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//
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uintptr_t get_offset_of_y_via_builtin(void) {
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return __builtin_offsetof(struct S, y);
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}
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#ifdef __cplusplus
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}
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#endif
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