[PPC] Refine checks for emiting TOC restore nop and tail-call eligibility.

For the medium and large code models we only need to check if a call crosses
dso-boundaries when considering tail-call elgibility.

Differential Revision: https://reviews.llvm.org/D34245

llvm-svn: 311353

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -4255,13 +4255,25 @@ static int CalculateTailCallSPDiff(SelectionDAG& DAG, bool isTailCall,
 static bool isFunctionGlobalAddress(SDValue Callee);
 
 static bool
-resideInSameSection(const Function *Caller, SDValue Callee,
+callsShareTOCBase(const Function *Caller, SDValue Callee,
                     const TargetMachine &TM) {
   // If !G, Callee can be an external symbol.
   GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
   if (!G)
     return false;
 
+  // The medium and large code models are expected to provide a sufficiently
+  // large TOC to provide all data addressing needs of a module with a
+  // single TOC. Since each module will be addressed with a single TOC then we
+  // only need to check that caller and callee don't cross dso boundaries.
+  if (CodeModel::Medium == TM.getCodeModel() ||
+      CodeModel::Large == TM.getCodeModel())
+    return TM.shouldAssumeDSOLocal(*Caller->getParent(), G->getGlobal());
+
+  // Otherwise we need to ensure callee and caller are in the same section,
+  // since the linker may allocate multiple TOCs, and we don't know which
+  // sections will belong to the same TOC base.
+
   const GlobalValue *GV = G->getGlobal();
   if (!GV->isStrongDefinitionForLinker())
     return false;
@@ -4410,11 +4422,10 @@ PPCTargetLowering::IsEligibleForTailCallOptimization_64SVR4(
       !isa<ExternalSymbolSDNode>(Callee))
     return false;
 
-  // Check if Callee resides in the same section, because for now, PPC64 SVR4
+  // If the caller and callee potentially have different TOC bases then we
-  // ABI (ELFv1/ELFv2) doesn't allow tail calls to a symbol resides in another
+  // cannot tail call since we need to restore the TOC pointer after the call.
-  // section.
   // ref: https://bugzilla.mozilla.org/show_bug.cgi?id=973977
-  if (!resideInSameSection(MF.getFunction(), Callee, getTargetMachine()))
+  if (!callsShareTOCBase(MF.getFunction(), Callee, getTargetMachine()))
     return false;
 
   // TCO allows altering callee ABI, so we don't have to check further.
@@ -4996,7 +5007,7 @@ SDValue PPCTargetLowering::FinishCall(
       // any other variadic arguments).
       Ops.insert(std::next(Ops.begin()), AddTOC);
     } else if (CallOpc == PPCISD::CALL &&
-      !resideInSameSection(MF.getFunction(), Callee, DAG.getTarget())) {
+      !callsShareTOCBase(MF.getFunction(), Callee, DAG.getTarget())) {
       // Otherwise insert NOP for non-local calls.
       CallOpc = PPCISD::CALL_NOP;
     }

llvm/test/CodeGen/PowerPC/ppc64-blnop.ll

@@ -5,6 +5,8 @@
 ; RUN: llc < %s -function-sections -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu | FileCheck %s -check-prefix=CHECK-FS
 ; RUN: llc < %s -relocation-model=pic -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu | FileCheck %s
 ; RUN: llc < %s -function-sections -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu | FileCheck %s -check-prefix=CHECK-FS
+; RUN: llc < %s -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN: -code-model=small -mcpu=pwr8 | FileCheck %s -check-prefix=SCM
 
 %class.T = type { [2 x i8] }
 
@@ -74,7 +76,11 @@ define void @wo_hcaller(%class.T* %this, i8* %c) {
 
 ; CHECK-LABEL: wo_hcaller:
 ; CHECK: bl wo_hcallee
-; CHECK-NEXT: nop
+; CHECK-NOT: nop
+
+; SCM-LABEL: wo_hcaller:
+; SCM:       bl wo_hcallee
+; SCM-NEXT:  nop
 }
 
 define weak_odr protected void @wo_pcallee(%class.T* %this, i8* %c) { ret void }
@@ -84,7 +90,11 @@ define void @wo_pcaller(%class.T* %this, i8* %c) {
 
 ; CHECK-LABEL: wo_pcaller:
 ; CHECK: bl wo_pcallee
-; CHECK-NEXT: nop
+; CHECK-NOT: nop
+
+; SCM-LABEL:   wo_pcaller:
+; SCM:         bl wo_pcallee
+; SCM-NEXT:    nop
 }
 
 define weak_odr void @wo_callee(%class.T* %this, i8* %c) { ret void }
@@ -104,7 +114,11 @@ define void @w_pcaller(i8* %ptr) {
 
 ; CHECK-LABEL: w_pcaller:
 ; CHECK: bl w_pcallee
-; CHECK-NEXT: nop
+; CHECK-NOT: nop
+
+; SCM-LABEL: w_pcaller:
+; SCM:       bl w_pcallee
+; SCM-NEXT:  nop
 }
 
 define weak hidden void @w_hcallee(i8* %ptr) { ret void }
@@ -114,7 +128,11 @@ define void @w_hcaller(i8* %ptr) {
 
 ; CHECK-LABEL: w_hcaller:
 ; CHECK: bl w_hcallee
-; CHECK-NEXT: nop
+; CHECK-NOT: nop
+
+; SCM-LABEL: w_hcaller:
+; SCM:       bl w_hcallee
+; SCM-NEXT:  nop
 }
 
 define weak void @w_callee(i8* %ptr) { ret void }

llvm/test/CodeGen/PowerPC/ppc64-calls.ll

@@ -1,4 +1,6 @@
 ; RUN: llc -relocation-model=static -verify-machineinstrs < %s -mcpu=pwr7 | FileCheck %s
+; RUN: llc -relocation-model=static -verify-machineinstrs < %s -code-model=small -mcpu=pwr7 | FileCheck %s -check-prefix=SCM
+
 target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
 target triple = "powerpc64-unknown-linux-gnu"
 
@@ -21,13 +23,22 @@ define void @test_direct() nounwind readnone {
   ret void
 }
 
-; Calls to weak function requires a TOC restore 'nop' because they
+; Calls to weak function requires a TOC restore 'nop' with the small codemodel
-; may be overridden in a different module.
+; because the definition that gets choosen at link time may come from a
+; different section even though we have seen a weak definition in the same
+; section at compile time.
+; With large and medium codemodels no TOC restore is needed, since we know
+; whichever definition is choosen it resides within the same DSO boundaries and
+; therefore shares the same TOC.
 define void @test_weak() nounwind readnone {
-; CHECK-LABEL: test_weak:
   tail call void @foo_weak() nounwind
-; CHECK: bl foo
+; CHECK-LABEL: test_weak:
-; CHECK-NEXT: nop
+; CHECK: b foo_weak
+; CHECK-NOT: nop
+
+; SCM-LABEL: test_weak:
+; SCM:       bl foo_weak
+; SCM-NEXT:  nop
   ret void
 }
 

llvm/test/CodeGen/PowerPC/ppc64-sibcall.ll

@@ -1,6 +1,7 @@
 ; RUN: llc < %s -relocation-model=static -O1 -disable-ppc-sco=false -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu | FileCheck %s -check-prefix=CHECK-SCO
 ; RUN: llc < %s -relocation-model=static -O1 -disable-ppc-sco=false -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr8 | FileCheck %s -check-prefix=CHECK-SCO-HASQPX
 ; RUN: llc < %s -relocation-model=static -O1 -disable-ppc-sco=false -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 | FileCheck %s -check-prefix=CHECK-SCO-HASQPX
+; RUN: llc < %s -relocation-model=static -O1 -disable-ppc-sco=false -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 -code-model=small | FileCheck %s -check-prefix=SCM
 
 ; No combination of "powerpc64le-unknown-linux-gnu" + "CHECK-SCO", because
 ; only Power8 (and later) fully support LE.
@@ -142,7 +143,10 @@ define void @wo_hcaller(%class.T* %this, i8* %c) {
   ret void
 
 ; CHECK-SCO-LABEL: wo_hcaller:
-; CHECK-SCO: bl wo_hcallee
+; CHECK-SCO: b wo_hcallee
+
+; SCM-LABEL: wo_hcaller:
+; SCM:       bl wo_hcallee
 }
 
 define weak_odr protected void @wo_pcallee(%class.T* %this, i8* %c) { ret void }
@@ -151,7 +155,10 @@ define void @wo_pcaller(%class.T* %this, i8* %c) {
   ret void
 
 ; CHECK-SCO-LABEL: wo_pcaller:
-; CHECK-SCO: bl wo_pcallee
+; CHECK-SCO: b wo_pcallee
+
+; SCM-LABEL: wo_pcaller:
+; SCM:       bl wo_pcallee
 }
 
 define weak_odr void @wo_callee(%class.T* %this, i8* %c) { ret void }
@@ -160,7 +167,10 @@ define void @wo_caller(%class.T* %this, i8* %c) {
   ret void
 
 ; CHECK-SCO-LABEL: wo_caller:
-; CHECK-SCO: bl wo_callee
+; CHECK-SCO: b wo_callee
+
+; SCM-LABEL: wo_caller:
+; SCM:       bl wo_callee
 }
 
 define weak protected void @w_pcallee(i8* %ptr) { ret void }
@@ -169,7 +179,10 @@ define void @w_pcaller(i8* %ptr) {
   ret void
 
 ; CHECK-SCO-LABEL: w_pcaller:
-; CHECK-SCO: bl w_pcallee
+; CHECK-SCO: b w_pcallee
+
+; SCM-LABEL: w_pcaller:
+; SCM:       bl w_pcallee
 }
 
 define weak hidden void @w_hcallee(i8* %ptr) { ret void }
@@ -178,7 +191,10 @@ define void @w_hcaller(i8* %ptr) {
   ret void
 
 ; CHECK-SCO-LABEL: w_hcaller:
-; CHECK-SCO: bl w_hcallee
+; CHECK-SCO: b w_hcallee
+
+; SCM-LABEL: w_hcaller:
+; SCM:       bl w_hcallee
 }
 
 define weak void @w_callee(i8* %ptr) { ret void }
@@ -187,7 +203,10 @@ define void @w_caller(i8* %ptr) {
   ret void
 
 ; CHECK-SCO-LABEL: w_caller:
-; CHECK-SCO: bl w_callee
+; CHECK-SCO: b w_callee
+
+; SCM-LABEL: w_caller:
+; SCM:       bl w_callee
 }
 
 %struct.byvalTest = type { [8 x i8] }