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[BOLT] Fix preserved offset in fixDoubleJumps #92485

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Merged
merged 1 commit into from
May 19, 2024
Merged

[BOLT] Fix preserved offset in fixDoubleJumps #92485

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14 changes: 9 additions & 5 deletions bolt/lib/Passes/BinaryPasses.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -674,7 +674,8 @@ static uint64_t fixDoubleJumps(BinaryFunction &Function, bool MarkInvalid) {
MCPlusBuilder *MIB = Function.getBinaryContext().MIB.get();
for (BinaryBasicBlock &BB : Function) {
auto checkAndPatch = [&](BinaryBasicBlock *Pred, BinaryBasicBlock *Succ,
const MCSymbol *SuccSym) {
const MCSymbol *SuccSym,
std::optional<uint32_t> Offset) {
// Ignore infinite loop jumps or fallthrough tail jumps.
if (Pred == Succ || Succ == &BB)
return false;
Expand Down Expand Up @@ -715,9 +716,11 @@ static uint64_t fixDoubleJumps(BinaryFunction &Function, bool MarkInvalid) {
Pred->removeSuccessor(&BB);
Pred->eraseInstruction(Pred->findInstruction(Branch));
Pred->addTailCallInstruction(SuccSym);
MCInst *TailCall = Pred->getLastNonPseudoInstr();
assert(TailCall);
MIB->setOffset(*TailCall, BB.getOffset());
if (Offset) {
MCInst *TailCall = Pred->getLastNonPseudoInstr();
assert(TailCall);
MIB->setOffset(*TailCall, *Offset);
}
} else {
return false;
}
Expand Down Expand Up @@ -760,7 +763,8 @@ static uint64_t fixDoubleJumps(BinaryFunction &Function, bool MarkInvalid) {
if (Pred->getSuccessor() == &BB ||
(Pred->getConditionalSuccessor(true) == &BB && !IsTailCall) ||
Pred->getConditionalSuccessor(false) == &BB)
if (checkAndPatch(Pred, Succ, SuccSym) && MarkInvalid)
if (checkAndPatch(Pred, Succ, SuccSym, MIB->getOffset(*Inst)) &&
MarkInvalid)
BB.markValid(BB.pred_size() != 0 || BB.isLandingPad() ||
BB.isEntryPoint());
}
Expand Down
8 changes: 4 additions & 4 deletions bolt/test/X86/bb-with-two-tail-calls.s
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Original file line number Diff line number Diff line change
@@ -1,8 +1,6 @@
# This reproduces a bug with dynostats when trying to compute branch stats
# at a block with two tails calls (one conditional and one unconditional).

# REQUIRES: system-linux

# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown \
# RUN: %s -o %t.o
# RUN: link_fdata %s %t.o %t.fdata
Expand All @@ -13,7 +11,7 @@
# CHECK-NOT: Assertion `BranchInfo.size() == 2 && "could only be called for blocks with 2 successors"' failed.
# Two tail calls in the same basic block after SCTC:
# CHECK: {{.*}}: ja {{.*}} # TAILCALL # Offset: 7 # CTCTakenCount: 4
# CHECK-NEXT: {{.*}}: jmp {{.*}} # TAILCALL # Offset: 12
# CHECK-NEXT: {{.*}}: jmp {{.*}} # TAILCALL # Offset: 13

.globl _start
_start:
Expand All @@ -23,7 +21,9 @@ a: ja b
x: ret
# FDATA: 1 _start #a# 1 _start #b# 2 4
b: jmp e
c: jmp f
c:
.nops 1
jmp f

.globl e
e:
Expand Down
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