[all-commits] [llvm/llvm-project] 5c91b9: [ARMISelLowering] avoid emitting libcalls to __mul...

[Nick Desaulniers via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5c91b98c5d45243352bf10262454bcac77cd3fed
      https://github.com/llvm/llvm-project/commit/5c91b98c5d45243352bf10262454bcac77cd3fed
  Author: Nick Desaulniers <ndesaulniers at google.com>
  Date:   2021-08-27 (Fri, 27 Aug 2021)

  Changed paths:
    M llvm/lib/Target/ARM/ARMISelLowering.cpp
    M llvm/test/CodeGen/ARM/overflow-intrinsic-optimizations.ll

  Log Message:
  -----------
  [ARMISelLowering] avoid emitting libcalls to __mulodi4()

__has_builtin(__builtin_mul_overflow) returns true for 32b ARM targets,
but Clang is deferring to compiler RT when encountering `long long`
types. This breaks sanitizer builds of the Linux kernel that are using
__builtin_mul_overflow with these types for these targets.

If the semantics of __has_builtin mean "the compiler resolves these,
always" then we shouldn't conditionally emit a libcall.

This will still need to be worked around in the Linux kernel in order to
continue to support allmodconfig builds of the Linux kernel for this
target with older releases of clang.

Link: https://bugs.llvm.org/show_bug.cgi?id=28629
Link: https://github.com/ClangBuiltLinux/linux/issues/1438

Reviewed By: rengolin

Differential Revision: https://reviews.llvm.org/D108842