Fix SEH table addresses for Windows

Issue Details:
The addresses for SEH tables for Windows are incorrect as 1 was unconditionally being added to all addresses. +1 is required for the SEH end address (as it is exclusive), but the SEH start addresses is inclusive and so should be used as-is.

In the IP2State tables, the addresses are +1 for AMD64 to handle the return address for a call being after the actual call instruction but are as-is for ARM and ARM64 as the `StateFromIp` function in the VC runtime automatically takes this into account and adjusts the address that is it looking up.

Fix Details:
* Split the `getLabel` function into two: `getLabel` (used for the SEH start address and ARM+ARM64 IP2State addresses) and `getLabelPlusOne` (for the SEH end address, and AMD64 IP2State addresses).

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D107784

1 files changed, 18 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/WinException.cpp b/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
index b30d9cc1..ef57031 100644
--- a/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
@@ -43,6 +43,7 @@ WinException::WinException(AsmPrinter *A) : EHStreamer(A) {
   // platforms use an imagerel32 relocation to refer to symbols.
   useImageRel32 = (A->getDataLayout().getPointerSizeInBits() == 64);
   isAArch64 = Asm->TM.getTargetTriple().isAArch64();
+  isThumb = Asm->TM.getTargetTriple().isThumb();
 }
 
 WinException::~WinException() {}
@@ -330,10 +331,12 @@ const MCExpr *WinException::create32bitRef(const GlobalValue *GV) {
 }
 
 const MCExpr *WinException::getLabel(const MCSymbol *Label) {
-  if (isAArch64)
-    return MCSymbolRefExpr::create(Label, MCSymbolRefExpr::VK_COFF_IMGREL32,
-                                   Asm->OutContext);
-  return MCBinaryExpr::createAdd(create32bitRef(Label),
+  return MCSymbolRefExpr::create(Label, MCSymbolRefExpr::VK_COFF_IMGREL32,
+                                 Asm->OutContext);
+}
+
+const MCExpr *WinException::getLabelPlusOne(const MCSymbol *Label) {
+  return MCBinaryExpr::createAdd(getLabel(Label),
                                  MCConstantExpr::create(1, Asm->OutContext),
                                  Asm->OutContext);
 }
@@ -561,8 +564,8 @@ InvokeStateChangeIterator &InvokeStateChangeIterator::scan() {
 ///   struct Table {
 ///     int NumEntries;
 ///     struct Entry {
-///       imagerel32 LabelStart;
-///       imagerel32 LabelEnd;
+///       imagerel32 LabelStart;       // Inclusive
+///       imagerel32 LabelEnd;         // Exclusive
 ///       imagerel32 FilterOrFinally;  // One means catch-all.
 ///       imagerel32 LabelLPad;        // Zero means __finally.
 ///     } Entries[NumEntries];
@@ -664,7 +667,7 @@ void WinException::emitSEHActionsForRange(const WinEHFuncInfo &FuncInfo,
     AddComment("LabelStart");
     OS.emitValue(getLabel(BeginLabel), 4);
     AddComment("LabelEnd");
-    OS.emitValue(getLabel(EndLabel), 4);
+    OS.emitValue(getLabelPlusOne(EndLabel), 4);
     AddComment(UME.IsFinally ? "FinallyFunclet" : UME.Filter ? "FilterFunction"
                                                              : "CatchAll");
     OS.emitValue(FilterOrFinally, 4);
@@ -949,8 +952,15 @@ void WinException::computeIP2StateTable(
       if (!ChangeLabel)
         ChangeLabel = StateChange.PreviousEndLabel;
       // Emit an entry indicating that PCs after 'Label' have this EH state.
+      // NOTE: On ARM architectures, the StateFromIp automatically takes into
+      // account that the return address is after the call instruction (whose EH
+      // state we should be using), but on other platforms we need to +1 to the
+      // label so that we are using the correct EH state.
+      const MCExpr *LabelExpression = (isAArch64 || isThumb)
+                                          ? getLabel(ChangeLabel)
+                                          : getLabelPlusOne(ChangeLabel);
       IPToStateTable.push_back(
-          std::make_pair(getLabel(ChangeLabel), StateChange.NewState));
+          std::make_pair(LabelExpression, StateChange.NewState));
       // FIXME: assert that NewState is between CatchLow and CatchHigh.
     }
   }