[PATCH] D21236: AMDGPU/SI: Correctly encode constant expressions

[Tom Stellard via llvm-commits]

tstellarAMD created this revision.
tstellarAMD added reviewers: artem.tamazov, vpykhtin, SamWot, nhaustov, arsenm.
tstellarAMD added a subscriber: llvm-commits.
Herald added subscribers: kzhuravl, arsenm.

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

http://reviews.llvm.org/D21236

Files:
  lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
  test/MC/AMDGPU/expressions.s

Index: test/MC/AMDGPU/expressions.s
===================================================================
--- test/MC/AMDGPU/expressions.s
+++ test/MC/AMDGPU/expressions.s
@@ -29,3 +29,13 @@
 s_addc_u32 s1, s1, 0
 // VI: s_add_u32 s0, s0, global+4
 // VI: s_addc_u32 s1, s1, 0
+
+// Use a computed expression that results in an inline immediate.
+.set foo, 4
+s_mov_b32 s0, foo+2
+// VI: s_mov_b32 s0, 6 ; encoding: [0x86,0x00,0x80,0xbe]
+
+// Use a computed expression that results in a non-inline immediate.
+.set foo, 512
+s_mov_b32 s0, foo+2
+// VI: s_mov_b32 s0, 514 ; encoding: [0xff,0x00,0x80,0xbe,0x02,0x02,0x00,0x00]
Index: lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
===================================================================
--- lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
+++ lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp
@@ -162,20 +162,30 @@
 
 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 @@
 
     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 @@
   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())


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