Remove a processFixupValue hack.

The intention of processFixupValue is not to redefine the semantics of
MCExpr. It is odd enough that a expression lowers to a PCRel MCExpr or
not depending on what it looks like. At least it is a local hack now.

I left a fix for anyone trying to figure out what producers should be
producing a different expression.

llvm-svn: 306200

1 files changed, 32 insertions, 4 deletions

diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
index 21da8b6b700..553a752820d 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
@@ -363,6 +363,25 @@ SIMCCodeEmitter::getSDWAVopcDstEncoding(const MCInst &MI, unsigned OpNo,
   return RegEnc;
 }
 
+static bool needsPCRel(const MCExpr *Expr) {
+  switch (Expr->getKind()) {
+  case MCExpr::SymbolRef:
+    return true;
+  case MCExpr::Binary: {
+    auto *BE = cast<MCBinaryExpr>(Expr);
+    if (BE->getOpcode() == MCBinaryExpr::Sub)
+      return false;
+    return needsPCRel(BE->getLHS()) || needsPCRel(BE->getRHS());
+  }
+  case MCExpr::Unary:
+    return needsPCRel(cast<MCUnaryExpr>(Expr)->getSubExpr());
+  case MCExpr::Target:
+  case MCExpr::Constant:
+    return false;
+  }
+  llvm_unreachable("invalid kind");
+}
+
 uint64_t SIMCCodeEmitter::getMachineOpValue(const MCInst &MI,
                                             const MCOperand &MO,
                                        SmallVectorImpl<MCFixup> &Fixups,
@@ -371,12 +390,21 @@ uint64_t SIMCCodeEmitter::getMachineOpValue(const MCInst &MI,
     return MRI.getEncodingValue(MO.getReg());
 
   if (MO.isExpr() && MO.getExpr()->getKind() != MCExpr::Constant) {
-    const auto *Expr = dyn_cast<MCSymbolRefExpr>(MO.getExpr());
+    // FIXME: If this is expression is PCRel or not should not depend on what
+    // the expression looks like. Given that this is just a general expression,
+    // it should probably be FK_Data_4 and whatever is producing
+    //
+    //    s_add_u32 s2, s2, (extern_const_addrspace+16
+    //
+    // And expecting a PCRel should instead produce
+    //
+    // .Ltmp1:
+    //   s_add_u32 s2, s2, (extern_const_addrspace+16)-.Ltmp1
     MCFixupKind Kind;
-    if (Expr && Expr->getSymbol().isExternal())
-      Kind = FK_Data_4;
-    else
+    if (needsPCRel(MO.getExpr()))
       Kind = FK_PCRel_4;
+    else
+      Kind = FK_Data_4;
     Fixups.push_back(MCFixup::create(4, MO.getExpr(), Kind, MI.getLoc()));
   }