[AsmPrinter] Make the encoding of call sites in .gcc_except_table configurable and use for RISC-V

The original behavior was to always emit the offsets to each call site in the
call site table as uleb128 values, however on some architectures (eg RISCV)
these uleb128 offsets into the code cannot always be resolved until link time
(because relaxation will invalidate any calculated offsets), and there are no
appropriate relocations for uleb128 values. As a consequence it needs to be
possible to specify an alternative.

This also switches RISCV to use DW_EH_PE_udata4 for call side encodings in
.gcc_except_table

Differential Revision: https://reviews.llvm.org/D63415
Patch by Edward Jones.

llvm-svn: 366329

3 files changed, 28 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
index 7bc64d091a0..992e44d9530 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
@@ -183,6 +183,25 @@ void AsmPrinter::EmitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
   EmitLabelPlusOffset(Label, Offset, MAI->getCodePointerSize());
 }
 
+void AsmPrinter::EmitCallSiteOffset(const MCSymbol *Hi,
+                                    const MCSymbol *Lo,
+                                    unsigned Encoding) const {
+  // The least significant 3 bits specify the width of the encoding
+  if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
+    EmitLabelDifferenceAsULEB128(Hi, Lo);
+  else
+    EmitLabelDifference(Hi, Lo, GetSizeOfEncodedValue(Encoding));
+}
+
+void AsmPrinter::EmitCallSiteValue(uint64_t Value,
+                                   unsigned Encoding) const {
+  // The least significant 3 bits specify the width of the encoding
+  if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
+    EmitULEB128(Value);
+  else
+    OutStreamer->EmitIntValue(Value, GetSizeOfEncodedValue(Encoding));
+}
+
 //===----------------------------------------------------------------------===//
 // Dwarf Lowering Routines
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp
index 2786f8d9f6a..99e3687b36b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp
@@ -378,7 +378,8 @@ MCSymbol *EHStreamer::emitExceptionTable() {
   bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
   bool IsWasm = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Wasm;
   unsigned CallSiteEncoding =
-      IsSJLJ ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_uleb128;
+      IsSJLJ ? static_cast<unsigned>(dwarf::DW_EH_PE_udata4) :
+               Asm->getObjFileLowering().getCallSiteEncoding();
   bool HaveTTData = !TypeInfos.empty() || !FilterIds.empty();
 
   // Type infos.
@@ -523,24 +524,24 @@ MCSymbol *EHStreamer::emitExceptionTable() {
       // Offset of the call site relative to the start of the procedure.
       if (VerboseAsm)
         Asm->OutStreamer->AddComment(">> Call Site " + Twine(++Entry) + " <<");
-      Asm->EmitLabelDifferenceAsULEB128(BeginLabel, EHFuncBeginSym);
+      Asm->EmitCallSiteOffset(BeginLabel, EHFuncBeginSym, CallSiteEncoding);
       if (VerboseAsm)
         Asm->OutStreamer->AddComment(Twine("  Call between ") +
                                      BeginLabel->getName() + " and " +
                                      EndLabel->getName());
-      Asm->EmitLabelDifferenceAsULEB128(EndLabel, BeginLabel);
+      Asm->EmitCallSiteOffset(EndLabel, BeginLabel, CallSiteEncoding);
 
       // Offset of the landing pad relative to the start of the procedure.
       if (!S.LPad) {
         if (VerboseAsm)
           Asm->OutStreamer->AddComment("    has no landing pad");
-        Asm->EmitULEB128(0);
+        Asm->EmitCallSiteValue(0, CallSiteEncoding);
       } else {
         if (VerboseAsm)
           Asm->OutStreamer->AddComment(Twine("    jumps to ") +
                                        S.LPad->LandingPadLabel->getName());
-        Asm->EmitLabelDifferenceAsULEB128(S.LPad->LandingPadLabel,
-                                          EHFuncBeginSym);
+        Asm->EmitCallSiteOffset(S.LPad->LandingPadLabel, EHFuncBeginSym,
+                                CallSiteEncoding);
       }
 
       // Offset of the first associated action record, relative to the start of
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index d8e6b3ef93a..4c8f75b237a 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -218,6 +218,7 @@ void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
       TTypeEncoding = dwarf::DW_EH_PE_absptr;
     }
+    CallSiteEncoding = dwarf::DW_EH_PE_udata4;
     break;
   case Triple::riscv32:
   case Triple::riscv64:
@@ -226,6 +227,7 @@ void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
                           dwarf::DW_EH_PE_sdata4;
     TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
                     dwarf::DW_EH_PE_sdata4;
+    CallSiteEncoding = dwarf::DW_EH_PE_udata4;
     break;
   case Triple::sparcv9:
     LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;