[AArch64AsmPrinter]Place jump tables into hot/unlikely-prefixed data sections for aarch64

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -893,9 +893,8 @@ class AsmPrinter : public MachineFunctionPass {
   // Internal Implementation Details
   //===------------------------------------------------------------------===//
 
-  void emitJumpTableImpl(const MachineJumpTableInfo &MJTI,
-                         ArrayRef<unsigned> JumpTableIndices,
-                         bool JTInDiffSection);
+  virtual void emitJumpTableImpl(const MachineJumpTableInfo &MJTI,
+                                 ArrayRef<unsigned> JumpTableIndices);
   void emitJumpTableEntry(const MachineJumpTableInfo &MJTI,
                           const MachineBasicBlock *MBB, unsigned uid) const;
 

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -2855,22 +2855,12 @@ void AsmPrinter::emitConstantPool() {
 void AsmPrinter::emitJumpTableInfo() {
   const MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
   if (!MJTI) return;
-  if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_Inline) return;
+
   const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
   if (JT.empty()) return;
 
-  // Pick the directive to use to print the jump table entries, and switch to
-  // the appropriate section.
-  const Function &F = MF->getFunction();
-  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
-  bool JTInDiffSection = !TLOF.shouldPutJumpTableInFunctionSection(
-      MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 ||
-          MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference64,
-      F);
-
   if (!TM.Options.EnableStaticDataPartitioning) {
-    emitJumpTableImpl(*MJTI, llvm::to_vector(llvm::seq<unsigned>(JT.size())),
-                      JTInDiffSection);
+    emitJumpTableImpl(*MJTI, llvm::to_vector(llvm::seq<unsigned>(JT.size())));
     return;
   }
 
@@ -2886,33 +2876,39 @@ void AsmPrinter::emitJumpTableInfo() {
     }
   }
 
-  emitJumpTableImpl(*MJTI, HotJumpTableIndices, JTInDiffSection);
-  emitJumpTableImpl(*MJTI, ColdJumpTableIndices, JTInDiffSection);
+  emitJumpTableImpl(*MJTI, HotJumpTableIndices);
+  emitJumpTableImpl(*MJTI, ColdJumpTableIndices);
 }
 
 void AsmPrinter::emitJumpTableImpl(const MachineJumpTableInfo &MJTI,
-                                   ArrayRef<unsigned> JumpTableIndices,
-                                   bool JTInDiffSection) {
-  if (JumpTableIndices.empty())
+                                   ArrayRef<unsigned> JumpTableIndices) {
+  if (MJTI.getEntryKind() == MachineJumpTableInfo::EK_Inline ||
+      JumpTableIndices.empty())
     return;
 
   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
   const Function &F = MF->getFunction();
   const std::vector<MachineJumpTableEntry> &JT = MJTI.getJumpTables();
   MCSection *JumpTableSection = nullptr;
-  if (TM.Options.EnableStaticDataPartitioning) {
-    JumpTableSection =
-        TLOF.getSectionForJumpTable(F, TM, &JT[JumpTableIndices.front()]);
-  } else {
-    JumpTableSection = TLOF.getSectionForJumpTable(F, TM);
-  }
 
-  const DataLayout &DL = MF->getDataLayout();
+  // Pick the directive to use to print the jump table entries, and switch to
+  // the appropriate section.
+  const bool JTInDiffSection = !TLOF.shouldPutJumpTableInFunctionSection(
+      MJTI.getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 ||
+          MJTI.getEntryKind() == MachineJumpTableInfo::EK_LabelDifference64,
+      F);
   if (JTInDiffSection) {
+    if (TM.Options.EnableStaticDataPartitioning) {
+      JumpTableSection =
+          TLOF.getSectionForJumpTable(F, TM, &JT[JumpTableIndices.front()]);
+    } else {
+      JumpTableSection = TLOF.getSectionForJumpTable(F, TM);
+    }
     OutStreamer->switchSection(JumpTableSection);
   }
 
-  emitAlignment(Align(MJTI.getEntryAlignment(MF->getDataLayout())));
+  const DataLayout &DL = MF->getDataLayout();
+  emitAlignment(Align(MJTI.getEntryAlignment(DL)));
 
   // Jump tables in code sections are marked with a data_region directive
   // where that's supported.

llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp

@@ -112,7 +112,8 @@ class AArch64AsmPrinter : public AsmPrinter {
   const MCExpr *lowerBlockAddressConstant(const BlockAddress &BA) override;
 
   void emitStartOfAsmFile(Module &M) override;
-  void emitJumpTableInfo() override;
+  void emitJumpTableImpl(const MachineJumpTableInfo &MJTI,
+                         ArrayRef<unsigned> JumpTableIndices) override;
   std::tuple<const MCSymbol *, uint64_t, const MCSymbol *,
              codeview::JumpTableEntrySize>
   getCodeViewJumpTableInfo(int JTI, const MachineInstr *BranchInstr,
@@ -1273,19 +1274,26 @@ void AArch64AsmPrinter::PrintDebugValueComment(const MachineInstr *MI,
   printOperand(MI, NOps - 2, OS);
 }
 
-void AArch64AsmPrinter::emitJumpTableInfo() {
-  const MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
-  if (!MJTI) return;
-
-  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
-  if (JT.empty()) return;
-
+void AArch64AsmPrinter::emitJumpTableImpl(const MachineJumpTableInfo &MJTI,
+                                          ArrayRef<unsigned> JumpTableIndices) {
+  // Fast return if there is nothing to emit to avoid creating empty sections.
+  if (JumpTableIndices.empty())
+    return;
   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
-  MCSection *ReadOnlySec = TLOF.getSectionForJumpTable(MF->getFunction(), TM);
+  const auto &F = MF->getFunction();
+  ArrayRef<MachineJumpTableEntry> JT = MJTI.getJumpTables();
+
+  MCSection *ReadOnlySec = nullptr;
+  if (TM.Options.EnableStaticDataPartitioning) {
+    ReadOnlySec =
+        TLOF.getSectionForJumpTable(F, TM, &JT[JumpTableIndices.front()]);
+  } else {
+    ReadOnlySec = TLOF.getSectionForJumpTable(F, TM);
+  }
   OutStreamer->switchSection(ReadOnlySec);
 
   auto AFI = MF->getInfo<AArch64FunctionInfo>();
-  for (unsigned JTI = 0, e = JT.size(); JTI != e; ++JTI) {
+  for (unsigned JTI : JumpTableIndices) {
     const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
 
     // If this jump table was deleted, ignore it.

llvm/test/CodeGen/AArch64/jump-table-partition.ll

@@ -0,0 +1,249 @@
+; The llc commands override two options
+; - 'aarch64-enable-atomic-cfg-tidy' to false to turn off simplifycfg pass,
+;    which can simplify away switch instructions before isel lowers switch instructions.
+; - 'aarch64-min-jump-table-entries' so 'switch' needs fewer cases to generate
+;    a jump table.
+
+; The static-data-splitter pass doesn't run.
+; RUN: llc -mtriple=aarch64-unknown-linux-gnu -function-sections=true \
+; RUN:     -aarch64-enable-atomic-cfg-tidy=false -aarch64-min-jump-table-entries=2 \
+; RUN:     -unique-section-names=true %s -o - 2>&1 | FileCheck %s --check-prefixes=DEFAULT
+
+; DEFAULT: .section .rodata.hot.foo,"a",@progbits
+; DEFAULT:   .LJTI0_0:
+; DEFAULT:   .LJTI0_1:
+; DEFAULT:   .LJTI0_2:
+; DEFAULT:   .LJTI0_3:
+; DEFAULT: .section .rodata.func_without_profile,"a",@progbits
+; DEFAULT:   .LJTI1_0:
+; DEFAULT: .section .rodata.bar_prefix.bar,"a",@progbits
+; DEFAULT: .LJTI2_0
+
+; RUN: llc -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions \
+; RUN:     -partition-static-data-sections=true -function-sections=true \
+; RUN:     -aarch64-enable-atomic-cfg-tidy=false -aarch64-min-jump-table-entries=2 \
+; RUN:     -unique-section-names=false %s -o - 2>&1 | FileCheck %s --check-prefixes=NUM,JT
+
+; Section names will optionally have `.<func>` if -function-sections is enabled.
+; RUN: llc -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions \
+; RUN:     -partition-static-data-sections=true -function-sections=true \
+; RUN:     -aarch64-enable-atomic-cfg-tidy=false -aarch64-min-jump-table-entries=2  \
+; RUN:     %s -o - 2>&1 | FileCheck %s --check-prefixes=FUNC,JT
+
+; RUN: llc -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions \
+; RUN:     -partition-static-data-sections=true -function-sections=false \
+; RUN:     -aarch64-enable-atomic-cfg-tidy=false -aarch64-min-jump-table-entries=2 \
+; RUN:     %s -o - 2>&1 | FileCheck %s --check-prefixes=FUNCLESS,JT
+
+; In function @foo, the 2 switch instructions to jt0.* and jt1.* are placed in
+; hot-prefixed sections, and the 2 switch instructions to jt2.* and jt3.* are
+; placed in cold-prefixed sections.
+; NUM:    .section .rodata.hot.,"a",@progbits,unique,2
+; FUNC:     .section .rodata.hot.foo,"a",@progbits
+; FUNCLESS: .section .rodata.hot.,"a",@progbits
+; JT: .LJTI0_0:
+; JT: .LJTI0_2:
+; NUM:        .section .rodata.unlikely.,"a",@progbits,unique,3
+; FUNC:       .section .rodata.unlikely.foo,
+; FUNCLESS:   .section .rodata.unlikely.,"a",@progbits
+; JT: .LJTI0_1:
+; JT: .LJTI0_3:
+
+; func_without_profile doesn't have profiles, so its jumptable doesn't have
+; hotness-based prefix.
+; NUM:        .section .rodata,"a",@progbits,unique,5
+; FUNC:       .section .rodata.func_without_profile,"a",@progbits
+; FUNCLESS:   .section .rodata,"a",@progbits
+; JT: .LJTI1_0:
+
+; @bar doesn't have profile information and it has a section prefix.
+; Tests that its jump tables are placed in sections with function prefixes.
+; NUM:        .section .rodata.bar_prefix.,"a",@progbits,unique,7
+; FUNC:       .section .rodata.bar_prefix.bar
+; FUNCLESS:   .section .rodata.bar_prefix.,"a"
+; JT: .LJTI2_0
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
+
+@str.9 = private constant [7 x i8] c".str.9\00"
+@str.10 = private constant [8 x i8] c".str.10\00"
+@str.11 = private constant [8 x i8] c".str.11\00"
+
+@case2 = private constant [7 x i8] c"case 2\00"
+@case1 = private constant [7 x i8] c"case 1\00"
+@default = private constant [8 x i8] c"default\00"
+@jt3 = private constant [4 x i8] c"jt3\00"
+
+; jt0 and jt2 are hot. jt1 and jt3 are cold.
+define i32 @foo(i32 %num) !prof !13 {
+entry:
+  %mod3 = sdiv i32 %num, 3
+  switch i32 %mod3, label %jt0.default [
+    i32 1, label %jt0.bb1
+    i32 2, label %jt0.bb2
+  ], !prof !14
+
+jt0.bb1:
+  call i32 @puts(ptr @case1)
+  br label %jt0.epilog
+
+jt0.bb2:
+  call i32 @puts(ptr @case2)
+  br label %jt0.epilog
+
+jt0.default:
+  call i32 @puts(ptr @default)
+  br label %jt0.epilog
+
+jt0.epilog:
+  %zero = icmp eq i32 %num, 0
+  br i1 %zero, label %hot, label %cold, !prof !17
+
+hot:
+ %c2 = call i32 @transform(i32 %num)
+  switch i32 %c2, label %jt2.default [
+    i32 1, label %jt2.bb1
+    i32 2, label %jt2.bb2
+  ], !prof !14
+
+jt2.bb1:
+  call i32 @puts(ptr @case1)
+  br label %jt1.epilog
+
+jt2.bb2:
+  call i32 @puts(ptr @case2)
+  br label %jt1.epilog
+
+jt2.default:
+  call i32 @puts(ptr @default)
+  br label %jt2.epilog
+
+jt2.epilog:
+  %c2cmp = icmp ne i32 %c2, 0
+  br i1 %c2cmp, label %return, label %jt3.prologue, !prof !18
+
+cold:
+  %c1 = call i32 @compute(i32 %num)
+  switch i32 %c1, label %jt1.default [
+    i32 1, label %jt1.bb1
+    i32 2, label %jt1.bb2
+  ], !prof !14
+
+jt1.bb1:
+  call i32 @puts(ptr @case1)
+  br label %jt1.epilog
+
+jt1.bb2:
+  call i32 @puts(ptr @case2)
+  br label %jt1.epilog
+
+jt1.default:
+  call i32 @puts(ptr @default)
+  br label %jt1.epilog
+
+jt1.epilog:
+  br label %return
+
+jt3.prologue:
+  %c3 = call i32 @cleanup(i32 %num)
+  switch i32 %c3, label %jt3.default [
+    i32 1, label %jt3.bb1
+    i32 2, label %jt3.bb2
+  ], !prof !14
+
+jt3.bb1:
+  call i32 @puts(ptr @case1)
+  br label %jt3.epilog
+
+jt3.bb2:
+  call i32 @puts(ptr @case2)
+  br label %jt3.epilog
+
+jt3.default:
+  call i32 @puts(ptr @default)
+  br label %jt3.epilog
+
+jt3.epilog:
+  call i32 @puts(ptr @jt3)
+  br label %return
+
+return:
+  ret i32 %mod3
+}
+
+define void @func_without_profile(i32 %num) {
+entry:
+  switch i32 %num, label %sw.default [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb:
+  call i32 @puts(ptr @str.10)
+  br label %sw.epilog
+
+sw.bb1: 
+  call i32 @puts(ptr @str.9)
+  br label %sw.epilog
+
+sw.default:
+  call i32 @puts(ptr @str.11)
+  br label %sw.epilog
+
+sw.epilog:                                       
+  ret void
+}
+
+define void @bar(i32 %num) !section_prefix !20  {
+entry:
+  switch i32 %num, label %sw.default [
+    i32 1, label %sw.bb
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb:
+  call i32 @puts(ptr @str.10)
+  br label %sw.epilog
+
+sw.bb1:
+  call i32 @puts(ptr @str.9)
+  br label %sw.epilog
+
+sw.default:
+  call i32 @puts(ptr @str.11)
+  br label %sw.epilog
+
+sw.epilog:
+  ret void
+}
+
+declare i32 @puts(ptr)
+declare i32 @printf(ptr, ...)
+declare i32 @compute(i32)
+declare i32 @transform(i32)
+declare i32 @cleanup(i32)
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"ProfileSummary", !1}
+!1 = !{!2, !3, !4, !5, !6, !7, !8, !9}
+!2 = !{!"ProfileFormat", !"InstrProf"}
+!3 = !{!"TotalCount", i64 230002}
+!4 = !{!"MaxCount", i64 100000}
+!5 = !{!"MaxInternalCount", i64 50000}
+!6 = !{!"MaxFunctionCount", i64 100000}
+!7 = !{!"NumCounts", i64 14}
+!8 = !{!"NumFunctions", i64 3}
+!9 = !{!"DetailedSummary", !10}
+!10 = !{!11, !12}
+!11 = !{i32 990000, i64 10000, i32 7}
+!12 = !{i32 999999, i64 1, i32 9}
+!13 = !{!"function_entry_count", i64 100000}
+!14 = !{!"branch_weights", i32 60000, i32 20000, i32 20000}
+!15 = !{!"function_entry_count", i64 1}
+!16 = !{!"branch_weights", i32 1, i32 0, i32 0, i32 0, i32 0, i32 0}
+!17 = !{!"branch_weights", i32 99999, i32 1}
+!18 = !{!"branch_weights", i32 99998, i32 1}
+!19 = !{!"branch_weights", i32 97000, i32 1000, i32 1000, i32 1000}
+!20 = !{!"function_section_prefix", !"bar_prefix"}