[PowerPC] Option for enabling absolute jumptables with command line

This option allows the user to specify the use of absolute jumptables instead
of relative which is the default on most PPC subtargets.

Patch by Kamauu Bridgeman

Differential revision: https://reviews.llvm.org/D69108

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 87ba74cf860..a2ffe9e3540 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -119,6 +119,9 @@ cl::desc("don't always align innermost loop to 32 bytes on ppc"), cl::Hidden);
 static cl::opt<bool> EnableQuadPrecision("enable-ppc-quad-precision",
 cl::desc("enable quad precision float support on ppc"), cl::Hidden);
 
+static cl::opt<bool> UseAbsoluteJumpTables("ppc-use-absolute-jumptables",
+cl::desc("use absolute jump tables on ppc"), cl::Hidden);
+
 STATISTIC(NumTailCalls, "Number of tail calls");
 STATISTIC(NumSiblingCalls, "Number of sibling calls");
 
@@ -2744,6 +2747,8 @@ unsigned PPCTargetLowering::getJumpTableEncoding() const {
 }
 
 bool PPCTargetLowering::isJumpTableRelative() const {
+  if (UseAbsoluteJumpTables)
+    return false;
   if (Subtarget.isPPC64())
     return true;
   return TargetLowering::isJumpTableRelative();