[llvm] ca01779 - [APFloat][NFC] Add unit test coverage for `getArbitraryFPSemantics` (#216501)

[via llvm-commits]

Author: Chinmay Deshpande
Date: 2026-08-15T16:52:42-07:00
New Revision: ca017792fb043d24b683997a2d80eb79f933d14d

URL: https://github.com/llvm/llvm-project/commit/ca017792fb043d24b683997a2d80eb79f933d14d
DIFF: https://github.com/llvm/llvm-project/commit/ca017792fb043d24b683997a2d80eb79f933d14d.diff

LOG: [APFloat][NFC] Add unit test coverage for `getArbitraryFPSemantics` (#216501)

`isValidArbitraryFPFormat` and `getArbitraryFPFormatSizeInBits` have
unit tests, but `getArbitraryFPSemantics`, the mapping the conversion
intrinsics actually lower through, had none. Cover the formats it
supports, the valid formats it does not support yet, and invalid format
strings, and check that the two tables agree on the size of every format
with lowerable semantics.

Also add the missing Float8E5M3FNU case to the
`getArbitraryFPFormatSizeInBits` test.

Added: 
    

Modified: 
    llvm/unittests/ADT/APFloatTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 4ef2814e1a7b3..0c5103c4b49e4 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -10765,6 +10765,7 @@ TEST(APFloatTest, getArbitraryFPFormatSizeInBits) {
   EXPECT_EQ(8u, APFloat::getArbitraryFPFormatSizeInBits("Float8E4M3B11FNUZ"));
   EXPECT_EQ(8u, APFloat::getArbitraryFPFormatSizeInBits("Float8E3M4"));
   EXPECT_EQ(8u, APFloat::getArbitraryFPFormatSizeInBits("Float8E8M0FNU"));
+  EXPECT_EQ(8u, APFloat::getArbitraryFPFormatSizeInBits("Float8E5M3FNU"));
   EXPECT_EQ(6u, APFloat::getArbitraryFPFormatSizeInBits("Float6E3M2FN"));
   EXPECT_EQ(6u, APFloat::getArbitraryFPFormatSizeInBits("Float6E2M3FN"));
   EXPECT_EQ(4u, APFloat::getArbitraryFPFormatSizeInBits("Float4E2M1FN"));
@@ -10776,6 +10777,50 @@ TEST(APFloatTest, getArbitraryFPFormatSizeInBits) {
   EXPECT_EQ(0u, APFloat::getArbitraryFPFormatSizeInBits("unknown"));
 }
 
+TEST(APFloatTest, getArbitraryFPSemantics) {
+  // Formats that can currently be lowered map to their semantics.
+  EXPECT_EQ(&APFloat::Float8E5M2(),
+            APFloat::getArbitraryFPSemantics("Float8E5M2"));
+  EXPECT_EQ(&APFloat::Float8E4M3FN(),
+            APFloat::getArbitraryFPSemantics("Float8E4M3FN"));
+  EXPECT_EQ(&APFloat::Float6E3M2FN(),
+            APFloat::getArbitraryFPSemantics("Float6E3M2FN"));
+  EXPECT_EQ(&APFloat::Float6E2M3FN(),
+            APFloat::getArbitraryFPSemantics("Float6E2M3FN"));
+  EXPECT_EQ(&APFloat::Float4E2M1FN(),
+            APFloat::getArbitraryFPSemantics("Float4E2M1FN"));
+
+  // Formats that are valid but cannot be lowered yet report no semantics.
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E5M2FNUZ"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E4M3"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E4M3FNUZ"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E4M3B11FNUZ"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E3M4"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E8M0FNU"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8E5M3FNU"));
+
+  // Invalid formats report no semantics.
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics(""));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("Float8"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("float8e5m2"));
+  EXPECT_EQ(nullptr, APFloat::getArbitraryFPSemantics("unknown"));
+}
+
+// The two arbitrary FP format tables must agree: every format with lowerable
+// semantics reports the size of those semantics.
+TEST(APFloatTest, ArbitraryFPSemanticsMatchSizeInBits) {
+  for (StringRef Format :
+       {"Float8E5M2", "Float8E5M2FNUZ", "Float8E4M3", "Float8E4M3FN",
+        "Float8E4M3FNUZ", "Float8E4M3B11FNUZ", "Float8E3M4", "Float8E8M0FNU",
+        "Float8E5M3FNU", "Float6E3M2FN", "Float6E2M3FN", "Float4E2M1FN"}) {
+    ASSERT_TRUE(APFloat::isValidArbitraryFPFormat(Format)) << Format;
+    if (const fltSemantics *Sem = APFloat::getArbitraryFPSemantics(Format))
+      EXPECT_EQ(APFloat::getSizeInBits(*Sem),
+                APFloat::getArbitraryFPFormatSizeInBits(Format))
+          << Format;
+  }
+}
+
 TEST(APFloatTest, DecimalStringPreservesInexactStatus) {
   APFloat F(APFloat::IEEEsingle());