AMDGPU/SI: Correctly encode constant expressions

Summary:
We we have an MCConstantExpr, we can encode it directly into the instruction
instead of emitting fixups.

Reviewers: artem.tamazov, vpykhtin, SamWot, nhaustov, arsenm

Subscribers: arsenm, llvm-commits, kzhuravl

Differential Revision: http://reviews.llvm.org/D21236

Change-Id: I88b3edf288d48e65c5d705fc4850d281f8e36948
llvm-svn: 272750

1 files changed, 23 insertions, 9 deletions

diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
index 52787b64f7e..71b585c25ac 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
@@ -162,20 +162,30 @@ static uint32_t getLit64Encoding(uint64_t Val) {
 
 uint32_t SIMCCodeEmitter::getLitEncoding(const MCOperand &MO,
                                          unsigned OpSize) const {
-  if (MO.isExpr())
-    return 255;
 
-  assert(!MO.isFPImm());
+  int64_t Imm;
+  if (MO.isExpr()) {
+    const MCConstantExpr *C = dyn_cast<MCConstantExpr>(MO.getExpr());
+    if (!C)
+      return 255;
+
+    Imm = C->getValue();
+  } else {
 
-  if (!MO.isImm())
-    return ~0;
+    assert(!MO.isFPImm());
+
+    if (!MO.isImm())
+      return ~0;
+
+    Imm = MO.getImm();
+  }
 
   if (OpSize == 4)
-    return getLit32Encoding(static_cast<uint32_t>(MO.getImm()));
+    return getLit32Encoding(static_cast<uint32_t>(Imm));
 
   assert(OpSize == 8);
 
-  return getLit64Encoding(static_cast<uint64_t>(MO.getImm()));
+  return getLit64Encoding(static_cast<uint64_t>(Imm));
 }
 
 void SIMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
@@ -213,7 +223,11 @@ void SIMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
 
     if (Op.isImm())
       Imm = Op.getImm();
-    else if (!Op.isExpr()) // Exprs will be replaced with a fixup value.
+    else if (Op.isExpr()) {
+      if (const MCConstantExpr *C = dyn_cast<MCConstantExpr>(Op.getExpr()))
+        Imm = C->getValue();
+
+    } else if (!Op.isExpr()) // Exprs will be replaced with a fixup value.
       llvm_unreachable("Must be immediate or expr");
 
     for (unsigned j = 0; j < 4; j++) {
@@ -247,7 +261,7 @@ uint64_t SIMCCodeEmitter::getMachineOpValue(const MCInst &MI,
   if (MO.isReg())
     return MRI.getEncodingValue(MO.getReg());
 
-  if (MO.isExpr()) {
+  if (MO.isExpr() && MO.getExpr()->getKind() != MCExpr::Constant) {
     const MCSymbolRefExpr *Expr = dyn_cast<MCSymbolRefExpr>(MO.getExpr());
     MCFixupKind Kind;
     if (Expr && Expr->getSymbol().isExternal())