[ARM] GlobalISel: Fix extended stack operands

Fix a crash when trying to extend a value passed as a sign- or
zero-extended stack parameter. The cause of the crash was that we were
setting the size of the loaded value to 32 bits, and then tyring to
extend again to 32 bits.

This patch addresses the issue by also introducing a G_TRUNC after the
load. This will leave the unused bits to their original values set by
the caller, while being consistent about the types. For values that are
not extended, we just use a smaller load.

llvm-svn: 301531

1 files changed, 12 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM/ARMCallLowering.cpp b/llvm/lib/Target/ARM/ARMCallLowering.cpp
index 13fb30767c9..a8188411bf5 100644
--- a/llvm/lib/Target/ARM/ARMCallLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMCallLowering.cpp
@@ -245,12 +245,21 @@ struct IncomingValueHandler : public CallLowering::ValueHandler {
       // that's what we should load.
       Size = 4;
       assert(MRI.getType(ValVReg).isScalar() && "Only scalars supported atm");
-      MRI.setType(ValVReg, LLT::scalar(32));
+
+      auto LoadVReg = MRI.createGenericVirtualRegister(LLT::scalar(32));
+      buildLoad(LoadVReg, Addr, Size, /* Alignment */ 0, MPO);
+      MIRBuilder.buildTrunc(ValVReg, LoadVReg);
+    } else {
+      // If the value is not extended, a simple load will suffice.
+      buildLoad(ValVReg, Addr, Size, /* Alignment */ 0, MPO);
     }
+  }
 
+  void buildLoad(unsigned Val, unsigned Addr, uint64_t Size, unsigned Alignment,
+                 MachinePointerInfo &MPO) {
     auto MMO = MIRBuilder.getMF().getMachineMemOperand(
-        MPO, MachineMemOperand::MOLoad, Size, /* Alignment */ 0);
-    MIRBuilder.buildLoad(ValVReg, Addr, *MMO);
+        MPO, MachineMemOperand::MOLoad, Size, Alignment);
+    MIRBuilder.buildLoad(Val, Addr, *MMO);
   }
 
   void assignValueToReg(unsigned ValVReg, unsigned PhysReg,