[all-commits] [llvm/llvm-project] 5e0be9: [PowerPC] Support PIC Secure PLT for CALL_RM

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5e0be962feb37b224590e91879f9ac4a1fcacb85
      https://github.com/llvm/llvm-project/commit/5e0be962feb37b224590e91879f9ac4a1fcacb85
  Author: Fangrui Song <i at maskray.me>
  Date:   2025-01-06 (Mon, 06 Jan 2025)

  Changed paths:
    M llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
    M llvm/test/CodeGen/PowerPC/ppc32-pic-large.ll

  Log Message:
  -----------
  [PowerPC] Support PIC Secure PLT for CALL_RM

https://reviews.llvm.org/D111433 introduced PPCISD::CALL_RM for
-frounding-math. -msecure-plt -frounding-math {-fpic,-fPIC} codegen for
PPC32 became incorrect when a function contains function calls but no
global variable references (GlobalBaseReg).

As reported by @q66 , musl/src/dirent/closedir.c implements such a
function, which is miscompiled.

PPCISD::CALL has custom logic to set up the base register
(https://reviews.llvm.org/D42112). Add an extra case for CALL_RM.

While here, improve the test to

* actually test `case PPCISD::CALL`: we need a non-leaf function that
  doesn't access global variables (global variables lead to
  GlobalBaseReg, which call `getGlobalBaseReg()` as well).
* test `ExternalSymbolSDNode` with a memset.

Supersedes: #72758

Pull Request: https://github.com/llvm/llvm-project/pull/121281



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