forked from OSchip/llvm-project
[Analysis] Don't assume that unsigned overflow can't happen in EmitGEPOffset (PR42699)
Summary: Currently when computing a GEP offset using the function EmitGEPOffset for the following instruction getelementptr inbounds i32, i32* %p, i64 %offs we get mul nuw i64 %offs, 4 Unfortunately we cannot assume that unsigned wrapping won't happen here because %offs is allowed to be negative. Making such assumptions can lead to miscompilations: see the new test test24_neg_offs in InstCombine/icmp.ll. Without the patch InstCombine would generate the following comparison: icmp eq i64 %offs, 4611686018427387902; 0x3ffffffffffffffe Whereas the correct value to compare with is -2. This patch replaces the NUW flag with NSW in the multiplication instructions generated by EmitGEPOffset and adjusts the test suite. https://bugs.llvm.org/show_bug.cgi?id=42699 Reviewers: chandlerc, craig.topper, ostannard, lebedev.ri, spatel, efriedma, nlopes, aqjune Reviewed By: lebedev.ri Subscribers: reames, lebedev.ri, hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D68342 llvm-svn: 375089
This commit is contained in:
Mikhail Maltsev
parent
312c4a6e24
commit
b6534b2a26
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@ -32,7 +32,7 @@ Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
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Value *Result = Constant::getNullValue(IntPtrTy);
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// If the GEP is inbounds, we know that none of the addressing operations will
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// overflow in an unsigned sense.
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// overflow in a signed sense.
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bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
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// Build a mask for high order bits.
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@ -66,7 +66,8 @@ Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
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Constant *Scale = ConstantInt::get(IntPtrTy, Size);
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Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
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Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
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Scale =
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ConstantExpr::getMul(OC, Scale, false /*NUW*/, isInBounds /*NSW*/);
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// Emit an add instruction.
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Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
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continue;
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@ -82,7 +83,8 @@ Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
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if (Size != 1) {
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// We'll let instcombine(mul) convert this to a shl if possible.
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Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
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GEP->getName()+".idx", isInBounds /*NUW*/);
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GEP->getName() + ".idx", false /*NUW*/,
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isInBounds /*NSW*/);
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}
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// Emit an add instruction.
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@ -101,7 +101,7 @@ define i1 @test5({ i32, i32 }* %x, { i32, i32 }* %y) {
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define <2 x i1> @test6(<2 x i32> %X, <2 x %S*> %P) nounwind {
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; CHECK-LABEL: @test6(
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i32> [[X:%.*]], <i32 1073741823, i32 1073741823>
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i32> %X, <i32 -1, i32 -1>
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; CHECK-NEXT: ret <2 x i1> [[C]]
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;
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%A = getelementptr inbounds %S, <2 x %S*> %P, <2 x i32> zeroinitializer, <2 x i32> <i32 1, i32 1>, <2 x i32> %X
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@ -113,7 +113,7 @@ define <2 x i1> @test6(<2 x i32> %X, <2 x %S*> %P) nounwind {
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; Same as above, but indices scalarized.
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define <2 x i1> @test6b(<2 x i32> %X, <2 x %S*> %P) nounwind {
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; CHECK-LABEL: @test6b(
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i32> [[X:%.*]], <i32 1073741823, i32 1073741823>
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i32> %X, <i32 -1, i32 -1>
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; CHECK-NEXT: ret <2 x i1> [[C]]
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;
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%A = getelementptr inbounds %S, <2 x %S*> %P, i32 0, i32 1, <2 x i32> %X
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@ -175,10 +175,9 @@ define i1 @test13(i64 %X, %S* %P) {
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; CHECK: %C = icmp eq i64 %X, -1
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}
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; This is a test of icmp + shl nuw in disguise - 4611... is 0x3fff...
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define <2 x i1> @test13_vector(<2 x i64> %X, <2 x %S*> %P) nounwind {
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; CHECK-LABEL: @test13_vector(
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i64> %X, <i64 4611686018427387903, i64 4611686018427387903>
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i64> %X, <i64 -1, i64 -1>
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; CHECK-NEXT: ret <2 x i1> [[C]]
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;
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%A = getelementptr inbounds %S, <2 x %S*> %P, <2 x i64> zeroinitializer, <2 x i32> <i32 1, i32 1>, <2 x i64> %X
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@ -187,11 +186,10 @@ define <2 x i1> @test13_vector(<2 x i64> %X, <2 x %S*> %P) nounwind {
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ret <2 x i1> %C
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}
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; This is a test of icmp + shl nuw in disguise - 4611... is 0x3fff...
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define <2 x i1> @test13_vector2(i64 %X, <2 x %S*> %P) nounwind {
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; CHECK-LABEL: @test13_vector2(
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; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 0
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; CHECK-NEXT: [[TMP1:%.*]] = shl nuw <2 x i64> [[DOTSPLATINSERT]], <i64 2, i64 undef>
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; CHECK-NEXT: [[TMP1:%.*]] = shl <2 x i64> [[DOTSPLATINSERT]], <i64 2, i64 undef>
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; CHECK-NEXT: [[A_IDX:%.*]] = shufflevector <2 x i64> [[TMP1]], <2 x i64> undef, <2 x i32> zeroinitializer
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i64> [[A_IDX]], <i64 -4, i64 -4>
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; CHECK-NEXT: ret <2 x i1> [[C]]
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@ -206,7 +204,7 @@ define <2 x i1> @test13_vector2(i64 %X, <2 x %S*> %P) nounwind {
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define <2 x i1> @test13_vector3(i64 %X, <2 x %S*> %P) nounwind {
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; CHECK-LABEL: @test13_vector3(
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; CHECK-NEXT: [[DOTSPLATINSERT:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 0
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; CHECK-NEXT: [[TMP1:%.*]] = shl nuw <2 x i64> [[DOTSPLATINSERT]], <i64 2, i64 undef>
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; CHECK-NEXT: [[TMP1:%.*]] = shl <2 x i64> [[DOTSPLATINSERT]], <i64 2, i64 undef>
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; CHECK-NEXT: [[A_IDX:%.*]] = shufflevector <2 x i64> [[TMP1]], <2 x i64> undef, <2 x i32> zeroinitializer
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i64> [[A_IDX]], <i64 4, i64 4>
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; CHECK-NEXT: ret <2 x i1> [[C]]
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@ -227,10 +225,9 @@ define i1 @test13_as1(i16 %X, %S addrspace(1)* %P) {
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ret i1 %C
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}
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; This is a test of icmp + shl nuw in disguise - 16383 is 0x3fff.
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define <2 x i1> @test13_vector_as1(<2 x i16> %X, <2 x %S addrspace(1)*> %P) {
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; CHECK-LABEL: @test13_vector_as1(
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i16> %X, <i16 16383, i16 16383>
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; CHECK-NEXT: [[C:%.*]] = icmp eq <2 x i16> %X, <i16 -1, i16 -1>
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; CHECK-NEXT: ret <2 x i1> [[C]]
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;
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%A = getelementptr inbounds %S, <2 x %S addrspace(1)*> %P, <2 x i16> <i16 0, i16 0>, <2 x i32> <i32 1, i32 1>, <2 x i16> %X
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@ -45,7 +45,7 @@ define i1 @test60(i8* %foo, i64 %i, i64 %j) {
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; CHECK-LABEL: @test60(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[I:%.*]] to i32
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; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i32
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i32 [[TMP1]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i32 [[TMP1]], 2
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; CHECK-NEXT: [[TMP3:%.*]] = icmp slt i32 [[GEP1_IDX]], [[TMP2]]
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; CHECK-NEXT: ret i1 [[TMP3]]
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;
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@ -61,7 +61,7 @@ define i1 @test60_as1(i8 addrspace(1)* %foo, i64 %i, i64 %j) {
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; CHECK-LABEL: @test60_as1(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[I:%.*]] to i16
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; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i16
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i16 [[TMP1]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[TMP1]], 2
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; CHECK-NEXT: [[TMP3:%.*]] = icmp slt i16 [[GEP1_IDX]], [[TMP2]]
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; CHECK-NEXT: ret i1 [[TMP3]]
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;
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@ -93,7 +93,7 @@ define i1 @test60_addrspacecast(i8* %foo, i64 %i, i64 %j) {
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define i1 @test60_addrspacecast_smaller(i8* %foo, i16 %i, i64 %j) {
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; CHECK-LABEL: @test60_addrspacecast_smaller(
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i16 [[I:%.*]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[I:%.*]], 2
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[J:%.*]] to i16
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; CHECK-NEXT: [[TMP2:%.*]] = icmp slt i16 [[GEP1_IDX]], [[TMP1]]
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; CHECK-NEXT: ret i1 [[TMP2]]
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@ -508,6 +508,21 @@ define i1 @test24(i64 %i) {
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ret i1 %cmp
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}
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; Note: offs can be negative, LLVM used to make an incorrect assumption that
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; unsigned overflow does not happen during offset computation
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define i1 @test24_neg_offs(i32* %p, i64 %offs) {
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; CHECK-LABEL: @test24_neg_offs(
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[OFFS:%.*]], -2
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%p1 = getelementptr inbounds i32, i32* %p, i64 %offs
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%conv1 = ptrtoint i32* %p to i64
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%conv2 = ptrtoint i32* %p1 to i64
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%delta = sub i64 %conv1, %conv2
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%cmp = icmp eq i64 %delta, 8
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ret i1 %cmp
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}
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@X_as1 = addrspace(1) global [1000 x i32] zeroinitializer
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define i1 @test24_as1(i64 %i) {
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@ -1122,7 +1137,7 @@ define i1 @test59_as1(i8 addrspace(1)* %foo) {
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define i1 @test60(i8* %foo, i64 %i, i64 %j) {
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; CHECK-LABEL: @test60(
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i64 [[I:%.*]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[I:%.*]], 2
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; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i64 [[GEP1_IDX]], [[J:%.*]]
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; CHECK-NEXT: ret i1 [[TMP1]]
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;
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@ -1138,7 +1153,7 @@ define i1 @test60_as1(i8 addrspace(1)* %foo, i64 %i, i64 %j) {
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; CHECK-LABEL: @test60_as1(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[I:%.*]] to i16
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; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i16
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i16 [[TMP1]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[TMP1]], 2
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; CHECK-NEXT: [[TMP3:%.*]] = icmp slt i16 [[GEP1_IDX]], [[TMP2]]
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; CHECK-NEXT: ret i1 [[TMP3]]
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;
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@ -1154,7 +1169,7 @@ define i1 @test60_as1(i8 addrspace(1)* %foo, i64 %i, i64 %j) {
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; bitcast. This uses the same sized addrspace.
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define i1 @test60_addrspacecast(i8* %foo, i64 %i, i64 %j) {
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; CHECK-LABEL: @test60_addrspacecast(
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i64 [[I:%.*]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[I:%.*]], 2
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; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i64 [[GEP1_IDX]], [[J:%.*]]
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; CHECK-NEXT: ret i1 [[TMP1]]
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;
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@ -1168,7 +1183,7 @@ define i1 @test60_addrspacecast(i8* %foo, i64 %i, i64 %j) {
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define i1 @test60_addrspacecast_smaller(i8* %foo, i16 %i, i64 %j) {
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; CHECK-LABEL: @test60_addrspacecast_smaller(
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i16 [[I:%.*]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[I:%.*]], 2
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[J:%.*]] to i16
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; CHECK-NEXT: [[TMP2:%.*]] = icmp slt i16 [[GEP1_IDX]], [[TMP1]]
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; CHECK-NEXT: ret i1 [[TMP2]]
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@ -494,7 +494,7 @@ define i16 @test24a_as1(i8 addrspace(1)* %P, i16 %A) {
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define i64 @test24b(i8* %P, i64 %A){
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; CHECK-LABEL: @test24b(
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; CHECK-NEXT: [[B_IDX:%.*]] = shl nuw i64 [[A:%.*]], 1
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; CHECK-NEXT: [[B_IDX:%.*]] = shl nsw i64 [[A:%.*]], 1
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; CHECK-NEXT: ret i64 [[B_IDX]]
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;
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%B = getelementptr inbounds [42 x i16], [42 x i16]* @Arr, i64 0, i64 %A
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@ -506,9 +506,9 @@ define i64 @test24b(i8* %P, i64 %A){
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define i64 @test25(i8* %P, i64 %A){
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; CHECK-LABEL: @test25(
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; CHECK-NEXT: [[B_IDX:%.*]] = shl nuw i64 [[A:%.*]], 1
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; CHECK-NEXT: [[TMP1:%.*]] = add i64 [[B_IDX]], -84
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; CHECK-NEXT: ret i64 [[TMP1]]
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; CHECK-NEXT: [[B_IDX:%.*]] = shl nsw i64 [[A:%.*]], 1
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; CHECK-NEXT: [[DIFF_NEG:%.*]] = add i64 [[B_IDX]], -84
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; CHECK-NEXT: ret i64 [[DIFF_NEG]]
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;
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%B = getelementptr inbounds [42 x i16], [42 x i16]* @Arr, i64 0, i64 %A
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%C = ptrtoint i16* %B to i64
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@ -521,9 +521,9 @@ define i64 @test25(i8* %P, i64 %A){
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define i16 @test25_as1(i8 addrspace(1)* %P, i64 %A) {
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; CHECK-LABEL: @test25_as1(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[A:%.*]] to i16
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; CHECK-NEXT: [[B_IDX:%.*]] = shl nuw i16 [[TMP1]], 1
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; CHECK-NEXT: [[TMP2:%.*]] = add i16 [[B_IDX]], -84
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; CHECK-NEXT: ret i16 [[TMP2]]
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; CHECK-NEXT: [[B_IDX:%.*]] = shl nsw i16 [[TMP1]], 1
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; CHECK-NEXT: [[DIFF_NEG:%.*]] = add i16 [[B_IDX]], -84
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; CHECK-NEXT: ret i16 [[DIFF_NEG]]
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;
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%B = getelementptr inbounds [42 x i16], [42 x i16] addrspace(1)* @Arr_as1, i64 0, i64 %A
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%C = ptrtoint i16 addrspace(1)* %B to i16
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@ -668,7 +668,7 @@ define i64 @test29(i8* %foo, i64 %i, i64 %j) {
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define i64 @test30(i8* %foo, i64 %i, i64 %j) {
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; CHECK-LABEL: @test30(
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i64 [[I:%.*]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[I:%.*]], 2
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; CHECK-NEXT: [[TMP1:%.*]] = sub i64 [[GEP1_IDX]], [[J:%.*]]
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; CHECK-NEXT: ret i64 [[TMP1]]
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;
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@ -683,7 +683,7 @@ define i64 @test30(i8* %foo, i64 %i, i64 %j) {
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define i16 @test30_as1(i8 addrspace(1)* %foo, i16 %i, i16 %j) {
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; CHECK-LABEL: @test30_as1(
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nuw i16 [[I:%.*]], 2
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; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[I:%.*]], 2
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; CHECK-NEXT: [[TMP1:%.*]] = sub i16 [[GEP1_IDX]], [[J:%.*]]
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; CHECK-NEXT: ret i16 [[TMP1]]
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;
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