[PATCH] D37775: Add a verifier test to check the access on both sides of COPY are the same

[Igor Breger via Phabricator via llvm-commits]

igorb added inline comments.


================
Comment at: lib/CodeGen/MachineVerifier.cpp:954
+        RegisterBankInfo::getSizeInBits(SrcOp.getReg(), *MRI, *TRI);
+    if (DstSize != SrcSize)
+      // Catch only obvious cases not involving subregs for now.
----------------
For X86  back-end this is not always correct.
I think in case a few register classes with different size are mapped to the same physical registers, it is impossible to identify when the COPY is illegal without some additional target specific info.
  def FR32 : RegisterClass<"X86", [f32], 32, (sequence "XMM%u", 0, 15)>;
  def VR128 : RegisterClass<"X86", [v4f32, v2f64, v16i8, v8i16, v4i32, v2i64], 128, (add FR32)>;

For example the test fail  DAG/GISEL (with the patch)
./bin/llc -O0 -mtriple=x86_64-linux-gnu -verify-machineinstrs -stop-before=legalizer
./bin/llc -O0 -mtriple=x86_64-linux-gnu -global-isel -verify-machineinstrs -stop-before=legalizer 

  define float @test_add_float(float %arg1, float %arg2) {
    %ret = fadd float %arg1, %arg2
    ret float %ret
  }

for the correct MIR.  (xmm size is 128)
    %0(s32) = COPY %xmm0
    %1(s32) = COPY %xmm1
    %2(s32) = G_FADD %0, %1
    %xmm0 = COPY %2(s32)

Thanks



Repository:
  rL LLVM

https://reviews.llvm.org/D37775