[PowerPC][PCRelative] Set TLS unsupported with PC relative memops

Introduce a fatal error if any thread local storage code is compiled
using pc relative memory operations as well as a hidden override
option `-enable-ppc-pcrel-tls` so that this support can be incrementally
added if possible.

Reviewed By: #powerpc, nemanjai

Differential Revision: https://reviews.llvm.org/D85448

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -121,6 +121,11 @@ cl::desc("don't always align innermost loop to 32 bytes on ppc"), cl::Hidden);
 static cl::opt<bool> UseAbsoluteJumpTables("ppc-use-absolute-jumptables",
 cl::desc("use absolute jump tables on ppc"), cl::Hidden);
 
+static cl::opt<bool> EnablePPCPCRelTLS(
+    "enable-ppc-pcrel-tls",
+    cl::desc("enable the use of PC relative memops in TLS instructions on PPC"),
+    cl::Hidden);
+
 STATISTIC(NumTailCalls, "Number of tail calls");
 STATISTIC(NumSiblingCalls, "Number of sibling calls");
 STATISTIC(ShufflesHandledWithVPERM, "Number of shuffles lowered to a VPERM");
@@ -2920,6 +2925,9 @@ SDValue PPCTargetLowering::LowerGlobalTLSAddress(SDValue Op,
   // which is the most useful form.  Eventually support for small and
   // large models could be added if users need it, at the cost of
   // additional complexity.
+  if (Subtarget.isUsingPCRelativeCalls() && !EnablePPCPCRelTLS)
+    report_fatal_error("Thread local storage is not supported with pc-relative"
+                       " addressing - please compile with -mno-pcrel");
   GlobalAddressSDNode *GA = cast<GlobalAddressSDNode>(Op);
   if (DAG.getTarget().useEmulatedTLS())
     return LowerToTLSEmulatedModel(GA, DAG);

llvm/test/CodeGen/PowerPC/pcrel-tls.ll

@@ -0,0 +1,16 @@
+; RUN: not --crash llc -mcpu=pwr10 -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN:   -verify-machineinstrs -mattr=+pcrelative-memops -o - < %s 2>&1 | \
+; RUN:   FileCheck %s --check-prefix=CHECK-PCREL
+; RUN: llc -mcpu=pwr10 -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN:   -verify-machineinstrs -mattr=-pcrelative-memops -o - < %s 2>&1 | \
+; RUN:   FileCheck %s --check-prefix=CHECK-NOPCREL
+
+; CHECK-PCREL:     Thread local storage is not supported with pc-relative addressing
+; CHECK-NOPCREL:   blr
+
+@x = external thread_local global i32, align 4
+
+define i32* @testTLS() {
+entry:
+  ret i32* @x
+}