[PATCH] D86878: [AMDGPU] Fix a miscompile with S_ADD/S_SUB

Mon Oct 12 02:14:06 PDT 2020

foad added inline comments.

================
Comment at: llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp:1056
+    unsigned CondOpc = CI->getOpcode();
+    if (CI->getValueType(0) == MVT::i1 && CondOpc != ISD::SETCC &&
+        CondOpc != AMDGPUISD::FP_CLASS) {
----------------
In future it would be nice to improve this to detect a tree of SETCCs connected by ANDs and ORs. This kind of pattern seems to occur quite frequently:
```
        v_cmp_ne_u32_e64 s29, s29, 1
        v_cmp_ne_u32_e64 s0, s0, 0
        s_and_b32 s0, s0, s29
+       s_and_b32 s0, exec_lo, s0
```
where your patch has added the last AND instruction.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86878/new/

https://reviews.llvm.org/D86878