[llvm] ARM: Move remaining half convert libcall config into tablegen (PR #153408)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/153408

>From 67eb146af0524b257569f268e0862c39144bb026 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 13 Aug 2025 21:05:36 +0900
Subject: [PATCH] ARM: Remove remaining half convert libcall config into
 tablegen

The __truncdfhf2 handling is kind of convoluted, but reproduces
the existing, likely wrong, handling.
---
 llvm/include/llvm/IR/RuntimeLibcalls.td | 34 +++++++++++++++++++------
 llvm/lib/IR/RuntimeLibcalls.cpp         | 19 --------------
 2 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.td b/llvm/include/llvm/IR/RuntimeLibcalls.td
index 1f596184f3d6a..a774a20d8d0d6 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.td
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.td
@@ -1576,13 +1576,6 @@ def __aeabi_h2f : RuntimeLibcallImpl<FPEXT_F16_F32>; // CallingConv::ARM_AAPCS
 def __gnu_f2h_ieee : RuntimeLibcallImpl<FPROUND_F32_F16>;
 def __gnu_h2f_ieee : RuntimeLibcallImpl<FPEXT_F16_F32>;
 
-// In EABI, these functions have an __aeabi_ prefix, but in GNUEABI
-// they have a __gnu_ prefix (which is the default).
-def EABIHalfConvertCalls : LibcallImpls<(add __aeabi_f2h, __aeabi_h2f),
-                                        isTargetAEABIAndAAPCS_ABI> {
-  let CallingConv = ARM_AAPCS;
-}
-
 // The half <-> float conversion functions are always soft-float on
 // non-watchos platforms, but are needed for some targets which use a
 // hard-float calling convention by default.
@@ -1591,6 +1584,27 @@ def ARMHalfConvertLibcallCallingConv : LibcallCallingConv<
     (isAAPCS_ABI(TT, ABIName) ? CallingConv::ARM_AAPCS : CallingConv::ARM_APCS)}]
 >;
 
+def ARMLibgccHalfConvertCalls :
+  LibcallImpls<(add __truncsfhf2, __extendhfsf2),
+    RuntimeLibcallPredicate<[{!TT.isTargetAEABI() && TT.isOSBinFormatMachO()}]>> {
+  let CallingConv = ARMHalfConvertLibcallCallingConv;
+}
+
+// FIXME: These conditions are probably bugged. We're using the
+// default libgcc call when the other cases are replaced.
+def ARMDoubleToHalfCalls :
+  LibcallImpls<(add __truncdfhf2),
+    RuntimeLibcallPredicate<[{!TT.isTargetAEABI()}]>> {
+  let CallingConv = ARMHalfConvertLibcallCallingConv;
+}
+
+// In EABI, these functions have an __aeabi_ prefix, but in GNUEABI
+// they have a __gnu_ prefix (which is the default).
+def EABIHalfConvertCalls : LibcallImpls<(add __aeabi_f2h, __aeabi_h2f),
+                                        isTargetAEABIAndAAPCS_ABI> {
+  let CallingConv = ARM_AAPCS;
+}
+
 def GNUEABIHalfConvertCalls :
   LibcallImpls<(add __gnu_f2h_ieee, __gnu_h2f_ieee),
     RuntimeLibcallPredicate<[{!TT.isOSBinFormatMachO() &&
@@ -1717,7 +1731,9 @@ def isARMOrThumb : RuntimeLibcallPredicate<"TT.isARM() || TT.isThumb()">;
 
 def ARMSystemLibrary
     : SystemRuntimeLibrary<isARMOrThumb,
-      (add WinDefaultLibcallImpls,
+      (add (sub WinDefaultLibcallImpls, ARMLibgccHalfConvertCalls,
+                                        GNUEABIHalfConvertCalls,
+                                        ARMDoubleToHalfCalls),
            LibcallImpls<(add __powisf2, __powidf2), isNotOSMSVCRT>,
            LibmHasFrexpF32, LibmHasLdexpF32,
            LibmHasFrexpF128, LibmHasLdexpF128,
@@ -1731,8 +1747,10 @@ def ARMSystemLibrary
 
            AEABICalls,
            AEABI45MemCalls,
+           ARMLibgccHalfConvertCalls,
            EABIHalfConvertCalls,
            GNUEABIHalfConvertCalls,
+           ARMDoubleToHalfCalls,
 
            // Use divmod compiler-rt calls for iOS 5.0 and later.
            LibcallImpls<(add __divmodsi4, __udivmodsi4),
diff --git a/llvm/lib/IR/RuntimeLibcalls.cpp b/llvm/lib/IR/RuntimeLibcalls.cpp
index 3c324f2fe0d84..7ea2e46a54183 100644
--- a/llvm/lib/IR/RuntimeLibcalls.cpp
+++ b/llvm/lib/IR/RuntimeLibcalls.cpp
@@ -33,25 +33,6 @@ void RuntimeLibcallsInfo::initLibcalls(const Triple &TT,
                                        EABI EABIVersion, StringRef ABIName) {
   setTargetRuntimeLibcallSets(TT, ExceptionModel, FloatABI, EABIVersion,
                               ABIName);
-
-  if (TT.isARM() || TT.isThumb()) {
-    // The half <-> float conversion functions are always soft-float on
-    // non-watchos platforms, but are needed for some targets which use a
-    // hard-float calling convention by default.
-    if (!TT.isWatchABI()) {
-      if (isAAPCS_ABI(TT, ABIName)) {
-        setLibcallImplCallingConv(RTLIB::__truncsfhf2, CallingConv::ARM_AAPCS);
-        setLibcallImplCallingConv(RTLIB::__truncdfhf2, CallingConv::ARM_AAPCS);
-        setLibcallImplCallingConv(RTLIB::__extendhfsf2, CallingConv::ARM_AAPCS);
-      } else {
-        setLibcallImplCallingConv(RTLIB::__truncsfhf2, CallingConv::ARM_APCS);
-        setLibcallImplCallingConv(RTLIB::__truncdfhf2, CallingConv::ARM_APCS);
-        setLibcallImplCallingConv(RTLIB::__extendhfsf2, CallingConv::ARM_APCS);
-      }
-    }
-
-    return;
-  }
 }
 
 LLVM_ATTRIBUTE_ALWAYS_INLINE