[JITLink][PowerPC] Support R_PPC64_PCREL34

PC-relative instructions are added in ISA-3.1 implemented by pwr10. This patch adds basic pc-relative relocation. Reviewed By: lhames Differential Revision: https://reviews.llvm.org/D155771
llvm · Aug 2, 2023 · ca6d86f · ca6d86f
1 parent ed83797
commit ca6d86f
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diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/ppc64.h b/llvm/include/llvm/ExecutionEngine/JITLink/ppc64.h
@@ -24,6 +24,7 @@ enum EdgeKind_ppc64 : Edge::Kind {
   Pointer64 = Edge::FirstRelocation,
   Pointer32,
   Delta64,
+  Delta34,
   Delta32,
   NegDelta32,
   Delta16,
@@ -229,6 +230,26 @@ inline static uint16_t ha16(uint64_t x) { return (x + 0x8000) >> 16; }
 
 inline static uint16_t lo16(uint64_t x) { return x & 0xffff; }
 
+// Prefixed instruction introduced in ISAv3.1 consists of two 32-bit words,
+// prefix word and suffix word, i.e., prefixed_instruction = concat(prefix_word,
+// suffix_word). That's to say, for a prefixed instruction encoded in uint64_t,
+// the most significant 32 bits belong to the prefix word. The prefix word is at
+// low address for both big/little endian. Byte order in each word still follows
+// its endian.
+template <support::endianness Endianness>
+inline static uint64_t readPrefixedInstruction(const char *Loc) {
+  constexpr bool isLE = Endianness == support::endianness::little;
+  uint64_t Inst = support::endian::read64<Endianness>(Loc);
+  return isLE ? (Inst << 32) | (Inst >> 32) : Inst;
+}
+
+template <support::endianness Endianness>
+inline static void writePrefixedInstruction(char *Loc, uint64_t Inst) {
+  constexpr bool isLE = Endianness == support::endianness::little;
+  Inst = isLE ? (Inst << 32) | (Inst >> 32) : Inst;
+  support::endian::write64<Endianness>(Loc, Inst);
+}
+
 /// Apply fixup expression for edge to block content.
 template <support::endianness Endianness>
 inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
@@ -315,6 +336,18 @@ inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
     support::endian::write64<Endianness>(FixupPtr, Value);
     break;
   }
+  case Delta34: {
+    int64_t Value = S + A - P;
+    if (!LLVM_UNLIKELY(isInt<34>(Value)))
+      return makeTargetOutOfRangeError(G, B, E);
+    static const uint64_t SI0Mask = 0x00000003ffff0000;
+    static const uint64_t SI1Mask = 0x000000000000ffff;
+    static const uint64_t FullMask = 0x0003ffff0000ffff;
+    uint64_t Inst = readPrefixedInstruction<Endianness>(FixupPtr) & ~FullMask;
+    writePrefixedInstruction<Endianness>(
+        FixupPtr, Inst | ((Value & SI0Mask) << 16) | (Value & SI1Mask));
+    break;
+  }
   case Delta32: {
     int64_t Value = S + A - P;
     if (LLVM_UNLIKELY(!isInt<32>(Value))) {

diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_ppc64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_ppc64.cpp
@@ -228,6 +228,9 @@ class ELFLinkGraphBuilder_ppc64
     case ELF::R_PPC64_REL64:
       Kind = ppc64::Delta64;
       break;
+    case ELF::R_PPC64_PCREL34:
+      Kind = ppc64::Delta34;
+      break;
     }
 
     Edge GE(Kind, Offset, *GraphSymbol, Addend);

diff --git a/llvm/lib/ExecutionEngine/JITLink/ppc64.cpp b/llvm/lib/ExecutionEngine/JITLink/ppc64.cpp
@@ -66,6 +66,8 @@ const char *getEdgeKindName(Edge::Kind K) {
     return "Pointer32";
   case Delta64:
     return "Delta64";
+  case Delta34:
+    return "Delta34";
   case Delta32:
     return "Delta32";
   case NegDelta32:

diff --git a/llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64le_relocations.s b/llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64le_relocations.s
@@ -82,6 +82,23 @@ test_external_call_notoc:
   blr
   .size test_external_call_notoc, .-test_external_call_notoc
 
+# Check R_PPC64_PCREL34
+# jitlink-check: (section_addr(elf_reloc.o, .rodata.str1.1) - test_pcrel34)[33:0] = \
+# jitlink-check:   ((((*{4}(test_pcrel34)) & 0x3ffff) << 16) | ((*{4}(test_pcrel34 + 4)) & 0xffff))[33:0]
+  .global test_pcrel34
+  .p2align 4
+  .type test_pcrel34,@function
+test_pcrel34:
+  paddi 3, 0, .L.str@PCREL, 1
+  blr
+  .size test_pcrel34, .-test_pcrel34
+
+  .type	.L.str,@object
+	.section	.rodata.str1.1,"aMS",@progbits,1
+.L.str:
+	.asciz	"Hey!"
+	.size	.L.str, 5
+
  .section .toc,"aw",@progbits
 .LC0:
   .tc external_data[TC],external_data
diff --git a/llvm/test/ExecutionEngine/JITLink/ppc64/ppc64le-relocs.s b/llvm/test/ExecutionEngine/JITLink/ppc64/ppc64le-relocs.s
@@ -183,6 +183,17 @@ bar:
 .Lfunc_end7:
 	.size	bar, .Lfunc_end7-.Lfunc_begin7
 
+  .global foobar
+  .p2align
+  .type foobar,@function
+foobar:
+.Lfunc_begin8:
+  .localentry foobar, 1
+  paddi 3, 0, .L.str@PCREL, 1
+  blr
+.Lfunc_end8:
+  .size foobar, .Lfunc_end8-.Lfunc_end8
+
 	.type	local_var,@object
 	.section	.bss,"aw",@nobits
 	.globl	local_var