[PPCAsmPrinter] support 'L' output template for memory operands

Summary:
L is meant to support the second word used by 32b calling conventions for 64b arguments.

This is required for build 32b PowerPC Linux kernels after upstream
commit 334710b1496a ("powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'")

Thanks for the report from @nathanchance, and reference to GCC's
implementation from @segher.

Fixes: pr/46186
Fixes: https://github.com/ClangBuiltLinux/linux/issues/1044

Reviewers: echristo, hfinkel, MaskRay

Reviewed By: MaskRay

Subscribers: MaskRay, wuzish, nemanjai, hiraditya, kbarton, steven.zhang, llvm-commits, segher, nathanchance, srhines

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81767

(cherry picked from commit 2d8e105db6bea10a6b96e4a094e73a87987ef909)

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index 4311df5dbeb..20c5ac7b378 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -298,6 +298,11 @@ bool PPCAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
 
     switch (ExtraCode[0]) {
     default: return true;  // Unknown modifier.
+    case 'L': // A memory reference to the upper word of a double word op.
+      O << getDataLayout().getPointerSize() << "(";
+      printOperand(MI, OpNo, O);
+      O << ")";
+      return false;
     case 'y': // A memory reference for an X-form instruction
       {
         const char *RegName = "r0";
@@ -309,7 +314,6 @@ bool PPCAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
       }
     case 'U': // Print 'u' for update form.
     case 'X': // Print 'x' for indexed form.
-    {
       // FIXME: Currently for PowerPC memory operands are always loaded
       // into a register, so we never get an update or indexed form.
       // This is bad even for offset forms, since even if we know we
@@ -319,7 +323,6 @@ bool PPCAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
       assert(MI->getOperand(OpNo).isReg());
       return false;
     }
-    }
   }
 
   assert(MI->getOperand(OpNo).isReg());