[JITLink][AArch32] Implement Armv5 ldr-pc stubs and use them for all pre-v7 targets

llvm/include/llvm/ExecutionEngine/JITLink/aarch32.h

@@ -131,33 +131,28 @@ const char *getEdgeKindName(Edge::Kind K);
 /// Stubs are often called "veneers" in the official docs and online.
 ///
 enum class StubsFlavor {
-  Unsupported = 0,
+  Undefined = 0,
+  pre_v7,
   v7,
 };
 
 /// JITLink sub-arch configuration for Arm CPU models
 struct ArmConfig {
   bool J1J2BranchEncoding = false;
-  StubsFlavor Stubs = StubsFlavor::Unsupported;
+  StubsFlavor Stubs = StubsFlavor::Undefined;
   // In the long term, we might want a linker switch like --target1-rel
   bool Target1Rel = false;
 };
 
 /// Obtain the sub-arch configuration for a given Arm CPU model.
 inline ArmConfig getArmConfigForCPUArch(ARMBuildAttrs::CPUArch CPUArch) {
   ArmConfig ArmCfg;
-  switch (CPUArch) {
-  case ARMBuildAttrs::v7:
-  case ARMBuildAttrs::v8_A:
+  if (CPUArch == ARMBuildAttrs::v7 || CPUArch >= ARMBuildAttrs::v7E_M) {
     ArmCfg.J1J2BranchEncoding = true;
     ArmCfg.Stubs = StubsFlavor::v7;
-    break;
-  default:
-    DEBUG_WITH_TYPE("jitlink", {
-      dbgs() << "  Warning: ARM config not defined for CPU architecture "
-             << getCPUArchName(CPUArch) << " (" << CPUArch << ")\n";
-    });
-    break;
+  } else {
+    ArmCfg.J1J2BranchEncoding = false;
+    ArmCfg.Stubs = StubsFlavor::pre_v7;
   }
   return ArmCfg;
 }
@@ -341,6 +336,37 @@ class GOTBuilder : public TableManager<GOTBuilder> {
   Section *GOTSection = nullptr;
 };
 
+/// Stubs builder emits non-position-independent Arm stubs for pre-v7 CPUs.
+/// These architectures have no MovT/MovW instructions and don't support Thumb2.
+/// BL is the only Thumb instruction that can generate stubs and they can always
+/// be transformed into BLX.
+class StubsManager_prev7 : public TableManager<StubsManager_prev7> {
+public:
+  StubsManager_prev7() = default;
+
+  /// Name of the object file section that will contain all our stubs.
+  static StringRef getSectionName() {
+    return "__llvm_jitlink_aarch32_STUBS_prev7";
+  }
+
+  /// Implements link-graph traversal via visitExistingEdges()
+  bool visitEdge(LinkGraph &G, Block *B, Edge &E);
+
+  /// Create a Arm stub for pre-v7 CPUs
+  Symbol &createEntry(LinkGraph &G, Symbol &Target);
+
+private:
+  /// Get or create the object file section that will contain all our stubs
+  Section &getStubsSection(LinkGraph &G) {
+    if (!StubsSection)
+      StubsSection = &G.createSection(getSectionName(),
+                                      orc::MemProt::Read | orc::MemProt::Exec);
+    return *StubsSection;
+  }
+
+  Section *StubsSection = nullptr;
+};
+
 /// Stubs builder for v7 emits non-position-independent Arm and Thumb stubs.
 class StubsManager_v7 {
 public:

llvm/lib/ExecutionEngine/JITLink/ELF_aarch32.cpp

@@ -265,21 +265,8 @@ createLinkGraphFromELFObject_aarch32(MemoryBufferRef ObjectBuffer) {
   // Resolve our internal configuration for the target. If at some point the
   // CPUArch alone becomes too unprecise, we can find more details in the
   // Tag_CPU_arch_profile.
-  aarch32::ArmConfig ArmCfg;
-  using namespace ARMBuildAttrs;
-  auto Arch = static_cast<CPUArch>(ARM::getArchAttr(AK));
-  switch (Arch) {
-  case v7:
-  case v8_A:
-    ArmCfg = aarch32::getArmConfigForCPUArch(Arch);
-    assert(ArmCfg.Stubs != aarch32::StubsFlavor::Unsupported &&
-           "Provide a config for each supported CPU");
-    break;
-  default:
-    return make_error<JITLinkError>(
-        "Failed to build ELF link graph: Unsupported CPU arch " +
-        StringRef(aarch32::getCPUArchName(Arch)));
-  }
+  auto Arch = static_cast<ARMBuildAttrs::CPUArch>(ARM::getArchAttr(AK));
+  aarch32::ArmConfig ArmCfg = aarch32::getArmConfigForCPUArch(Arch);
 
   // Populate the link-graph.
   switch (TT.getArch()) {
@@ -324,11 +311,15 @@ void link_ELF_aarch32(std::unique_ptr<LinkGraph> G,
       PassCfg.PrePrunePasses.push_back(markAllSymbolsLive);
 
     switch (ArmCfg.Stubs) {
+    case aarch32::StubsFlavor::pre_v7:
+      PassCfg.PostPrunePasses.push_back(
+          buildTables_ELF_aarch32<aarch32::StubsManager_prev7>);
+      break;
     case aarch32::StubsFlavor::v7:
       PassCfg.PostPrunePasses.push_back(
           buildTables_ELF_aarch32<aarch32::StubsManager_v7>);
       break;
-    case aarch32::StubsFlavor::Unsupported:
+    case aarch32::StubsFlavor::Undefined:
       llvm_unreachable("Check before building graph");
     }
   }

llvm/lib/ExecutionEngine/JITLink/aarch32.cpp

@@ -725,6 +725,49 @@ bool GOTBuilder::visitEdge(LinkGraph &G, Block *B, Edge &E) {
   return true;
 }
 
+/// Create a new node in the link-graph for the given stub template.
+template <size_t Size>
+static Block &allocStub(LinkGraph &G, Section &S, const uint8_t (&Code)[Size]) {
+  constexpr uint64_t Alignment = 4;
+  ArrayRef<char> Template(reinterpret_cast<const char *>(Code), Size);
+  return G.createContentBlock(S, Template, orc::ExecutorAddr(), Alignment, 0);
+}
+
+const uint8_t Armv5LongLdrPc[] = {
+    0x04, 0xf0, 0x1f, 0xe5, // ldr pc, [pc,#-4] ; L1
+    0x00, 0x00, 0x00, 0x00, // L1: .word S
+};
+
+Symbol &StubsManager_prev7::createEntry(LinkGraph &G, Symbol &Target) {
+  Block &B = allocStub(G, getStubsSection(G), Armv5LongLdrPc);
+  B.addEdge(Data_Pointer32, 4, Target, 0);
+  return G.addAnonymousSymbol(B, 0, B.getSize(), true, false);
+}
+
+bool StubsManager_prev7::visitEdge(LinkGraph &G, Block *B, Edge &E) {
+  if (E.getTarget().isDefined())
+    return false;
+
+  switch (E.getKind()) {
+  case Arm_Call:
+  case Arm_Jump24: {
+    DEBUG_WITH_TYPE("jitlink", {
+      dbgs() << "  Fixing " << G.getEdgeKindName(E.getKind()) << " edge at "
+             << B->getFixupAddress(E) << " (" << B->getAddress() << " + "
+             << formatv("{0:x}", E.getOffset()) << ")\n";
+    });
+    E.setTarget(this->getEntryForTarget(G, E.getTarget()));
+    return true;
+  }
+  case Thumb_Call:
+  case Thumb_Jump24:
+    // BL is never out-of-range and can always be rewritten to BLX inline.
+    // B can not target an external.
+    break;
+  }
+  return false;
+}
+
 const uint8_t Armv7ABS[] = {
     0x00, 0xc0, 0x00, 0xe3, // movw r12, #0x0000     ; lower 16-bit
     0x00, 0xc0, 0x40, 0xe3, // movt r12, #0x0000     ; upper 16-bit
@@ -737,14 +780,6 @@ const uint8_t Thumbv7ABS[] = {
     0x60, 0x47              // bx   r12
 };
 
-/// Create a new node in the link-graph for the given stub template.
-template <size_t Size>
-static Block &allocStub(LinkGraph &G, Section &S, const uint8_t (&Code)[Size]) {
-  constexpr uint64_t Alignment = 4;
-  ArrayRef<char> Template(reinterpret_cast<const char *>(Code), Size);
-  return G.createContentBlock(S, Template, orc::ExecutorAddr(), Alignment, 0);
-}
-
 static Block &createStubThumbv7(LinkGraph &G, Section &S, Symbol &Target) {
   Block &B = allocStub(G, S, Thumbv7ABS);
   B.addEdge(Thumb_MovwAbsNC, 0, Target, 0);

llvm/test/ExecutionEngine/JITLink/AArch32/ELF_relocations_arm.s

@@ -1,8 +1,22 @@
-# RUN: llvm-mc -triple=armv7-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t.o %s
-# RUN: llvm-objdump -r %t.o | FileCheck --check-prefix=CHECK-TYPE %s
-# RUN: llvm-objdump --disassemble %t.o | FileCheck --check-prefix=CHECK-INSTR %s
+# Test pre-v7 Arm features
+#
+# RUN: llvm-mc -triple=armv4t-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_armv4t.o %s
+# RUN: llvm-objdump -r %t_armv4t.o | FileCheck --check-prefix=CHECK-TYPE %s
+# RUN: llvm-objdump --disassemble %t_armv4t.o | FileCheck --check-prefix=CHECK-INSTR %s
 # RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
-# RUN:              -slab-page-size 4096 -show-entry-es -check %s %t.o
+# RUN:              -slab-page-size 4096 -check %s %t_armv4t.o
+#
+# RUN: llvm-mc -triple=armv7-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_armv7.o %s
+# RUN: llvm-objdump -r %t_armv7.o | FileCheck --check-prefix=CHECK-TYPE %s
+# RUN: llvm-objdump --disassemble %t_armv7.o | FileCheck --check-prefix=CHECK-INSTR %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
+# RUN:              -slab-page-size 4096 -check %s %t_armv7.o
+#
+# RUN: llvm-mc -triple=armv9-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_armv9.o %s
+# RUN: llvm-objdump -r %t_armv9.o | FileCheck --check-prefix=CHECK-TYPE %s
+# RUN: llvm-objdump --disassemble %t_armv9.o | FileCheck --check-prefix=CHECK-INSTR %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
+# RUN:              -slab-page-size 4096 -check %s %t_armv9.o
 
 
 	.text
@@ -63,38 +77,6 @@ jump24_target:
 	bx	lr
 	.size	jump24_target,	.-jump24_target
 
-
-# CHECK-TYPE: {{[0-9a-f]+}} R_ARM_MOVW_ABS_NC data_symbol
-# CHECK-INSTR: 	0000001c <movw>:
-# CHECK-INSTR: 	      1c: e3000000     movw      r0, #0x0
-# jitlink-check: decode_operand(movw, 1) = (data_symbol&0x0000ffff)
-	.globl	movw
-	.type	movw,%function
-	.p2align	2
-movw:
-	movw r0, :lower16:data_symbol
-	.size	movw,	.-movw
-
-# CHECK-TYPE: {{[0-9a-f]+}} R_ARM_MOVT_ABS data_symbol
-# CHECK-INSTR: 	00000020 <movt>:
-# CHECK-INSTR: 	      20: e3400000     movt      r0, #0x0
-# We decode the operand with index 2, because movt generates one leading implicit
-# predicate operand that we have to skip in order to decode the data_symbol operand
-# jitlink-check: decode_operand(movt, 2) = (data_symbol&0xffff0000>>16)
-	.globl	movt
-	.type	movt,%function
-	.p2align	2
-movt:
-	movt r0, :upper16:data_symbol
-	.size	movt,	.-movt
-
-	.data
-	.global data_symbol
-data_symbol:
-	.long 1073741822
-
-	.text
-
 # Empty main function for jitlink to be happy
 	.globl	main
 	.type	main,%function

llvm/test/ExecutionEngine/JITLink/AArch32/ELF_relocations_armv7plus.s

@@ -0,0 +1,49 @@
+# Test v7 Arm features
+#
+# RUN: llvm-mc -triple=armv7-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_armv7.o %s
+# RUN: llvm-objdump -r %t_armv7.o | FileCheck --check-prefix=CHECK-TYPE %s
+# RUN: llvm-objdump --disassemble %t_armv7.o | FileCheck --check-prefix=CHECK-INSTR %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
+# RUN:              -slab-page-size 4096 -abs data_symbol=0x00001234 -check %s %t_armv7.o
+#
+# RUN: llvm-mc -triple=armv9-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_armv9.o %s
+# RUN: llvm-objdump -r %t_armv9.o | FileCheck --check-prefix=CHECK-TYPE %s
+# RUN: llvm-objdump --disassemble %t_armv9.o | FileCheck --check-prefix=CHECK-INSTR %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
+# RUN:              -slab-page-size 4096 -abs data_symbol=0x00001234 -check %s %t_armv9.o
+
+
+	.text
+	.syntax unified
+
+# CHECK-TYPE: {{[0-9a-f]+}} R_ARM_MOVW_ABS_NC data_symbol
+# CHECK-INSTR: <movw>:
+# CHECK-INSTR: e3000000 movw r0, #0x0
+# jitlink-check: decode_operand(movw, 1) = data_symbol[15:0]
+	.globl	movw
+	.type	movw,%function
+	.p2align	2
+movw:
+	movw r0, :lower16:data_symbol
+	.size	movw,	.-movw
+
+# CHECK-TYPE: {{[0-9a-f]+}} R_ARM_MOVT_ABS data_symbol
+# CHECK-INSTR: <movt>:
+# CHECK-INSTR: e3400000 movt r0, #0x0
+# We decode the operand with index 2, because movt generates one leading implicit
+# predicate operand that we have to skip in order to decode the data_symbol operand
+# jitlink-check: decode_operand(movt, 2) = data_symbol[31:16]
+	.globl	movt
+	.type	movt,%function
+	.p2align	2
+movt:
+	movt r0, :upper16:data_symbol
+	.size	movt,	.-movt
+
+# Empty main function for jitlink to be happy
+	.globl	main
+	.type	main,%function
+	.p2align	2
+main:
+	bx	lr
+	.size	main,	.-main

llvm/test/ExecutionEngine/JITLink/AArch32/ELF_relocations_data.s

@@ -1,4 +1,9 @@
-# RUN: rm -rf %t && mkdir -p %t/armv7 && mkdir -p %t/thumbv7
+# RUN: rm -rf %t && mkdir -p %t/armv6 && mkdir -p %t/armv7 && mkdir -p %t/thumbv7
+# RUN: llvm-mc -triple=armv6-none-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t/armv6/out.o %s
+# RUN: llvm-objdump -r %t/armv6/out.o | FileCheck --check-prefix=CHECK-TYPE %s
+# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb -slab-page-size 4096 \
+# RUN:              -abs target=0x76bbe88f -check %s %t/armv6/out.o
+
 # RUN: llvm-mc -triple=armv7-none-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t/armv7/out.o %s
 # RUN: llvm-objdump -r %t/armv7/out.o | FileCheck --check-prefix=CHECK-TYPE %s
 # RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb -slab-page-size 4096 \