[llvm] [X86][BF16] Add libcall for F80 -> BF16 (PR #109116)
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Wed Sep 18 02:45:55 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-x86
Author: Phoebe Wang (phoebewang)
<details>
<summary>Changes</summary>
This fixes #<!-- -->108936, but the calling convention doesn't match with GCC. I doubt we have such a lib function for now, so leave the calling convention as is.
---
Full diff: https://github.com/llvm/llvm-project/pull/109116.diff
3 Files Affected:
- (modified) llvm/include/llvm/IR/RuntimeLibcalls.def (+1)
- (modified) llvm/lib/CodeGen/TargetLoweringBase.cpp (+2)
- (modified) llvm/test/CodeGen/X86/bfloat.ll (+22)
``````````diff
diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.def b/llvm/include/llvm/IR/RuntimeLibcalls.def
index c3d5ef9f4e4f82..69cf43140ad4bd 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.def
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.def
@@ -367,6 +367,7 @@ HANDLE_LIBCALL(FPROUND_F128_F16, "__trunctfhf2")
HANDLE_LIBCALL(FPROUND_PPCF128_F16, "__trunctfhf2")
HANDLE_LIBCALL(FPROUND_F32_BF16, "__truncsfbf2")
HANDLE_LIBCALL(FPROUND_F64_BF16, "__truncdfbf2")
+HANDLE_LIBCALL(FPROUND_F80_BF16, "__truncxfbf2")
HANDLE_LIBCALL(FPROUND_F64_F32, "__truncdfsf2")
HANDLE_LIBCALL(FPROUND_F80_F32, "__truncxfsf2")
HANDLE_LIBCALL(FPROUND_F128_F32, "__trunctfsf2")
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index eb3190c7cd247a..9fdde454559171 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -169,6 +169,8 @@ RTLIB::Libcall RTLIB::getFPROUND(EVT OpVT, EVT RetVT) {
return FPROUND_F32_BF16;
if (OpVT == MVT::f64)
return FPROUND_F64_BF16;
+ if (OpVT == MVT::f80)
+ return FPROUND_F80_BF16;
} else if (RetVT == MVT::f32) {
if (OpVT == MVT::f64)
return FPROUND_F64_F32;
diff --git a/llvm/test/CodeGen/X86/bfloat.ll b/llvm/test/CodeGen/X86/bfloat.ll
index 3759909a2ccc8e..3144fd56d9ccf3 100644
--- a/llvm/test/CodeGen/X86/bfloat.ll
+++ b/llvm/test/CodeGen/X86/bfloat.ll
@@ -1953,3 +1953,25 @@ define void @PR92471(ptr %0, ptr %1) nounwind {
store <7 x float> %4, ptr %1, align 4
ret void
}
+
+define bfloat @PR108936(x86_fp80 %0) nounwind {
+; X86-LABEL: PR108936:
+; X86: # %bb.0:
+; X86-NEXT: subl $12, %esp
+; X86-NEXT: fldt {{[0-9]+}}(%esp)
+; X86-NEXT: fstpt (%esp)
+; X86-NEXT: calll __truncxfbf2
+; X86-NEXT: addl $12, %esp
+; X86-NEXT: retl
+;
+; CHECK-LABEL: PR108936:
+; CHECK: # %bb.0:
+; CHECK-NEXT: subq $24, %rsp
+; CHECK-NEXT: fldt {{[0-9]+}}(%rsp)
+; CHECK-NEXT: fstpt (%rsp)
+; CHECK-NEXT: callq __truncxfbf2 at PLT
+; CHECK-NEXT: addq $24, %rsp
+; CHECK-NEXT: retq
+ %2 = fptrunc x86_fp80 %0 to bfloat
+ ret bfloat %2
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/109116
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