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[LazyCallGraph] Skip blockaddresses
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blockaddresses do not participate in the call graph since the only
instructions that use them must all return to someplace within the
current function. And passes cannot retrieve a function address from a
blockaddress.

This was suggested by efriedma in D58260.

Fixes PR50881.

Reviewed By: nickdesaulniers

Differential Revision: https://reviews.llvm.org/D112178
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@aeubanks
aeubanks committed Nov 1, 2021
1 parent a82a844 commit 029f1a5
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Showing 5 changed files with 61 additions and 64 deletions.
24 changes: 3 additions & 21 deletions llvm/lib/Analysis/LazyCallGraph.cpp
View file
Expand Up @@ -1973,28 +1973,10 @@ void LazyCallGraph::visitReferences(SmallVectorImpl<Constant *> &Worklist,
continue;
}

// The blockaddress constant expression is a weird special case, we can't
// generically walk its operands the way we do for all other constants.
if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
// If we've already visited the function referred to by the block
// address, we don't need to revisit it.
if (Visited.count(BA->getFunction()))
continue;

// If all of the blockaddress' users are instructions within the
// referred to function, we don't need to insert a cycle.
if (llvm::all_of(BA->users(), [&](User *U) {
if (Instruction *I = dyn_cast<Instruction>(U))
return I->getFunction() == BA->getFunction();
return false;
}))
continue;

// Otherwise we should go visit the referred to function.
Visited.insert(BA->getFunction());
Worklist.push_back(BA->getFunction());
// blockaddresses are weird and don't participate in the call graph anyway,
// skip them.
if (isa<BlockAddress>(C))
continue;
}

for (Value *Op : C->operand_values())
if (Visited.insert(cast<Constant>(Op)).second)
Expand Down
28 changes: 28 additions & 0 deletions llvm/test/Analysis/LazyCallGraph/blockaddress.ll
View file
@@ -0,0 +1,28 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -passes="cgscc(function(sccp,simplifycfg))" < %s -S | FileCheck %s

define i32 @baz(i32 %y, i1 %b) {
; CHECK-LABEL: @baz(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[B:%.*]], label [[LAB:%.*]], label [[FOR_COND:%.*]]
; CHECK: for.cond:
; CHECK-NEXT: [[P_0:%.*]] = phi i8* [ null, [[FOR_COND]] ], [ blockaddress(@baz, [[LAB]]), [[ENTRY:%.*]] ]
; CHECK-NEXT: [[INCDEC_PTR:%.*]] = getelementptr inbounds i8, i8* [[P_0]], i64 1
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: lab:
; CHECK-NEXT: ret i32 0
;
entry:
br i1 %b, label %lab, label %for.cond.preheader

for.cond.preheader:
br label %for.cond

for.cond:
%p.0 = phi i8* [ null, %for.cond ], [ blockaddress(@baz, %lab), %for.cond.preheader ]
%incdec.ptr = getelementptr inbounds i8, i8* %p.0, i64 1
br label %for.cond

lab:
ret i32 0
}
58 changes: 20 additions & 38 deletions llvm/test/Transforms/Attributor/IPConstantProp/dangling-block-address.ll
View file
Expand Up @@ -34,37 +34,23 @@ entry:
}

define internal void @bar(i32* nocapture %pc) nounwind readonly {
; IS__CGSCC_OPM: Function Attrs: nounwind readonly
; IS__CGSCC_OPM-LABEL: define {{[^@]+}}@bar
; IS__CGSCC_OPM-SAME: (i32* nocapture [[PC:%.*]]) #[[ATTR1:[0-9]+]] {
; IS__CGSCC_OPM-NEXT: entry:
; IS__CGSCC_OPM-NEXT: br label [[INDIRECTGOTO:%.*]]
; IS__CGSCC_OPM: lab0:
; IS__CGSCC_OPM-NEXT: [[INDVAR_NEXT:%.*]] = add i32 [[INDVAR:%.*]], 1
; IS__CGSCC_OPM-NEXT: br label [[INDIRECTGOTO]]
; IS__CGSCC_OPM: end:
; IS__CGSCC_OPM-NEXT: ret void
; IS__CGSCC_OPM: indirectgoto:
; IS__CGSCC_OPM-NEXT: [[INDVAR]] = phi i32 [ [[INDVAR_NEXT]], [[LAB0:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; IS__CGSCC_OPM-NEXT: [[PC_ADDR_0:%.*]] = getelementptr i32, i32* [[PC]], i32 [[INDVAR]]
; IS__CGSCC_OPM-NEXT: [[TMP1_PN:%.*]] = load i32, i32* [[PC_ADDR_0]], align 4
; IS__CGSCC_OPM-NEXT: [[INDIRECT_GOTO_DEST_IN:%.*]] = getelementptr inbounds [2 x i8*], [2 x i8*]* @bar.l, i32 0, i32 [[TMP1_PN]]
; IS__CGSCC_OPM-NEXT: [[INDIRECT_GOTO_DEST:%.*]] = load i8*, i8** [[INDIRECT_GOTO_DEST_IN]], align 8
; IS__CGSCC_OPM-NEXT: indirectbr i8* [[INDIRECT_GOTO_DEST]], [label [[LAB0]], label %end]
;
; IS__CGSCC_NPM: Function Attrs: nofree norecurse nosync nounwind readnone
; IS__CGSCC_NPM-LABEL: define {{[^@]+}}@bar
; IS__CGSCC_NPM-SAME: () #[[ATTR1:[0-9]+]] {
; IS__CGSCC_NPM-NEXT: entry:
; IS__CGSCC_NPM-NEXT: br label [[INDIRECTGOTO:%.*]]
; IS__CGSCC_NPM: lab0:
; IS__CGSCC_NPM-NEXT: [[INDVAR_NEXT:%.*]] = add i32 [[INDVAR:%.*]], 1
; IS__CGSCC_NPM-NEXT: br label [[INDIRECTGOTO]]
; IS__CGSCC_NPM: end:
; IS__CGSCC_NPM-NEXT: ret void
; IS__CGSCC_NPM: indirectgoto:
; IS__CGSCC_NPM-NEXT: [[INDVAR]] = phi i32 [ [[INDVAR_NEXT]], [[LAB0:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; IS__CGSCC_NPM-NEXT: indirectbr i8* undef, [label [[LAB0]], label %end]
; IS__CGSCC____: Function Attrs: nounwind readonly
; IS__CGSCC____-LABEL: define {{[^@]+}}@bar
; IS__CGSCC____-SAME: (i32* nocapture [[PC:%.*]]) #[[ATTR1:[0-9]+]] {
; IS__CGSCC____-NEXT: entry:
; IS__CGSCC____-NEXT: br label [[INDIRECTGOTO:%.*]]
; IS__CGSCC____: lab0:
; IS__CGSCC____-NEXT: [[INDVAR_NEXT:%.*]] = add i32 [[INDVAR:%.*]], 1
; IS__CGSCC____-NEXT: br label [[INDIRECTGOTO]]
; IS__CGSCC____: end:
; IS__CGSCC____-NEXT: ret void
; IS__CGSCC____: indirectgoto:
; IS__CGSCC____-NEXT: [[INDVAR]] = phi i32 [ [[INDVAR_NEXT]], [[LAB0:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; IS__CGSCC____-NEXT: [[PC_ADDR_0:%.*]] = getelementptr i32, i32* [[PC]], i32 [[INDVAR]]
; IS__CGSCC____-NEXT: [[TMP1_PN:%.*]] = load i32, i32* [[PC_ADDR_0]], align 4
; IS__CGSCC____-NEXT: [[INDIRECT_GOTO_DEST_IN:%.*]] = getelementptr inbounds [2 x i8*], [2 x i8*]* @bar.l, i32 0, i32 [[TMP1_PN]]
; IS__CGSCC____-NEXT: [[INDIRECT_GOTO_DEST:%.*]] = load i8*, i8** [[INDIRECT_GOTO_DEST_IN]], align 8
; IS__CGSCC____-NEXT: indirectbr i8* [[INDIRECT_GOTO_DEST]], [label [[LAB0]], label %end]
;
entry:
br label %indirectgoto
Expand Down Expand Up @@ -104,11 +90,7 @@ entry:
;.
; IS__TUNIT____: attributes #[[ATTR0]] = { nofree nosync nounwind readnone willreturn }
;.
; IS__CGSCC_OPM: attributes #[[ATTR0]] = { nounwind readnone }
; IS__CGSCC_OPM: attributes #[[ATTR1]] = { nounwind readonly }
; IS__CGSCC_OPM: attributes #[[ATTR2]] = { nofree norecurse nosync nounwind readnone willreturn }
;.
; IS__CGSCC_NPM: attributes #[[ATTR0]] = { nounwind readnone }
; IS__CGSCC_NPM: attributes #[[ATTR1]] = { nofree norecurse nosync nounwind readnone }
; IS__CGSCC_NPM: attributes #[[ATTR2]] = { nofree norecurse nosync nounwind readnone willreturn }
; IS__CGSCC____: attributes #[[ATTR0]] = { nounwind readnone }
; IS__CGSCC____: attributes #[[ATTR1]] = { nounwind readonly }
; IS__CGSCC____: attributes #[[ATTR2]] = { nofree norecurse nosync nounwind readnone willreturn }
;.
12 changes: 8 additions & 4 deletions llvm/test/Transforms/Attributor/liveness.ll
View file
Expand Up @@ -2432,9 +2432,9 @@ define internal void @dead_with_blockaddress_users(i32* nocapture %pc) nounwind
; IS__CGSCC_OPM-NEXT: [[INDIRECT_GOTO_DEST:%.*]] = load i8*, i8** [[INDIRECT_GOTO_DEST_IN]]
; IS__CGSCC_OPM-NEXT: indirectbr i8* [[INDIRECT_GOTO_DEST]], [label [[LAB0]], label %end]
;
; IS__CGSCC____: Function Attrs: nofree norecurse nosync nounwind readnone
; IS__CGSCC____: Function Attrs: nounwind readonly
; IS__CGSCC____-LABEL: define {{[^@]+}}@dead_with_blockaddress_users
; IS__CGSCC____-SAME: () #[[ATTR14:[0-9]+]] {
; IS__CGSCC____-SAME: (i32* nocapture [[PC:%.*]]) #[[ATTR14:[0-9]+]] {
; IS__CGSCC____-NEXT: entry:
; IS__CGSCC____-NEXT: br label [[INDIRECTGOTO:%.*]]
; IS__CGSCC____: lab0:
Expand All @@ -2444,7 +2444,11 @@ define internal void @dead_with_blockaddress_users(i32* nocapture %pc) nounwind
; IS__CGSCC____-NEXT: ret void
; IS__CGSCC____: indirectgoto:
; IS__CGSCC____-NEXT: [[INDVAR]] = phi i32 [ [[INDVAR_NEXT]], [[LAB0:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; IS__CGSCC____-NEXT: indirectbr i8* undef, [label [[LAB0]], label %end]
; IS__CGSCC____-NEXT: [[PC_ADDR_0:%.*]] = getelementptr i32, i32* [[PC]], i32 [[INDVAR]]
; IS__CGSCC____-NEXT: [[TMP1_PN:%.*]] = load i32, i32* [[PC_ADDR_0]], align 4
; IS__CGSCC____-NEXT: [[INDIRECT_GOTO_DEST_IN:%.*]] = getelementptr inbounds [2 x i8*], [2 x i8*]* @dead_with_blockaddress_users.l, i32 0, i32 [[TMP1_PN]]
; IS__CGSCC____-NEXT: [[INDIRECT_GOTO_DEST:%.*]] = load i8*, i8** [[INDIRECT_GOTO_DEST_IN]], align 8
; IS__CGSCC____-NEXT: indirectbr i8* [[INDIRECT_GOTO_DEST]], [label [[LAB0]], label %end]
;
entry:
br label %indirectgoto
Expand Down Expand Up @@ -2681,7 +2685,7 @@ declare void @llvm.lifetime.end.p0i8(i64 %0, i8* %1)
; IS__CGSCC____: attributes #[[ATTR11]] = { nofree norecurse noreturn nosync nounwind readnone }
; IS__CGSCC____: attributes #[[ATTR12]] = { nofree norecurse noreturn nosync nounwind readnone willreturn }
; IS__CGSCC____: attributes #[[ATTR13]] = { nofree nosync nounwind willreturn }
; IS__CGSCC____: attributes #[[ATTR14]] = { nofree norecurse nosync nounwind readnone }
; IS__CGSCC____: attributes #[[ATTR14]] = { nounwind readonly }
; IS__CGSCC____: attributes #[[ATTR15]] = { nofree nosync nounwind readnone willreturn }
; IS__CGSCC____: attributes #[[ATTR16:[0-9]+]] = { argmemonly nofree nosync nounwind willreturn }
; IS__CGSCC____: attributes #[[ATTR17]] = { nounwind willreturn }
Expand Down
3 changes: 2 additions & 1 deletion llvm/unittests/Analysis/LazyCallGraphTest.cpp
View file
Expand Up @@ -1978,7 +1978,8 @@ TEST(LazyCallGraphTest, HandleBlockAddress) {
LazyCallGraph::Node &G = *CG.lookup(lookupFunction(*M, "g"));
EXPECT_EQ(&FRC, CG.lookupRefSCC(F));
EXPECT_EQ(&GRC, CG.lookupRefSCC(G));
EXPECT_TRUE(GRC.isParentOf(FRC));
EXPECT_FALSE(GRC.isParentOf(FRC));
EXPECT_FALSE(FRC.isParentOf(GRC));
}

// Test that a blockaddress that refers to itself creates no new RefSCC
Expand Down

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