[PATCH] D123109: [x86] improve select lowering for smin(x, 0) & smax(x, 0)

[Phoebe Wang via Phabricator via llvm-commits]

pengfei added inline comments.


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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:24784
+    } else if ((VT == MVT::i32 || VT == MVT::i64) && isNullConstant(Op2) &&
+        (CmpOp0 == Op1) && ((CondCode == X86::COND_S) ||    // smin(x, 0)
+            (CondCode == X86::COND_G && hasAndNot(Op1)))) { // smax(x, 0)
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clang-format


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Comment at: llvm/test/CodeGen/X86/fpclamptosat_vec.ll:2986-3006
+; CHECK-NEXT:    movq %rdx, %rsi
+; CHECK-NEXT:    sarq $63, %rsi
+; CHECK-NEXT:    andq %rdx, %rsi
+; CHECK-NEXT:    movq %r14, %rdx
+; CHECK-NEXT:    sarq $63, %rdx
+; CHECK-NEXT:    andq %r14, %rdx
 ; CHECK-NEXT:    movabsq $-9223372036854775808, %rbx # imm = 0x8000000000000000
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I see the right side has more instructions, is this still better in performance?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D123109/new/

https://reviews.llvm.org/D123109