PowerPC: Use shouldAssumeDSOLocal in classifyGlobalReference

[• rafael]

Summary

And teach shouldAssumeDSOLocal that ppc has no copy relocations.

The resulting code handlen a few more case than before. For example, it
knows that a weak symbol can be resolved to another .o file, but it
will still be in the main executable.

[• rafael]

adding llvm-commits

[• rafael]

ping

[sfertile]

@Rafael Are you still interested in getting this patch reviewed?

[hfinkel]

So you can't interpose weak symbols on PPC?

lib/Target/TargetMachine.cpp

161

We should add a comment here that PPC does not use copy relocations.

[• rafael]

rebase and add comment.

[hfinkel]

LGTM

lib/Target/PowerPC/PPCSubtarget.cpp

bool PPCSubtarget::useAA() const {
   // Use AA during code generation for the embedded cores.
   return needsAggressiveScheduling(DarwinDirective);
 }
 
 bool PPCSubtarget::enableSubRegLiveness() const {
   return UseSubRegLiveness;
 }
 
-unsigned char PPCSubtarget::classifyGlobalReference(
-    const GlobalValue *GV) const {
+unsigned char
+PPCSubtarget::classifyGlobalReference(const GlobalValue *GV) const {
   // Note that currently we don't generate non-pic references.
   // If a caller wants that, this will have to be updated.
 
   // Large code model always uses the TOC even for local symbols.
   if (TM.getCodeModel() == CodeModel::Large)
     return PPCII::MO_PIC_FLAG | PPCII::MO_NLP_FLAG;
 
-  unsigned char flags = PPCII::MO_PIC_FLAG;
-
-  // Only if the relocation mode is PIC do we have to worry about
-  // interposition. In all other cases we can use a slightly looser standard to
-  // decide how to access the symbol.
-  if (TM.getRelocationModel() == Reloc::PIC_) {
-    // If it's local, or it's non-default, it can't be interposed.
-    if (!GV->hasLocalLinkage() &&
-        GV->hasDefaultVisibility()) {
-      flags |= PPCII::MO_NLP_FLAG;
-    }
-    return flags;
-  }
-
-  if (GV->isStrongDefinitionForLinker())
-    return flags;
-  return flags | PPCII::MO_NLP_FLAG;
+  if (TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
+    return PPCII::MO_PIC_FLAG;
+  return PPCII::MO_PIC_FLAG | PPCII::MO_NLP_FLAG;
 }
 
 bool PPCSubtarget::isELFv2ABI() const { return TM.isELFv2ABI(); }
 bool PPCSubtarget::isPPC64() const { return TM.isPPC64(); }

lib/Target/TargetMachine.cpp

bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
   if (IsExecutable) {
     // If the symbol is defined, it cannot be preempted.
     if (GV && !GV->isDeclarationForLinker())
       return true;
 
     bool IsTLS = GV && GV->isThreadLocal();
     bool IsAccessViaCopyRelocs =
         Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);
-    // Check if we can use copy relocations.
-    if (!IsTLS && (RM == Reloc::Static || IsAccessViaCopyRelocs))
+    Triple::ArchType Arch = TT.getArch();
+    bool IsPPC =
+        Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
+    // Check if we can use copy relocations. PowerPC has no copy relocations.
+    if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
       return true;
   }
 
   // ELF supports preemption of other symbols.
   return false;
 }
 
 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {

test/CodeGen/PowerPC/fast-isel-load-store.ll

 }
 
 ;; std requires an offset that fits in 16 bits, so we need stdx here.
 define void @t17(i64 %v) nounwind {
 ; ELF64: t17
   %1 = add nsw i64 %v, 1
   store i64 %1, i64* getelementptr inbounds ([8192 x i64], [8192 x i64]* @i, i32 0, i64 5000), align 8
 ; ELF64: addis
-; ELF64: ld
+; ELF64: addi
 ; ELF64: addi
 ; ELF64: lis
 ; ELF64: ori
 ; ELF64: stdx
   ret void
 }
 

test/CodeGen/PowerPC/mcm-obj.ll

 define signext i32 @test_tentative() nounwind {
 entry:
   %0 = load i32, i32* @ti, align 4
   %inc = add nsw i32 %0, 1
   store i32 %inc, i32* @ti, align 4
   ret i32 %0
 }
 
-; Verify generation of R_PPC64_TOC16_HA and R_PPC64_TOC16_LO_DS for
-; accessing tentatively declared variable ti.
+; Verify generation of relocations foraccessing variable ti.
 ;
 ; MEDIUM-NEXT:     0x{{[0-9,A-F]+}} R_PPC64_TOC16_HA [[SYM6:[^ ]+]]
-; MEDIUM-NEXT:     0x{{[0-9,A-F]+}} R_PPC64_TOC16_LO_DS [[SYM6]]
+; MEDIUM-NEXT:     0x{{[0-9,A-F]+}} R_PPC64_TOC16_LO [[SYM6]]
 ;
 ; LARGE-NEXT:      0x{{[0-9,A-F]+}} R_PPC64_TOC16_HA [[SYM6:[^ ]+]]
 ; LARGE-NEXT:      0x{{[0-9,A-F]+}} R_PPC64_TOC16_LO_DS [[SYM6]]
 
 define i8* @test_fnaddr() nounwind {
 entry:
   %func = alloca i32 (i32)*, align 8
   store i32 (i32)* @foo, i32 (i32)** %func, align 8