[AsmPrinter] Make the encoding of call sites in .gcc_except_table configurable and...

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

diff --git a/llvm/include/llvm/CodeGen/AsmPrinter.h b/llvm/include/llvm/CodeGen/AsmPrinter.h
index 9c2097b..d110f8b 100644 (file)
--- a/llvm/include/llvm/CodeGen/AsmPrinter.h
+++ b/llvm/include/llvm/CodeGen/AsmPrinter.h
@@ -543,6 +543,12 @@ public:
     emitDwarfStringOffset(S.getEntry());
   }
 
+  /// Emit reference to a call site with a specified encoding
+  void EmitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
+                          unsigned Encoding) const;
+  /// Emit an integer value corresponding to the call site encoding
+  void EmitCallSiteValue(uint64_t Value, unsigned Encoding) const;
+
   /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
   virtual unsigned getISAEncoding() { return 0; }
 

diff --git a/llvm/include/llvm/Target/TargetLoweringObjectFile.h b/llvm/include/llvm/Target/TargetLoweringObjectFile.h
index 7e094a1..3a2497b 100644 (file)
--- a/llvm/include/llvm/Target/TargetLoweringObjectFile.h
+++ b/llvm/include/llvm/Target/TargetLoweringObjectFile.h
@@ -51,6 +51,7 @@ protected:
   unsigned PersonalityEncoding = 0;
   unsigned LSDAEncoding = 0;
   unsigned TTypeEncoding = 0;
+  unsigned CallSiteEncoding = 0;
 
   /// This section contains the static constructor pointer list.
   MCSection *StaticCtorSection = nullptr;
@@ -147,6 +148,7 @@ public:
   unsigned getPersonalityEncoding() const { return PersonalityEncoding; }
   unsigned getLSDAEncoding() const { return LSDAEncoding; }
   unsigned getTTypeEncoding() const { return TTypeEncoding; }
+  unsigned getCallSiteEncoding() const { return CallSiteEncoding; }
 
   const MCExpr *getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding,
                                   MCStreamer &Streamer) const;

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp
index 7bc64d0..992e44d 100644 (file)
--- 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 2786f8d..99e3687 100644 (file)
--- 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 d8e6b3e..4c8f75b 100644 (file)
--- 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;

diff --git a/llvm/lib/Target/TargetLoweringObjectFile.cpp b/llvm/lib/Target/TargetLoweringObjectFile.cpp
index ee32d01..17274e1 100644 (file)
--- a/llvm/lib/Target/TargetLoweringObjectFile.cpp
+++ b/llvm/lib/Target/TargetLoweringObjectFile.cpp
@@ -47,6 +47,7 @@ void TargetLoweringObjectFile::Initialize(MCContext &ctx,
 
   // Reset various EH DWARF encodings.
   PersonalityEncoding = LSDAEncoding = TTypeEncoding = dwarf::DW_EH_PE_absptr;
+  CallSiteEncoding = dwarf::DW_EH_PE_uleb128;
 }
 
 TargetLoweringObjectFile::~TargetLoweringObjectFile() {

diff --git a/llvm/test/CodeGen/RISCV/dwarf-eh.ll b/llvm/test/CodeGen/RISCV/dwarf-eh.ll
index 67236d7..ecca817 100644 (file)
--- a/llvm/test/CodeGen/RISCV/dwarf-eh.ll
+++ b/llvm/test/CodeGen/RISCV/dwarf-eh.ll
@@ -53,14 +53,14 @@ try.cont:
 ; CHECK-NEXT: .byte 155 # @TType Encoding = indirect pcrel sdata4
 ; TODO: call site encoding should be DW_EH_PE_udata4
 ; CHECK: .Lttbaseref0:
-; CHECK-NEXT: .byte    1                       # Call site Encoding = uleb128
+; CHECK-NEXT: .byte    3                       # Call site Encoding = udata4
 ; CHECK-NEXT: .uleb128 .Lcst_end0-.Lcst_begin0
 ; CHECK-NEXT: cst_begin0:
-; CHECK-NEXT: .uleb128 .Ltmp0-.Lfunc_begin0   # >> Call Site 1 <<
-; CHECK-NEXT: .uleb128 .Ltmp1-.Ltmp0          #   Call between .Ltmp0 and .Ltmp1
-; CHECK-NEXT: .uleb128 .Ltmp2-.Lfunc_begin0   #     jumps to .Ltmp2
+; CHECK-NEXT: .word .Ltmp0-.Lfunc_begin0   # >> Call Site 1 <<
+; CHECK-NEXT: .word .Ltmp1-.Ltmp0          #   Call between .Ltmp0 and .Ltmp1
+; CHECK-NEXT: .word .Ltmp2-.Lfunc_begin0   #     jumps to .Ltmp2
 ; CHECK-NEXT: .byte    1                       #   On action: 1
-; CHECK-NEXT: .uleb128 .Ltmp1-.Lfunc_begin0   # >> Call Site 2 <<
-; CHECK-NEXT: .uleb128 .Lfunc_end0-.Ltmp1     #   Call between .Ltmp1 and .Lfunc_end0
-; CHECK-NEXT: .byte    0                       #     has no landing pad
+; CHECK-NEXT: .word .Ltmp1-.Lfunc_begin0   # >> Call Site 2 <<
+; CHECK-NEXT: .word .Lfunc_end0-.Ltmp1     #   Call between .Ltmp1 and .Lfunc_end0
+; CHECK-NEXT: .word    0                       #     has no landing pad
 ; CHECK-NEXT: .byte    0                       #   On action: cleanup