[PATCH] D137230: [XCOFF] avoid unnecessary Fixups when -function-sections is enabled.

[Esme Yi via Phabricator via llvm-commits]

Esme created this revision.
Esme added reviewers: shchenz, DiggerLin, PowerPC.
Herald added subscribers: kbarton, hiraditya, nemanjai.
Herald added a project: All.
Esme requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

`-xcoff-traceback-table` is a default option on AIX regardless of optimization and debug levels. 
An error of `relocation for paired relocatable term is not yet supported` in `XCOFFObjectWriter::recordRelocation` occurred when both of the `-xcoff-traceback-table` and `-function-sections` are enabled.
It is unnecessary to record relocations or resolve Fixups for the case where the symbol is the csect itself.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137230

Files:
  llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
  llvm/test/CodeGen/PowerPC/aix-xcoff-funcsect.ll


Index: llvm/test/CodeGen/PowerPC/aix-xcoff-funcsect.ll
===================================================================
--- llvm/test/CodeGen/PowerPC/aix-xcoff-funcsect.ll
+++ llvm/test/CodeGen/PowerPC/aix-xcoff-funcsect.ll
@@ -5,6 +5,11 @@
 ; RUN:     -mattr=-altivec -function-sections < %s | \
 ; RUN:   FileCheck --check-prefix=ASM %s
 
+; RUN: llc -verify-machineinstrs -mtriple powerpc64-ibm-aix-xcoff -mcpu=pwr4 \
+; RUN:     -mattr=-altivec -function-sections -xcoff-traceback-table=true \
+; RUN:     -filetype=obj -o %t.o < %s
+; RUN: llvm-objdump --syms --reloc %t.o | FileCheck --check-prefixes=XCOFF %s
+
 @alias_foo = alias void (...), bitcast (void ()* @foo to void (...)*)
 
 define void @foo() {
@@ -93,3 +98,39 @@
 ; ASM-NEXT:  	.extern	extern_foo[DS]
 ; ASM-NEXT:  	.globl	alias_foo
 ; ASM-NEXT:  	.globl	.alias_foo
+
+; XCOFF:      SYMBOL TABLE:
+; XCOFF-NEXT: 0000000000000000      df *DEBUG*	0000000000000000 <stdin>
+; XCOFF-NEXT: 0000000000000000         *UND*	0000000000000000 .extern_foo
+; XCOFF-NEXT: 0000000000000000         *UND*	0000000000000000 extern_foo
+; XCOFF-NEXT: 0000000000000000 l       .text	0000000000000000 .text
+; XCOFF-NEXT: 0000000000000000 g       .text	0000000000000019 .foo
+; XCOFF-NEXT: 0000000000000000 g     F .text (csect: .foo) 	0000000000000000 .alias_foo
+; XCOFF-NEXT: 0000000000000020 g       .text	0000000000000020 .hidden .hidden_foo
+; XCOFF-NEXT: 0000000000000040 g       .text	0000000000000059 .bar
+; XCOFF-NEXT: 00000000000000c0 l       .text	000000000000002a .static_overalign_foo
+; XCOFF-NEXT: 00000000000000f0 g     O .data	0000000000000018 foo
+; XCOFF-NEXT: 00000000000000f0 g     O .data (csect: foo) 	0000000000000000 alias_foo
+; XCOFF-NEXT: 0000000000000108 g     O .data	0000000000000018 .hidden hidden_foo
+; XCOFF-NEXT: 0000000000000120 g     O .data	0000000000000018 bar
+; XCOFF-NEXT: 0000000000000138 l     O .data	0000000000000018 static_overalign_foo
+; XCOFF-NEXT: 0000000000000150 l       .data	0000000000000000 TOC
+
+; XCOFF:      RELOCATION RECORDS FOR [.text]:
+; XCOFF-NEXT: OFFSET           TYPE                     VALUE
+; XCOFF-NEXT: 000000000000004c R_RBR                    .foo
+; XCOFF-NEXT: 0000000000000054 R_RBR                    .static_overalign_foo
+; XCOFF-NEXT: 000000000000005c R_RBR                    .alias_foo
+; XCOFF-NEXT: 0000000000000064 R_RBR                    .extern_foo
+; XCOFF-NEXT: 000000000000006c R_RBR                    .hidden_foo
+; XCOFF-NEXT: 
+; XCOFF-NEXT: RELOCATION RECORDS FOR [.data]:
+; XCOFF-NEXT: OFFSET           TYPE                     VALUE
+; XCOFF-NEXT: 0000000000000000 R_POS                    .foo
+; XCOFF-NEXT: 0000000000000008 R_POS                    TOC
+; XCOFF-NEXT: 0000000000000018 R_POS                    .hidden_foo
+; XCOFF-NEXT: 0000000000000020 R_POS                    TOC
+; XCOFF-NEXT: 0000000000000030 R_POS                    .bar
+; XCOFF-NEXT: 0000000000000038 R_POS                    TOC
+; XCOFF-NEXT: 0000000000000048 R_POS                    .static_overalign_foo
+; XCOFF-NEXT: 0000000000000050 R_POS                    TOC
Index: llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -2220,6 +2220,12 @@
   if (FirstHalfOfMandatoryField & TracebackTable::HasTraceBackTableOffsetMask) {
     MCSymbol *FuncSectSym = getObjFileLowering().getFunctionEntryPointSymbol(
         &(MF->getFunction()), TM);
+    // If the FuncSectSym is the csect itself, the difference between FuncEnd
+    // and FuncSectSym is an absolute value. To avoid evaluating an MCExpr for
+    // (FuncEnd - FuncSectSym), set the fragment of FuncEnd to FuncSectSym.
+    if (TM.getFunctionSections() && FuncSectSym->isUndefined() &&
+        FuncEnd->isDefined())
+      FuncSectSym->setFragment(FuncEnd->getFragment());
     OutStreamer->emitAbsoluteSymbolDiff(FuncEnd, FuncSectSym, 4);
   }
 


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