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CodeGen: Improve generated IR for __builtin_mul_overflow(uint, uint, int)
Add a special case for handling __builtin_mul_overflow with unsigned inputs and a signed output to avoid emitting the __muloti4 library call on x86_64. __muloti4 is not implemented in libgcc, so avoiding this call fixes compilation of some programs that call __builtin_mul_overflow with these arguments. For example, this fixes the build of cpio with clang, which includes code from gnulib that calls __builtin_mul_overflow with these argument types. Reviewed By: vsk Differential Revision: https://reviews.llvm.org/D84405
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2 files changed

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‎clang/lib/CodeGen/CGBuiltin.cpp

Lines changed: 47 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1832,6 +1832,47 @@ RValue CodeGenFunction::emitBuiltinOSLogFormat(const CallExpr &E) {
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return RValue::get(BufAddr.getPointer());
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}
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static bool isSpecialUnsignedMultiplySignedResult(
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unsigned BuiltinID, WidthAndSignedness Op1Info, WidthAndSignedness Op2Info,
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WidthAndSignedness ResultInfo) {
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return BuiltinID == Builtin::BI__builtin_mul_overflow &&
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Op1Info.Width == Op2Info.Width && Op2Info.Width == ResultInfo.Width &&
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!Op1Info.Signed && !Op2Info.Signed && ResultInfo.Signed;
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}
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static RValue EmitCheckedUnsignedMultiplySignedResult(
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CodeGenFunction &CGF, const clang::Expr *Op1, WidthAndSignedness Op1Info,
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const clang::Expr *Op2, WidthAndSignedness Op2Info,
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const clang::Expr *ResultArg, QualType ResultQTy,
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WidthAndSignedness ResultInfo) {
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assert(isSpecialUnsignedMultiplySignedResult(
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Builtin::BI__builtin_mul_overflow, Op1Info, Op2Info, ResultInfo) &&
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"Cannot specialize this multiply");
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llvm::Value *V1 = CGF.EmitScalarExpr(Op1);
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llvm::Value *V2 = CGF.EmitScalarExpr(Op2);
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llvm::Value *HasOverflow;
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llvm::Value *Result = EmitOverflowIntrinsic(
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CGF, llvm::Intrinsic::umul_with_overflow, V1, V2, HasOverflow);
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// The intrinsic call will detect overflow when the value is > UINT_MAX,
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// however, since the original builtin had a signed result, we need to report
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// an overflow when the result is greater than INT_MAX.
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auto IntMax = llvm::APInt::getSignedMaxValue(ResultInfo.Width);
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llvm::Value *IntMaxValue = llvm::ConstantInt::get(Result->getType(), IntMax);
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llvm::Value *IntMaxOverflow = CGF.Builder.CreateICmpUGT(Result, IntMaxValue);
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HasOverflow = CGF.Builder.CreateOr(HasOverflow, IntMaxOverflow);
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bool isVolatile =
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ResultArg->getType()->getPointeeType().isVolatileQualified();
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Address ResultPtr = CGF.EmitPointerWithAlignment(ResultArg);
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CGF.Builder.CreateStore(CGF.EmitToMemory(Result, ResultQTy), ResultPtr,
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isVolatile);
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return RValue::get(HasOverflow);
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}
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/// Determine if a binop is a checked mixed-sign multiply we can specialize.
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static bool isSpecialMixedSignMultiply(unsigned BuiltinID,
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WidthAndSignedness Op1Info,
@@ -3952,6 +3993,12 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
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RightInfo, ResultArg, ResultQTy,
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ResultInfo);
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if (isSpecialUnsignedMultiplySignedResult(BuiltinID, LeftInfo, RightInfo,
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ResultInfo))
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return EmitCheckedUnsignedMultiplySignedResult(
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*this, LeftArg, LeftInfo, RightArg, RightInfo, ResultArg, ResultQTy,
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ResultInfo);
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WidthAndSignedness EncompassingInfo =
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EncompassingIntegerType({LeftInfo, RightInfo, ResultInfo});
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‎clang/test/CodeGen/builtins-overflow.c

Lines changed: 48 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,9 @@
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// Test CodeGen for Security Check Overflow Builtins.
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// rdar://13421498
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4-
// RUN: %clang_cc1 -triple "i686-unknown-unknown" -emit-llvm -x c %s -o - | FileCheck %s
5-
// RUN: %clang_cc1 -triple "x86_64-unknown-unknown" -emit-llvm -x c %s -o - | FileCheck %s
6-
// RUN: %clang_cc1 -triple "x86_64-mingw32" -emit-llvm -x c %s -o - | FileCheck %s
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// RUN: %clang_cc1 -triple "i686-unknown-unknown" -emit-llvm -x c %s -o - | FileCheck -DLONG_TYPE=i32 -DLONG_MAX=2147483647 %s
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// RUN: %clang_cc1 -triple "x86_64-unknown-unknown" -emit-llvm -x c %s -o - | FileCheck -DLONG_TYPE=i64 -DLONG_MAX=9223372036854775807 %s
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// RUN: %clang_cc1 -triple "x86_64-mingw32" -emit-llvm -x c %s -o - | FileCheck -DLONG_TYPE=i32 -DLONG_MAX=2147483647 %s
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extern unsigned UnsignedErrorCode;
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extern unsigned long UnsignedLongErrorCode;
@@ -111,6 +111,51 @@ unsigned test_mul_overflow_uint_uint_uint(unsigned x, unsigned y) {
111111
return r;
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}
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int test_mul_overflow_uint_uint_int(unsigned x, unsigned y) {
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// CHECK-LABEL: define {{(dso_local )?}}i32 @test_mul_overflow_uint_uint_int
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// CHECK: [[S:%.+]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}})
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// CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0
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// CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1
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// CHECK: [[C1:%.+]] = icmp ugt i32 [[Q]], 2147483647
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// CHECK: [[C2:%.+]] = or i1 [[C]], [[C1]]
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// CHECK: store i32 [[Q]], i32*
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// CHECK: br i1 [[C2]]
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int r;
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if (__builtin_mul_overflow(x, y, &r))
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overflowed();
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return r;
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}
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int test_mul_overflow_uint_uint_int_volatile(unsigned x, unsigned y) {
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// CHECK-LABEL: define {{(dso_local )?}}i32 @test_mul_overflow_uint_uint_int_volatile
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// CHECK: [[S:%.+]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %{{.+}}, i32 %{{.+}})
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// CHECK-DAG: [[Q:%.+]] = extractvalue { i32, i1 } [[S]], 0
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// CHECK-DAG: [[C:%.+]] = extractvalue { i32, i1 } [[S]], 1
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// CHECK: [[C1:%.+]] = icmp ugt i32 [[Q]], 2147483647
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// CHECK: [[C2:%.+]] = or i1 [[C]], [[C1]]
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// CHECK: store volatile i32 [[Q]], i32*
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// CHECK: br i1 [[C2]]
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volatile int r;
139+
if (__builtin_mul_overflow(x, y, &r))
140+
overflowed();
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return r;
142+
}
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long test_mul_overflow_ulong_ulong_long(unsigned long x, unsigned long y) {
145+
// CHECK-LABEL: @test_mul_overflow_ulong_ulong_long
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// CHECK: [[S:%.+]] = call { [[LONG_TYPE]], i1 } @llvm.umul.with.overflow.[[LONG_TYPE]]([[LONG_TYPE]] %{{.+}}, [[LONG_TYPE]] %{{.+}})
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// CHECK-DAG: [[Q:%.+]] = extractvalue { [[LONG_TYPE]], i1 } [[S]], 0
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// CHECK-DAG: [[C:%.+]] = extractvalue { [[LONG_TYPE]], i1 } [[S]], 1
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// CHECK: [[C1:%.+]] = icmp ugt [[LONG_TYPE]] [[Q]], [[LONG_MAX]]
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// CHECK: [[C2:%.+]] = or i1 [[C]], [[C1]]
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// LONG64: store [[LONG_TYPE]] [[Q]], [[LONG_TYPE]]*
152+
// LONG64: br i1 [[C2]]
153+
long r;
154+
if (__builtin_mul_overflow(x, y, &r))
155+
overflowed();
156+
return r;
157+
}
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int test_mul_overflow_int_int_int(int x, int y) {
115160
// CHECK-LABEL: define {{(dso_local )?}}i32 @test_mul_overflow_int_int_int
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// CHECK-NOT: ext

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