f0bbda00bd
Currenly both Clang and GCC support the following set of flags that control code gen of signed overflow: * -fwrapv: overflow is defined as in two-complement * -ftrapv: overflow traps * -fsanitize=signed-integer-overflow: if undefined (no -fwrapv), then overflow behaviour is controlled by UBSan runtime, overrides -ftrapv Howerver, clang ignores these flags for __builtin_abs(int) and its higher-width versions, so passing minimum integer value always causes poison. The same holds for *abs(), which are not handled in frontend at all but folded to llvm.abs.* intrinsics during InstCombinePass. The intrinsics are not instrumented by UBSan, so the functions need special handling as well. This patch does a few things: * Handle *abs() in CGBuiltin the same way as __builtin_*abs() * -fsanitize=signed-integer-overflow now properly instruments abs() with UBSan * -fwrapv and -ftrapv handling for abs() is made consistent with GCC Fixes #45129 and #45794 Reviewed By: efriedma, MaskRay Differential Revision: https://reviews.llvm.org/D156821
47 lines
2.2 KiB
C
47 lines
2.2 KiB
C
// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -o - -fwrapv -fsanitize=signed-integer-overflow | FileCheck %s --check-prefix=WRAPV
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -o - -ftrapv | FileCheck %s --check-prefixes=BOTH-TRAP,TRAPV
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -o - -fsanitize=signed-integer-overflow | FileCheck %s --check-prefixes=BOTH-TRAP,CATCH_UB
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// COM: TODO: Support -ftrapv-handler.
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extern int abs(int x);
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int absi(int x) {
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// WRAPV: [[NEG:%.*]] = sub i32 0, [[X:%.*]]
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// WRAPV: [[CMP:%.*]] = icmp slt i32 [[X]], 0
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// WRAPV: [[SEL:%.*]] = select i1 [[CMP]], i32 [[NEG]], i32 [[X]]
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//
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// BOTH-TRAP: [[NEG:%.*]] = call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 0, i32 [[X:%.*]])
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// BOTH-TRAP: [[NEGV:%.*]] = extractvalue { i32, i1 } [[NEG]], 0
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// BOTH-TRAP: [[OFL:%.*]] = extractvalue { i32, i1 } [[NEG]], 1
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// BOTH-TRAP: [[NOFL:%.*]] = xor i1 [[OFL]], true
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// BOTH-TRAP: br i1 [[NOFL]], label %[[CONT:.*]], label %[[TRAP:[a-zA-Z_.]*]]
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// BOTH-TRAP: [[TRAP]]:
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// TRAPV-NEXT: llvm.ubsantrap
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// CATCH_UB: @__ubsan_handle_negate_overflow
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// BOTH-TRAP-NEXT: unreachable
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// BOTH-TRAP: [[CONT]]:
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// BOTH-TRAP-NEXT: [[ABSCOND:%.*]] = icmp slt i32 [[X]], 0
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// BOTH-TRAP-NEXT: select i1 [[ABSCOND]], i32 [[NEGV]], i32 [[X]]
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return abs(x);
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}
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int babsi(int x) {
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// WRAPV: [[NEG:%.*]] = sub i32 0, [[X:%.*]]
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// WRAPV: [[CMP:%.*]] = icmp slt i32 [[X]], 0
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// WRAPV: [[SEL:%.*]] = select i1 [[CMP]], i32 [[NEG]], i32 [[X]]
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//
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// BOTH-TRAP: [[NEG:%.*]] = call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 0, i32 [[X:%.*]])
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// BOTH-TRAP: [[NEGV:%.*]] = extractvalue { i32, i1 } [[NEG]], 0
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// BOTH-TRAP: [[OFL:%.*]] = extractvalue { i32, i1 } [[NEG]], 1
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// BOTH-TRAP: [[NOFL:%.*]] = xor i1 [[OFL]], true
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// BOTH-TRAP: br i1 [[NOFL]], label %[[CONT:.*]], label %[[TRAP:[a-zA-Z_.]*]]
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// BOTH-TRAP: [[TRAP]]:
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// TRAPV-NEXT: llvm.ubsantrap
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// CATCH_UB: @__ubsan_handle_negate_overflow
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// BOTH-TRAP-NEXT: unreachable
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// BOTH-TRAP: [[CONT]]:
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// BOTH-TRAP-NEXT: [[ABSCOND:%.*]] = icmp slt i32 [[X]], 0
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// BOTH-TRAP-NEXT: select i1 [[ABSCOND]], i32 [[NEGV]], i32 [[X]]
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return __builtin_abs(x);
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}
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