llvmbot wrote:
@llvm/pr-subscribers-bolt
Author: Amir Ayupov (aaupov)
Changes
Deleted basic blocks are required for correct mapping of branches
modified by SCTC.
Test Plan: updated bb-with-two-tail-calls.s
---
Full diff: https://github.com/llvm/llvm-project/pull/91906.diff
4 Files Affected:
- (modified) bolt/docs/BAT.md (+5)
- (modified) bolt/include/bolt/Profile/BoltAddressTranslation.h (+1)
- (modified) bolt/lib/Profile/BoltAddressTranslation.cpp (+13)
- (modified) bolt/test/X86/bb-with-two-tail-calls.s (+9)
``diff
diff --git a/bolt/docs/BAT.md b/bolt/docs/BAT.md
index 7ffb5d7c00816..817ad288aa34b 100644
--- a/bolt/docs/BAT.md
+++ b/bolt/docs/BAT.md
@@ -106,9 +106,14 @@ equals output offset.
`BRANCHENTRY` bit denotes whether a given offset pair is a control flow source
(branch or call instruction). If not set, it signifies a control flow target
(basic block offset).
+
`InputAddr` is omitted for equal offsets in input and output function. In this
case, `BRANCHENTRY` bits are encoded separately in a `BranchEntries` bitvector.
+Deleted basic blocks are emitted as having `OutputOffset` equal to the size of
+the function. They don't affect address translation and only participate in
+input basic block mapping.
+
### Secondary Entry Points table
The table is emitted for hot fragments only. It contains `NumSecEntryPoints`
offsets denoting secondary entry points, delta encoded, implicitly starting at
zero.
diff --git a/bolt/include/bolt/Profile/BoltAddressTranslation.h
b/bolt/include/bolt/Profile/BoltAddressTranslation.h
index 68b993ee363cc..16fe0442f10a5 100644
--- a/bolt/include/bolt/Profile/BoltAddressTranslation.h
+++ b/bolt/include/bolt/Profile/BoltAddressTranslation.h
@@ -217,6 +217,7 @@ class BoltAddressTranslation {
auto begin() const { return Map.begin(); }
auto end() const { return Map.end(); }
auto upper_bound(uint32_t Offset) const { return Map.upper_bound(Offset); }
+auto size() const { return Map.size(); }
};
/// Map function output address to its hash and basic blocks hash map.
diff --git a/bolt/lib/Profile/BoltAddressTranslation.cpp
b/bolt/lib/Profile/BoltAddressTranslation.cpp
index 7cfb9c132c2c6..724b348c7845e 100644
--- a/bolt/lib/Profile/BoltAddressTranslation.cpp
+++ b/bolt/lib/Profile/BoltAddressTranslation.cpp
@@ -108,6 +108,19 @@ void BoltAddressTranslation::write(const BinaryContext
, raw_ostream ) {
for (const BinaryBasicBlock *const BB :
Function.getLayout().getMainFragment())
writeEntriesForBB(Map, *BB, InputAddress, OutputAddress);
+// Add entries for deleted blocks. They are still required for correct BB
+// mapping of branches modified by SCTC. By convention, they would have the
+// end of the function as output address.
+const BBHashMapTy = getBBHashMap(InputAddress);
+if (BBHashMap.size() != Function.size()) {
+ const uint64_t EndOffset = Function.getOutputSize();
+ std::unordered_set MappedInputOffsets;
+ for (const BinaryBasicBlock : Function)
+MappedInputOffsets.emplace(BB.getInputOffset());
+ for (const auto &[InputOffset, _] : BBHashMap)
+if (!llvm::is_contained(MappedInputOffsets, InputOffset))
+ Map[EndOffset] = InputOffset << 1;
+}
Maps.emplace(Function.getOutputAddress(), std::move(Map));
ReverseMap.emplace(OutputAddress, InputAddress);
diff --git a/bolt/test/X86/bb-with-two-tail-calls.s
b/bolt/test/X86/bb-with-two-tail-calls.s
index bb2b0cd4cc23a..c0b01e1894a49 100644
--- a/bolt/test/X86/bb-with-two-tail-calls.s
+++ b/bolt/test/X86/bb-with-two-tail-calls.s
@@ -10,11 +10,20 @@
# RUN: %clang %cflags %t.o -o %t.exe -Wl,-q -nostdlib
# RUN: llvm-bolt %t.exe -o %t.out --data %t.fdata --lite=0 --dyno-stats \
# RUN:--print-sctc --print-only=_start -enable-bat 2>&1 | FileCheck %s
+# RUN: llvm-objdump --syms %t.out | FileCheck %s --check-prefix=CHECK-NM
+# RUN: llvm-bat-dump %t.out --dump-all | FileCheck %s --check-prefix=CHECK-BAT
+
# 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
+# Confirm that a deleted basic block is emitted at function end offset (0xe)
+# CHECK-NM: 0060 g .text 000e _start
+# CHECK-BAT: Function Address: 0x60, hash: 0xf8bf620b266cdc1b
+# CHECK-BAT: 0xe -> 0xc hash: 0x823623240f000c
+# CHECK-BAT: NumBlocks: 5
+
.globl _start
_start:
je x
``
https://github.com/llvm/llvm-project/pull/91906
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