[llvm] [XCOFF] make related SD symbols as isFunction (PR #69553)

[via llvm-commits]

================
@@ -1242,15 +1242,78 @@ bool XCOFFSymbolRef::isFunction() const {
 
   const XCOFFCsectAuxRef CsectAuxRef = ExpCsectAuxEnt.get();
 
-  // A function definition should be a label definition.
-  // FIXME: This is not necessarily the case when -ffunction-sections is
-  // enabled.
-  if (!CsectAuxRef.isLabel())
+  if (CsectAuxRef.getStorageMappingClass() != XCOFF::XMC_PR)
     return false;
 
-  if (CsectAuxRef.getStorageMappingClass() != XCOFF::XMC_PR)
+  // A function definition should not be a common type symbol or a external
+  // symbol.
+  if (CsectAuxRef.getSymbolType() == XCOFF::XTY_CM ||
+      CsectAuxRef.getSymbolType() == XCOFF::XTY_ER)
     return false;
 
+  // If the next symbol is a XTY_LD type symbol with same address, this XTY_SD
+  // symbol is not a function. Otherwise this is a function symbol for
+  // -ffunction-sections.
+  if (CsectAuxRef.getSymbolType() == XCOFF::XTY_SD) {
+    // If this is a csect with size 0, it won't be a function definition.
+    // This is used to hack situation that llvm always generates below symbol
+    // for -ffunction-sections:
+    // m   0x00000000     .text     1  unamex                    **No Symbol**
+    // a4  0x00000000       0    0     SD       PR    0    0
+    if (getSize() == 0)
+      return false;
+
+    Expected<uint64_t> SymbolAddressOrErr = getAddress();
+    if (!SymbolAddressOrErr) {
+      // If there is no address for this symbol, won't be a function.
+      consumeError(SymbolAddressOrErr.takeError());
+      return false;
+    }
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diggerlin wrote:

in XCOFF getAddress() will never return an error actually.

https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Object/ObjectFile.h#L462C1-L464C2 

will call 
https://github.com/llvm/llvm-project/blob/main/llvm/lib/Object/XCOFFObjectFile.cpp#L257C1-L259C2
will call
https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Object/XCOFFObjectFile.h#L791C1-L793C4


https://github.com/llvm/llvm-project/pull/69553