Propagate types from symbol to aliases.

This is similar, but not identical to what gas does. The logic in MC is to just
compute the symbol table after parsing the entire file. GAS is mixed, given

.type b, @object
a = b
b:
.type b, @function

It will propagate the change and make 'a' a function. Given

.type b, @object
b:
a = b
.type b, @function

the type of 'a' is still object.

Since we do the computation in the end, we produce a function in both cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204555 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index dc77e0361c5aa246b54e4e362637f531a6a3b6f4..076b99930774229838467d0d86cfb2c97158fdc0 100644 (file)
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -575,6 +575,22 @@ static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
   return Type;
 }
 
+static const MCSymbol *getBaseSymbol(const MCAsmLayout &Layout,
+                                     const MCSymbol &Symbol) {
+  if (!Symbol.isVariable())
+    return &Symbol;
+
+  const MCExpr *Expr = Symbol.getVariableValue();
+  MCValue Value;
+  if (!Expr->EvaluateAsRelocatable(Value, &Layout))
+    llvm_unreachable("Invalid Expression");
+  assert(!Value.getSymB());
+  const MCSymbolRefExpr *A = Value.getSymA();
+  if (!A)
+    return nullptr;
+  return getBaseSymbol(Layout, A->getSymbol());
+}
+
 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
                                   MCDataFragment *ShndxF,
                                   ELFSymbolData &MSD,
@@ -588,7 +604,12 @@ void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
 
   // Binding and Type share the same byte as upper and lower nibbles
   uint8_t Binding = MCELF::GetBinding(OrigData);
-  uint8_t Type = mergeTypeForSet(MCELF::GetType(OrigData), MCELF::GetType(Data));
+  uint8_t Type = MCELF::GetType(OrigData);
+  const MCSymbol *Base = getBaseSymbol(Layout, OrigData.getSymbol());
+  if (Base) {
+    MCSymbolData BaseSD = Layout.getAssembler().getSymbolData(*Base);
+    Type = mergeTypeForSet(Type, MCELF::GetType(BaseSD));
+  }
   if (OrigData.getFlags() & ELF_Other_ThumbFunc)
     Type = ELF::STT_FUNC;
   uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);

diff --git a/test/MC/ELF/type-propagate.s b/test/MC/ELF/type-propagate.s
new file mode 100644 (file)
index 0000000..449b890
--- /dev/null
+++ b/test/MC/ELF/type-propagate.s
@@ -0,0 +1,157 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -t - | FileCheck %s
+
+// This tests that types are propagated from symbols to their aliases. Our
+// behavior is a bit different than gas. If the type of a symbol changes,
+// gas will update the type of the aliases only if those aliases were declare
+// at a point in the file where the aliased symbol was already define.
+
+// The lines marked with GAS illustrate this difference.
+
+
+       .type sym01, @object
+sym01:
+       .type sym02, @function
+sym02:
+
+       sym03 = sym01
+       sym04 = sym03
+.type sym03, @function
+       sym05 = sym03
+       sym06 = sym01 - sym02
+       sym07 = sym02 - sym01
+
+       sym08 = sym10
+       sym09 = sym10 + 1
+       .type sym10, @object
+sym10:
+
+       sym11 = sym10
+       sym12 = sym10 + 1
+       .type sym10, @function
+
+// CHECK:       Symbol {
+// CHECK:         Name: sym01
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: Object (0x1)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym02
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: Function (0x2)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym03
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: Function (0x2)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym04
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: Object (0x1)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym05
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+
+// GAS:           Type: Function (0x2)
+// CHECK-NEXT:    Type: Object (0x1)
+
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym06
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: None (0x0)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section:  (0xFFF1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym07
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: None (0x0)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section:  (0xFFF1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym08
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: Function (0x2)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym09
+// CHECK-NEXT:    Value: 0x1
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+
+// GAS:           Type: None (0x0)
+// CHECK-NEXT:    Type: Function (0x2)
+
+// CHECK-NEXT:    Other: 0
+
+// GAS:           Section: .text (0x1)
+// CHECK-NEXT:    Section: (0xFFF1)
+
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym10
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+// CHECK-NEXT:    Type: Function (0x2)
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym11
+// CHECK-NEXT:    Value: 0x0
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+
+// GAS:           Type: Object (0x1)
+// CHECK-NEXT:    Type: Function (0x2)
+
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .text (0x1)
+// CHECK-NEXT:  }
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym12
+// CHECK-NEXT:    Value: 0x1
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Local (0x0)
+
+// GAS:           Type: Object (0x1)
+// CHECK-NEXT:    Type: Function (0x2)
+
+// CHECK-NEXT:    Other: 0
+
+// GAS:           Section: .text (0x1)
+// CHECK-NEXT:    Section: (0xFFF1)
+
+// CHECK-NEXT:  }