[PATCH] [mips] [IAS] Fix expansion of LASym with negative offset.

[Toma Tabacu]

Rebased (for Sean Bruno's convenience).


http://reviews.llvm.org/D9346

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

Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -2643,8 +2643,21 @@
       return MipsMCExpr::create(VK, Expr, getContext());
 
     const MCExpr *LExp = evaluateRelocExpr(BE->getLHS(), RelocStr);
-    const MCExpr *RExp = evaluateRelocExpr(BE->getRHS(), RelocStr);
-    Res = MCBinaryExpr::create(BE->getOpcode(), LExp, RExp, getContext());
+    // If the RHS is a constant and we are subtracting it, switch the
+    // MCBinaryExpr to be the addition of the negated RHS constant with the
+    // unchanged LHS.
+    if (BE->getOpcode() == MCBinaryExpr::Sub &&
+        isa<MCConstantExpr>(BE->getRHS())) {
+      const MCConstantExpr *OldRExp = cast<MCConstantExpr>(BE->getRHS());
+      const MCExpr *NewRExp =
+          MCConstantExpr::create(-OldRExp->getValue(), getContext());
+
+      const MCExpr *RExp = evaluateRelocExpr(NewRExp, RelocStr);
+      Res = MCBinaryExpr::create(MCBinaryExpr::Add, LExp, RExp, getContext());
+    } else {
+      const MCExpr *RExp = evaluateRelocExpr(BE->getRHS(), RelocStr);
+      Res = MCBinaryExpr::create(BE->getOpcode(), LExp, RExp, getContext());
+    }
     return Res;
   }
 
Index: test/MC/Mips/mips-expansions.s
===================================================================
--- test/MC/Mips/mips-expansions.s
+++ test/MC/Mips/mips-expansions.s
@@ -58,6 +58,26 @@
 # CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_HI, kind: fixup_Mips_HI16
 # CHECK: ori $8, $8, %lo(symbol+4369)  # encoding: [0x11'A',0x11'A',0x08,0x35]
 # CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
+  la $8, symbol-1
+# CHECK: lui $8, %hi(symbol)           # encoding: [A,A,0x08,0x3c]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_HI, kind: fixup_Mips_HI16
+# CHECK: ori $8, $8, %lo(symbol-1)     # encoding: [0xff'A',0xff'A',0x08,0x35]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
+  la $8, symbol-32770
+# CHECK: lui $8, %hi(symbol-1)         # encoding: [0xff'A',0xff'A',0x08,0x3c]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_HI, kind: fixup_Mips_HI16
+# CHECK: ori $8, $8, %lo(symbol+32766) # encoding: [0xfe'A',0x7f'A',0x08,0x35]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
+  la $8, symbol-65538
+# CHECK: lui $8, %hi(symbol-1)         # encoding: [0xff'A',0xff'A',0x08,0x3c]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_HI, kind: fixup_Mips_HI16
+# CHECK: ori $8, $8, %lo(symbol-2)     # encoding: [0xfe'A',0xff'A',0x08,0x35]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
+  la $8, symbol-0x11111
+# CHECK: lui $8, %hi(symbol-1)         # encoding: [0xff'A',0xff'A',0x08,0x3c]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_HI, kind: fixup_Mips_HI16
+# CHECK: ori $8, $8, %lo(symbol-4369)  # encoding: [0xef'A',0xee'A',0x08,0x35]
+# CHECK:                               #   fixup A - offset: 0, value: symbol at ABS_LO, kind: fixup_Mips_LO16
 
 # LW/SW and LDC1/SDC1 of symbol address, done by MipsAsmParser::expandMemInst():
   .set noat

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