LLVM puts padding bytes in the __gcc_except_tab section after the

GCC_except_table label but before the Lexception, which the FDE references.
This causes problems as the FDE does not point to the start of an LSDA chunk.

Use an unnormalized uleb128 for the call-site table length that includes the
padding.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97078 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 37 insertions, 35 deletions

diff --git a/lib/CodeGen/AsmPrinter/DwarfException.cpp b/lib/CodeGen/AsmPrinter/DwarfException.cpp
index c6c59f5998..2e10a4a637 100644
--- a/lib/CodeGen/AsmPrinter/DwarfException.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfException.cpp
@@ -638,18 +638,18 @@ void DwarfException::EmitExceptionTable() {
   const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
   bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
   bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
-  unsigned SizeSites;
+  unsigned CallSiteTableLength;
 
   if (IsSJLJ)
-    SizeSites = 0;
+    CallSiteTableLength = 0;
   else
-    SizeSites = CallSites.size() *
+    CallSiteTableLength = CallSites.size() *
       (SiteStartSize + SiteLengthSize + LandingPadSize);
 
   for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
-    SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
+    CallSiteTableLength += MCAsmInfo::getULEB128Size(CallSites[i].Action);
     if (IsSJLJ)
-      SizeSites += MCAsmInfo::getULEB128Size(i);
+      CallSiteTableLength += MCAsmInfo::getULEB128Size(i);
   }
 
   // Type infos.
@@ -698,7 +698,20 @@ void DwarfException::EmitExceptionTable() {
   Asm->OutStreamer.SwitchSection(LSDASection);
   Asm->EmitAlignment(2, 0, 0, false);
 
+  // Emit the LSDA.
   O << "GCC_except_table" << SubprogramCount << ":\n";
+  EmitLabel("exception", SubprogramCount);
+
+  if (IsSJLJ) {
+    SmallString<16> LSDAName;
+    raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
+      "_LSDA_" << Asm->getFunctionNumber();
+    O << LSDAName.str() << ":\n";
+  }
+
+  // Emit the LSDA header.
+  EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
+  EmitEncodingByte(TTypeEncoding, "@TType");
 
   // The type infos need to be aligned. GCC does this by inserting padding just
   // before the type infos. However, this changes the size of the exception
@@ -707,7 +720,7 @@ void DwarfException::EmitExceptionTable() {
   // So by increasing the size by inserting padding, you may increase the number
   // of bytes used for writing the size. If it increases, say by one byte, then
   // you now need to output one less byte of padding to get the type infos
-  // aligned.  However this decreases the size of the exception table. This
+  // aligned. However this decreases the size of the exception table. This
   // changes the value you have to output for the exception table size. Due to
   // the variable length encoding, the number of bytes used for writing the
   // length may decrease. If so, you then have to increase the amount of
@@ -716,41 +729,30 @@ void DwarfException::EmitExceptionTable() {
   // We chose another solution: don't output padding inside the table like GCC
   // does, instead output it before the table.
   unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
-  unsigned TyOffset = sizeof(int8_t) +          // Call site format
-    MCAsmInfo::getULEB128Size(SizeSites) +      // Call site table length
-    SizeSites + SizeActions + SizeTypes;
-  unsigned TotalSize = sizeof(int8_t) +         // LPStart format
-                       sizeof(int8_t) +         // TType format
-    (HaveTTData ?
-     MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
-    TyOffset;
+  unsigned CallSiteTableLengthSize =
+    MCAsmInfo::getULEB128Size(CallSiteTableLength);
+  unsigned TTypeBaseOffset =
+    sizeof(int8_t) +                            // Call site format
+    CallSiteTableLengthSize +                   // Call site table length size
+    CallSiteTableLength +                       // Call site table length
+    SizeActions +                               // Actions size
+    SizeTypes;
+  unsigned TTypeBaseOffsetSize = MCAsmInfo::getULEB128Size(TTypeBaseOffset);
+  unsigned TotalSize =
+    sizeof(int8_t) +                            // LPStart format
+    sizeof(int8_t) +                            // TType format
+    (HaveTTData ? TTypeBaseOffsetSize : 0) +    // TType base offset size
+    TTypeBaseOffset;                            // TType base offset
   unsigned SizeAlign = (4 - TotalSize) & 3;
 
-  for (unsigned i = 0; i != SizeAlign; ++i) {
-    Asm->EmitInt8(0);
-    EOL("Padding");
-  }
-
-  EmitLabel("exception", SubprogramCount);
-
-  if (IsSJLJ) {
-    SmallString<16> LSDAName;
-    raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
-      "_LSDA_" << Asm->getFunctionNumber();
-    O << LSDAName.str() << ":\n";
-  }
-
-  // Emit the header.
-  EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
-  EmitEncodingByte(TTypeEncoding, "@TType");
-
   if (HaveTTData)
-    EmitULEB128(TyOffset, "@TType base offset");
+    // Pad here for alignment.
+    EmitULEB128(TTypeBaseOffset + SizeAlign, "@TType base offset");
 
   // SjLj Exception handling
   if (IsSJLJ) {
     EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
-    EmitULEB128(SizeSites, "Call site table length");
+    EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
 
     // Emit the landing pad site information.
     unsigned idx = 0;
@@ -791,7 +793,7 @@ void DwarfException::EmitExceptionTable() {
 
     // Emit the landing pad call site table.
     EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
-    EmitULEB128(SizeSites, "Call site table length");
+    EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
 
     for (SmallVectorImpl<CallSiteEntry>::const_iterator
          I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {