[PATCH] D149401: [Clang][RISCV] Set native half type to legal when has zfh extension

[Yunze Zhu(Thead) via Phabricator via cfe-commits]

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Issue: When processing a f16 type value, a f16 value is extended to f32 after load and processed in f32 form, and truncated back to f16 before store, even when the target has zfh extension, which indicates the target has native half type float support, and such kind of extend/truncate actions are not necessary.

Some changes:
1.Set native half type to legal when has zfh extension, which prevent unnecessary promotion from f16 to f32, and unpromotion back to f16.
2.Add related test case to test generation of half type float.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149401

Files:
  clang/lib/Basic/Targets/RISCV.cpp
  clang/test/CodeGen/RISCV/_Float16-add.c


Index: clang/test/CodeGen/RISCV/_Float16-add.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/RISCV/_Float16-add.c
@@ -0,0 +1,19 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -triple riscv64 -target-feature +zfh -emit-llvm %s -o - \
+// RUN:   | FileCheck %s
+
+_Float16 x;
+_Float16 y;
+_Float16 z;
+// CHECK-LABEL: @func(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = load half, ptr @y, align 2
+// CHECK-NEXT:    [[TMP1:%.*]] = load half, ptr @z, align 2
+// CHECK-NEXT:    [[ADD:%.*]] = fadd half [[TMP0]], [[TMP1]]
+// CHECK-NEXT:    store half [[ADD]], ptr @x, align 2
+// CHECK-NEXT:    ret void
+//
+void func()
+{
+  x = y + z;
+}
Index: clang/lib/Basic/Targets/RISCV.cpp
===================================================================
--- clang/lib/Basic/Targets/RISCV.cpp
+++ clang/lib/Basic/Targets/RISCV.cpp
@@ -349,6 +349,11 @@
     ISAInfo = std::move(*ParseResult);
   }
 
+  // Turn on native half type support by set half type to legal.
+  if (ISAInfo->hasExtension("zfh")){
+    HasLegalHalfType = true;
+  }
+
   if (ABI.empty())
     ABI = ISAInfo->computeDefaultABI().str();
 


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