Fix infinite loop after r331115

There are two separate fixes here:
* The lowering code for non-extending loads should report UnableToLegalize instead of emitting the same instruction.
* The target should not be requesting lowering of non-extending loads.

llvm-svn: 331201

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index e4e5e0c6022..b1e7943462c 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1042,6 +1042,10 @@ LegalizerHelper::lower(MachineInstr &MI, unsigned TypeIdx, LLT Ty) {
     auto &MMO = **MI.memoperands_begin();
 
     if (DstTy.getSizeInBits() == MMO.getSize() /* in bytes */ * 8) {
+      // In the case of G_LOAD, this was a non-extending load already and we're
+      // about to lower to the same instruction.
+      if (MI.getOpcode() == TargetOpcode::G_LOAD)
+          return UnableToLegalize;
       MIRBuilder.buildLoad(DstReg, PtrReg, MMO);
       MI.eraseFromParent();
       return Legalized;