llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-llvm-selectiondag Author: Vitaly Buka (vitalybuka) <details> <summary>Changes</summary> --- Full diff: https://github.com/llvm/llvm-project/pull/84850.diff 4 Files Affected: - (modified) llvm/docs/LangRef.rst (+48) - (modified) llvm/include/llvm/IR/Intrinsics.td (+5) - (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (+6) - (added) llvm/test/CodeGen/Generic/builtin-hot.ll (+19) ``````````diff diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index d613ceea8654f8..36f4c964ee296c 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -27639,6 +27639,54 @@ constant `true`. However it is always correct to replace it with any other `i1` value. Any pass can freely do it if it can benefit from non-default lowering. +'``llvm.experimental.hot``' Intrinsic +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Syntax: +""""""" + +:: + + declare i1 @llvm.experimental.hot() + +Overview: +""""""""" + +This intrinsic returns true iff it's known that containing basic block is hot in +profile. + +When used with profile based optimization allows to change program behaviour +deppending on the code hotness. + +Arguments: +"""""""""" + +None. + +Semantics: +"""""""""" + +The intrinsic ``@llvm.experimental.hot()`` returns either `true` or `false`, +deppending on profile used. Expresion is evaluated as `true` iff profile and +summary are availible and profile counter for the block reach hotness threshold. +For each evaluation of a call to this intrinsic, the program must be valid and +correct both if it returns `true` and if it returns `false`. + +When used in a branch condition, it allows us to choose between +two alternative correct solutions for the same problem, like +in example below: + +.. code-block:: text + + %cond = call i1 @llvm.experimental.hot() + br i1 %cond, label %fast_path, label %slow_path + + label %fast_path: + ; Omit diagnostics. + + label %slow_path: + ; Additional diagnostics. + '``llvm.load.relative``' Intrinsic ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td index 144298fd7c0162..96e9cdf6627a75 100644 --- a/llvm/include/llvm/IR/Intrinsics.td +++ b/llvm/include/llvm/IR/Intrinsics.td @@ -1722,6 +1722,11 @@ def int_debugtrap : Intrinsic<[]>, def int_ubsantrap : Intrinsic<[], [llvm_i8_ty], [IntrNoReturn, IntrCold, ImmArg<ArgIndex<0>>]>; +// Return true if profile counter for containing block is hot. +def int_experimental_hot : Intrinsic<[llvm_i1_ty], [], + [IntrInaccessibleMemOnly, IntrWriteMem, + IntrWillReturn, NoUndef<RetIndex>]>; + // Support for dynamic deoptimization (or de-specialization) def int_experimental_deoptimize : Intrinsic<[llvm_any_ty], [llvm_vararg_ty], [Throws]>; diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index 22e57d0d99e9b1..8e73433ce82ea5 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -7276,6 +7276,12 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, setValue(&I, getValue(I.getArgOperand(0))); return; + case Intrinsic::experimental_hot: + // Default lowering to false. It's intended to be lowered as soon as profile + // is avalible to unblock other optimizations. + setValue(&I, DAG.getConstant(0, sdl, MVT::i1)); + return; + case Intrinsic::ubsantrap: case Intrinsic::debugtrap: case Intrinsic::trap: { diff --git a/llvm/test/CodeGen/Generic/builtin-hot.ll b/llvm/test/CodeGen/Generic/builtin-hot.ll new file mode 100644 index 00000000000000..449f58d3c00675 --- /dev/null +++ b/llvm/test/CodeGen/Generic/builtin-hot.ll @@ -0,0 +1,19 @@ +; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4 +; RUN: llc -o - %s | FileCheck %s + +; REQUIRES: aarch64-registered-target + +target triple = "aarch64-linux" + +define i1 @test() { +; CHECK-LABEL: test: +; CHECK: // %bb.0: // %entry +; CHECK-NEXT: mov w0, wzr +; CHECK-NEXT: ret +entry: + %hot = call i1 @llvm.experimental.hot() + ret i1 %hot +} + +declare i1 @llvm.expect.hot() nounwind + `````````` </details> https://github.com/llvm/llvm-project/pull/84850 _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
