[PATCH] [mips] [IAS] Fix negation of 32-bit immediates.

[Toma Tabacu]

Hi dsanders,

Because immediates are stored as int64_t internally, negating a 32-bit immediate will result in a 64-bit value,
which will cause an error if the associated instruction only accepts 32-bit immediates.

To maintain compatibility with GAS we need to clear the upper 32 bits of a negated value,
unless it's a 16-bit value, for which we should use an ADDIU.

http://reviews.llvm.org/D8662

Files:
  lib/Target/Mips/AsmParser/MipsAsmParser.cpp
  test/MC/Mips/mips-expansions.s
  test/MC/Mips/mips64-expansions.s

Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1053,8 +1053,21 @@
   }
 
   static std::unique_ptr<MipsOperand>
-  CreateImm(const MCExpr *Val, SMLoc S, SMLoc E, MipsAsmParser &Parser) {
+  CreateImm(const MCExpr *Val, SMLoc S, SMLoc E, MipsAsmParser &Parser, bool IsNegated = false) {
     auto Op = make_unique<MipsOperand>(k_Immediate, Parser);
+    const MCConstantExpr *ValCstExpr = static_cast<const MCConstantExpr *>(Val);
+    int64_t ValInt = ValCstExpr->getValue();
+
+    // We don't clear the upper 32 bits for 16-bit negated values.
+    if (IsNegated && !(ValInt < 0 && ValInt >= -32768)) {
+      // Clear the upper 32 bits.
+      uint32_t NewValInt = ValInt & 0xffffffff;
+
+      // Replace the previous Value with our NewVal.
+      const MCConstantExpr *NewValConstExpr = MCConstantExpr::Create(
+          NewValInt, Parser.getContext());
+      Val = NewValConstExpr;
+    }
     Op->Imm.Val = Val;
     Op->StartLoc = S;
     Op->EndLoc = E;
@@ -2903,13 +2916,19 @@
     break;
   }
 
+  // If the immediate was negated, we clear the upper 32 bits of the negated
+  // value (unless it's a 16-bit value).
+  bool IsNegated = false;
+  if (getLexer().is(AsmToken::Tilde))
+    IsNegated = true;
+
   const MCExpr *IdVal;
   SMLoc S = Parser.getTok().getLoc();
   if (getParser().parseExpression(IdVal))
     return MatchOperand_ParseFail;
 
   SMLoc E = SMLoc::getFromPointer(Parser.getTok().getLoc().getPointer() - 1);
-  Operands.push_back(MipsOperand::CreateImm(IdVal, S, E, *this));
+  Operands.push_back(MipsOperand::CreateImm(IdVal, S, E, *this, IsNegated));
   return MatchOperand_Success;
 }
 
Index: test/MC/Mips/mips-expansions.s
===================================================================
--- test/MC/Mips/mips-expansions.s
+++ test/MC/Mips/mips-expansions.s
@@ -9,6 +9,8 @@
 # CHECK: lui     $7, 1               # encoding: [0x01,0x00,0x07,0x3c]
 # CHECK: ori     $7, $7, 2           # encoding: [0x02,0x00,0xe7,0x34]
 # CHECK: addiu   $8, $zero, -8       # encoding: [0xf8,0xff,0x08,0x24]
+# CHECK: lui     $10, 65519          # encoding: [0xef,0xff,0x0a,0x3c]
+# CHECK: ori     $10, $10, 61423     # encoding: [0xef,0xef,0x4a,0x35]
 
 # CHECK: addiu   $4, $zero, 20       # encoding: [0x14,0x00,0x04,0x24]
 # CHECK: lui     $7, 1               # encoding: [0x01,0x00,0x07,0x3c]
@@ -59,6 +61,7 @@
     li $6,-2345
     li $7,65538
     li $8, ~7
+    li $10, ~(0x101010)
 
     la $a0, 20
     la $7,65538
Index: test/MC/Mips/mips64-expansions.s
===================================================================
--- test/MC/Mips/mips64-expansions.s
+++ test/MC/Mips/mips64-expansions.s
@@ -207,3 +207,13 @@
 	dli	$t0, -100000000000000000
 	dli	$t0, -1000000000000000000
 	dli	$t0, -10000000000000000000
+
+  li $10, ~(0x101010)
+# CHECK: lui	$10, 65519      # encoding: [0xef,0xff,0x0a,0x3c]
+# CHECK: ori	$10, $10, 61423 # encoding: [0xef,0xef,0x4a,0x35]
+# CHECK-NOT: dsll
+
+  dli $10, ~(0x202020)
+# CHECK: lui	$10, 65503      # encoding: [0xdf,0xff,0x0a,0x3c]
+# CHECK: ori	$10, $10, 57311 # encoding: [0xdf,0xdf,0x4a,0x35]
+# CHECK-NOT: dsll

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