[PATCH] D49829: [X86] Add pattern matching for PMADDUBSW

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel, zvi.
craig.topper edited the summary of this revision.

Similar to https://reviews.llvm.org/D49636, but for PMADDUBSW. This instruction has the additional complexity that the addition of the two products saturates to 16-bits rather than wrapping around. And one operand is treated as signed and the other as unsigned.

I changed the madd.ll test command line from sse2 to ssse3 to ensure this instruction was available which also caused some test changes for phadd. I can commit that separately if desired. Or I can add a new run line. Or a new test file. Whatever is preferable

A C example that triggers this pattern

  static const int N = 128;
  
  int8_t A[2*N];
  uint8_t B[2*N];
  int16_t C[N];
  
  #define MIN(x, y) ((x) < (y)) ? (x) : (y)
  #define MAX(x, y) ((x) > (y)) ? (x) : (y)
  
  void foo() {
    for (int i = 0; i != N; ++i)
      C[i] = MIN(MAX((int16_t)A[2*i]*(int16_t)B[2*i] + (int16_t)A[2*i+1]*(int16_t)B[2*i+1], -32768), 32767);
  }


https://reviews.llvm.org/D49829

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/madd.ll

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