commit b074a608ceb2514ff5c8967b0f36c168fb54576e
author Hal Finkel <hfinkel@anl.gov> Tue Aug 30 00:59:23 2016 +0000
committer Hal Finkel <hfinkel@anl.gov> Tue Aug 30 00:59:23 2016 +0000
tree f34276831928cad569fd5763ac8d398a78a8fc32
parent 455d3569d84c0e999257b7e7b87b9b7e46dd8774

[PowerPC] Add support for -mlongcall

The "long call" option forces the use of the indirect calling sequence for all
calls (even those that don't really need it). GCC provides this option; This is
helpful, under certain circumstances, for building very-large binaries, and
some other specialized use cases.

Fixes PR19098.

llvm-svn: 280040

llvm/lib/Target/PowerPC/PPC.td

diff --git a/llvm/lib/Target/PowerPC/PPC.td b/llvm/lib/Target/PowerPC/PPC.td
index b40b530..ac1c306 100644
--- a/llvm/lib/Target/PowerPC/PPC.td
+++ b/llvm/lib/Target/PowerPC/PPC.td
@@ -136,6 +136,8 @@
   SubtargetFeature<"invariant-function-descriptors",
                    "HasInvariantFunctionDescriptors", "true",
                    "Assume function descriptors are invariant">;
+def FeatureLongCall : SubtargetFeature<"longcall", "UseLongCalls", "true",
+                                       "Always use indirect calls">;
 def FeatureHTM : SubtargetFeature<"htm", "HasHTM", "true",
                                   "Enable Hardware Transactional Memory instructions">;
 def FeatureMFTB   : SubtargetFeature<"", "FeatureMFTB", "true",

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index f895b06..09887c3 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -4695,7 +4695,9 @@
   ImmutableCallSite *CS                 = CLI.CS;
 
   if (isTailCall) {
-    if (Subtarget.isSVR4ABI() && Subtarget.isPPC64())
+    if (Subtarget.useLongCalls() && !(CS && CS->isMustTailCall()))
+      isTailCall = false;
+    else if (Subtarget.isSVR4ABI() && Subtarget.isPPC64())
       isTailCall =
         IsEligibleForTailCallOptimization_64SVR4(Callee, CallConv, CS,
                                                  isVarArg, Outs, Ins, DAG);
@@ -4725,6 +4727,13 @@
     report_fatal_error("failed to perform tail call elimination on a call "
                        "site marked musttail");
 
+  // When long calls (i.e. indirect calls) are always used, calls are always
+  // made via function pointer. If we have a function name, first translate it
+  // into a pointer.
+  if (Subtarget.useLongCalls() && isa<GlobalAddressSDNode>(Callee) &&
+      !isTailCall)
+    Callee = LowerGlobalAddress(Callee, DAG);
+
   if (Subtarget.isSVR4ABI()) {
     if (Subtarget.isPPC64())
       return LowerCall_64SVR4(Chain, Callee, CallConv, isVarArg,

llvm/lib/Target/PowerPC/PPCSubtarget.cpp

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index 603f0fc..1957073 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -105,6 +105,7 @@
   HasFusion = false;
   HasFloat128 = false;
   IsISA3_0 = false;
+  UseLongCalls = false;
 
   HasPOPCNTD = POPCNTD_Unavailable;
 }

llvm/lib/Target/PowerPC/PPCSubtarget.h

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.h b/llvm/lib/Target/PowerPC/PPCSubtarget.h
index 9fe286a..f58c7c1 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.h
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.h
@@ -132,6 +132,7 @@
   bool HasFusion;
   bool HasFloat128;
   bool IsISA3_0;
+  bool UseLongCalls;
 
   POPCNTDKind HasPOPCNTD;
 
@@ -275,6 +276,7 @@
   bool hasFusion() const { return HasFusion; }
   bool hasFloat128() const { return HasFloat128; }
   bool isISA3_0() const { return IsISA3_0; }
+  bool useLongCalls() const { return UseLongCalls; }
 
   POPCNTDKind hasPOPCNTD() const { return HasPOPCNTD; }