[PATCH] D74927: [MC][ARM] make Thumb function also if type attribute is set

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers updated this revision to Diff 325116.
nickdesaulniers edited the summary of this revision.
nickdesaulniers added a comment.

- rebase, add Peter's comment
- with D96632 <https://reviews.llvm.org/D96632> (and hacking around https://github.com/ClangBuiltLinux/linux/issues/1286) I can build a THUMB2 defconfig Linux kernel.
- with this, I can boot it.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74927/new/

https://reviews.llvm.org/D74927

Files:
  llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
  llvm/test/MC/ARM/thumb-function-address.s


Index: llvm/test/MC/ARM/thumb-function-address.s
===================================================================
--- /dev/null
+++ llvm/test/MC/ARM/thumb-function-address.s
@@ -0,0 +1,20 @@
+@ RUN: llvm-mc -filetype=obj -triple=armv7-linux-gnueabi %s -o %t
+@ RUN: llvm-readobj --symbols %t | FileCheck %s
+
+  .syntax unified
+  .text
+  .thumb
+func_label:
+  .type func_label, %function
+
+@ Check func_label address has bit 1 set.
+@ CHECK:   Symbol {
+@ CHECK:     Name: func_label (7)
+@ CHECK:     Value: 0x1
+@ CHECK:     Size: 0
+@ CHECK:     Binding: Local (0x0)
+@ CHECK:     Type: Function (0x2)
+@ CHECK:     Other: 0
+@ CHECK:     Section: .text (0x2)
+@ CHECK:   }
+
Index: llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
===================================================================
--- llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
+++ llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -579,6 +579,28 @@
     }
   }
 
+  /// If a label is defined before the .type directive sets the label's type
+  /// then the label can't be recorded as thumb function when the label is
+  /// defined. We override emitSymbolAttribute() which is called as part of the
+  /// parsing of .type so that if the symbol has already been defined we can
+  /// record the label as Thumb. FIXME: there is a corner case where the state
+  /// is changed in between the label definition and the .type directive, this
+  /// is not expected to occur in practice and handling it would require the
+  /// backend to track IsThumb for every label.
+  bool emitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override {
+    bool val = MCELFStreamer::emitSymbolAttribute(Symbol, Attribute);
+
+    if (!IsThumb)
+      return val;
+
+    unsigned Type = cast<MCSymbolELF>(Symbol)->getType();
+    if ((Type == ELF::STT_FUNC || Type == ELF::STT_GNU_IFUNC) &&
+        Symbol->isDefined())
+      getAssembler().setIsThumbFunc(Symbol);
+
+    return val;
+  };
+
 private:
   enum ElfMappingSymbol {
     EMS_None,


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