From 66e3e52349751389cd61925e84ab64cdc6257dec Mon Sep 17 00:00:00 2001
From: Mike Smith <mango@live.cn>
Date: Mon, 13 Jan 2025 16:11:10 +0800
Subject: [PATCH] use fshl/fshr to implement bit rotate

---
 src/backends/fallback/fallback_codegen.cpp | 68 ++--------------------
 1 file changed, 4 insertions(+), 64 deletions(-)

diff --git a/src/backends/fallback/fallback_codegen.cpp b/src/backends/fallback/fallback_codegen.cpp
index 688324ee8..832326bf7 100644
--- a/src/backends/fallback/fallback_codegen.cpp
+++ b/src/backends/fallback/fallback_codegen.cpp
@@ -765,77 +765,17 @@ class FallbackCodegen {
     }
 
     [[nodiscard]] llvm::Value *_translate_binary_rotate_left(CurrentFunction &current, IRBuilder &b, const xir::Value *value, const xir::Value *shift) noexcept {
+        LUISA_ASSERT(value->type() == shift->type(), "Type mismatch for rotate left.");
         auto llvm_value = _lookup_value(current, b, value);
         auto llvm_shift = _lookup_value(current, b, shift);
-        auto value_type = value->type();
-        auto elem_type = value_type->is_vector() ? value_type->element() : value_type;
-        LUISA_ASSERT(value_type != nullptr, "Operand type is null.");
-        LUISA_ASSERT(value_type == shift->type(), "Type mismatch for rotate left.");
-        LUISA_ASSERT(value_type->is_scalar() || value_type->is_vector(), "Invalid operand type.");
-        auto bit_width = 0u;
-        switch (elem_type->tag()) {
-            case Type::Tag::INT8: [[fallthrough]];
-            case Type::Tag::UINT8: bit_width = 8; break;
-            case Type::Tag::INT16: [[fallthrough]];
-            case Type::Tag::UINT16: bit_width = 16; break;
-            case Type::Tag::INT32: [[fallthrough]];
-            case Type::Tag::UINT32: bit_width = 32; break;
-            case Type::Tag::INT64: [[fallthrough]];
-            case Type::Tag::UINT64: bit_width = 64; break;
-            default: LUISA_ERROR_WITH_LOCATION(
-                "Invalid operand type for rotate left operation: {}.",
-                elem_type->description());
-        }
-        auto llvm_elem_type = _translate_type(elem_type, true);
-        auto llvm_bit_width = llvm::ConstantInt::get(llvm_elem_type, bit_width);
-        if (value_type->is_vector()) {
-            llvm_bit_width = llvm::ConstantVector::getSplat(
-                llvm::ElementCount::getFixed(value_type->dimension()),
-                llvm_bit_width);
-        }
-        auto shifted_left = b.CreateShl(llvm_value, llvm_shift);
-        auto complement_shift = b.CreateSub(llvm_bit_width, llvm_shift);
-        auto shifted_right = b.CreateLShr(llvm_value, complement_shift);
-        return b.CreateOr(shifted_left, shifted_right);
+        return b.CreateIntrinsic(llvm_value->getType(), llvm::Intrinsic::fshl, {llvm_value, llvm_value, llvm_shift});
     }
 
     [[nodiscard]] llvm::Value *_translate_binary_rotate_right(CurrentFunction &current, IRBuilder &b, const xir::Value *value, const xir::Value *shift) noexcept {
-        // Lookup LLVM values for operands
+        LUISA_ASSERT(value->type() == shift->type(), "Type mismatch for rotate right.");
         auto llvm_value = _lookup_value(current, b, value);
         auto llvm_shift = _lookup_value(current, b, shift);
-        auto value_type = value->type();
-        auto elem_type = value_type->is_vector() ? value_type->element() : value_type;
-
-        // Type and null checks
-        LUISA_ASSERT(value_type != nullptr, "Operand type is null.");
-        LUISA_ASSERT(value_type == shift->type(), "Type mismatch for rotate right.");
-        LUISA_ASSERT(value_type->is_scalar() || value_type->is_vector(), "Invalid operand type.");
-
-        auto bit_width = 0u;
-        switch (elem_type->tag()) {
-            case Type::Tag::INT8: [[fallthrough]];
-            case Type::Tag::UINT8: bit_width = 8; break;
-            case Type::Tag::INT16: [[fallthrough]];
-            case Type::Tag::UINT16: bit_width = 16; break;
-            case Type::Tag::INT32: [[fallthrough]];
-            case Type::Tag::UINT32: bit_width = 32; break;
-            case Type::Tag::INT64: [[fallthrough]];
-            case Type::Tag::UINT64: bit_width = 64; break;
-            default: LUISA_ERROR_WITH_LOCATION(
-                "Invalid operand type for rotate right operation: {}.",
-                elem_type->description());
-        }
-        auto llvm_elem_type = _translate_type(elem_type, true);
-        auto llvm_bit_width = llvm::ConstantInt::get(llvm_elem_type, bit_width);
-        if (value_type->is_vector()) {
-            llvm_bit_width = llvm::ConstantVector::getSplat(
-                llvm::ElementCount::getFixed(value_type->dimension()),
-                llvm_bit_width);
-        }
-        auto shifted_right = b.CreateLShr(llvm_value, llvm_shift);
-        auto complement_shift = b.CreateSub(llvm_bit_width, llvm_shift);
-        auto shifted_left = b.CreateShl(llvm_value, complement_shift);
-        return b.CreateOr(shifted_left, shifted_right);
+        return b.CreateIntrinsic(llvm_value->getType(), llvm::Intrinsic::fshr, {llvm_value, llvm_value, llvm_shift});
     }
 
     [[nodiscard]] llvm::Value *_translate_binary_less(CurrentFunction &current, IRBuilder &b, const xir::Value *lhs, const xir::Value *rhs) noexcept {