[llvm-branch-commits] [llvm] ARM: Remove remaining half convert libcall config into tablegen (PR #153408)

[Matt Arsenault via llvm-branch-commits]

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

>From 333abd7a754ece4bbf213ae17b43f094268b41d5 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 | 28 ++++++++++++++++++++-----
 llvm/lib/IR/RuntimeLibcalls.cpp         | 19 -----------------
 2 files changed, 23 insertions(+), 24 deletions(-)

diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.td b/llvm/include/llvm/IR/RuntimeLibcalls.td
index 04de19e257c9b..d6a3a8ccdb6e4 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.td
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.td
@@ -1491,10 +1491,17 @@ def ARMHalfConvertLibcallCallingConv : LibcallCallingConv<
     (isAAPCS_ABI(TT, ABIName) ? CallingConv::ARM_AAPCS : CallingConv::ARM_APCS)}]
 >;
 
-def GNUEABIHalfConvertCalls :
-  LibcallImpls<(add __gnu_f2h_ieee, __gnu_h2f_ieee),
-    RuntimeLibcallPredicate<[{!TT.isOSBinFormatMachO() &&
-                              !TT.isTargetAEABI()}]>> {
+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;
 }
 
@@ -1505,6 +1512,13 @@ def EABIHalfConvertCalls : LibcallImpls<(add __aeabi_f2h, __aeabi_h2f),
   let CallingConv = ARM_AAPCS;
 }
 
+def GNUEABIHalfConvertCalls :
+  LibcallImpls<(add __gnu_f2h_ieee, __gnu_h2f_ieee),
+    RuntimeLibcallPredicate<[{!TT.isOSBinFormatMachO() &&
+                              !TT.isTargetAEABI()}]>> {
+  let CallingConv = ARMHalfConvertLibcallCallingConv;
+}
+
 def WindowARMDivRemCalls : LibcallImpls<
   (add __rt_sdiv, __rt_sdiv64, __rt_udiv, __rt_udiv64),
   isOSWindows> {
@@ -1624,7 +1638,9 @@ 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,
@@ -1638,8 +1654,10 @@ 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 ac845c4998783..83f7df5e9f587 100644
--- a/llvm/lib/IR/RuntimeLibcalls.cpp
+++ b/llvm/lib/IR/RuntimeLibcalls.cpp
@@ -33,25 +33,6 @@ void RuntimeLibcallsInfo::initLibcalls(const Triple &TT,
   if (ExceptionModel == ExceptionHandling::SjLj)
     setLibcallImpl(RTLIB::UNWIND_RESUME, RTLIB::_Unwind_SjLj_Resume);
 
-  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;
-  }
-
   if (TT.getArch() == Triple::ArchType::msp430) {
     setLibcallImplCallingConv(RTLIB::__mspabi_mpyll,
                               CallingConv::MSP430_BUILTIN);