[X86] Optimize umax(X,1) (NFC)

Without this patch:

  %cond = call i32 @llvm.umax.i32(i32 %X, i32 1)

is compiled as:

  83 ff 02                   cmp    $0x2,%edi
  b8 01 00 00 00             mov    $0x1,%eax
  0f 43 c7                   cmovae %edi,%eax

With this patch, the compiler generates:

  89 f8                      mov    %edi,%eax
  83 ff 01                   cmp    $0x1,%edi
  83 d0 00                   adc    $0x0,%eax

saving 3 bytes.  We should be able to save 5 bytes in larger functions
where the mov is unnecessary.

This patch converts the specific cmov pattern to cmp $1 followed by
adc $0.

This patch partially fixes:

https://github.com/llvm/llvm-project/issues/60374

The LLVM IR optimizer is yet to canonicalize max expressions to
actual @llvm.umax.

Differential Revision: https://reviews.llvm.org/D144451

0 files changed, 0 insertions, 0 deletions