[202x] Add support for bit-precise float suffixes (#8478)

This updates the literal parser to handle bit-precise float suffixes for
16, 32, and 64-bit types. These changes reflect the latest updates to
the conforming literals proposal (PR:
hlsl-tc57/tc57#52).

Author: llvm-beanz

tools/clang/include/clang/Basic/DiagnosticGroups.td

@@ -808,4 +808,5 @@ def HLSLAvailabilityConstant: DiagGroup<"hlsl-availability-constant">;
 def HLSLBarrier : DiagGroup<"hlsl-barrier">;
 def HLSLLegacyLiterals : DiagGroup<"hlsl-legacy-literal">;
 def HLSLGroupshared202x : DiagGroup<"hlsl-groupshared-202x">;
+def HLSL202xExtensions : DiagGroup<"hlsl-202x-extensions", [HLSLGroupshared202x]>;
 // HLSL Change Ends

tools/clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -658,4 +658,12 @@ def err_pp_eof_in_assume_nonnull : Error<
 
 }
 
+// HLSL Change Begin - fixed-size floating-point literal suffixes
+def ext_hlsl_fixed_size_float_suffix_202x : ExtWarn<
+  "fixed-size floating-point literal suffix '%0' is a HLSL 202x extension">,
+  InGroup<HLSL202xExtensions>;
+def err_hlsl_16bit_suffix_requires_native_16bit : Error<
+  "16-bit floating-point literal suffix '%0' requires '-enable-16bit-types'">;
+// HLSL Change End
+
 }

tools/clang/lib/Lex/LiteralSupport.cpp

@@ -609,6 +609,42 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
     case 'F':
      if (!isFPConstant) break;  // Error for integer constant.
       if (isFloat || isLong) break; // FF, LF invalid.
+      // HLSL Change Begin - fixed-size float suffixes f16/f32/f64
+      if (PP.getLangOpts().HLSL && (s + 2) < ThisTokEnd) {
+        unsigned Width = 0;
+        if (s[1] == '1' && s[2] == '6')
+          Width = 16;
+        else if (s[1] == '3' && s[2] == '2')
+          Width = 32;
+        else if (s[1] == '6' && s[2] == '4')
+          Width = 64;
+        if (Width != 0) {
+          StringRef SuffixStr(s, 3);
+          if (PP.getLangOpts().HLSLVersion < hlsl::LangStd::v202x) {
+            PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, s - ThisTokBegin),
+                    diag::ext_hlsl_fixed_size_float_suffix_202x)
+                << SuffixStr;
+          }
+          if (Width == 16 && PP.getLangOpts().UseMinPrecision) {
+            PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, s - ThisTokBegin),
+                    diag::err_hlsl_16bit_suffix_requires_native_16bit)
+                << SuffixStr;
+            hadError = true;
+          }
+          // Reuse existing width flags: f16 acts like 'h' (half), f32 like
+          // 'f' (float), f64 like 'l' (double in HLSL). The source token is
+          // preserved if anything later needs to distinguish the spellings.
+          if (Width == 16)
+            isHalf = true;
+          else if (Width == 32)
+            isFloat = true;
+          else
+            isLong = true;
+          s += 2; // The outer loop's ++s consumes the leading 'f'/'F'.
+          continue;
+        }
+      }
+      // HLSL Change End
       isFloat = true;
       continue;  // Success.
 // HLSL Change Starts
@@ -718,6 +754,7 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
       isUnsigned = false;
       isLongLong = false;
       isFloat = false;
+      isHalf = false; // HLSL Change
       isImaginary = false;
       MicrosoftInteger = 0;
 

tools/clang/test/SemaHLSL/v202x/conforming-literals/fixed-size-float-suffixes-invalid.hlsl

@@ -0,0 +1,70 @@
+// RUN: %dxc -T lib_6_3 -HV 202x -enable-16bit-types -verify %s
+
+// Verify that float literal suffixes that look like fixed-size width
+// suffixes but specify an unsupported width are rejected. Only 16, 32 and
+// 64 are valid widths; everything else must produce an
+// "invalid suffix on floating constant" error.
+
+float plausible_f8() {
+  // 'f8' would be an 8-bit float, which we don't support.
+  // expected-error@+1{{invalid suffix 'f8' on floating constant}}
+  return 1.0f8;
+}
+
+float plausible_F8() {
+  // expected-error@+1{{invalid suffix 'F8' on floating constant}}
+  return 1.0F8;
+}
+
+float plausible_f128() {
+  // 'f128' would be a 128-bit float, which we don't support.
+  // expected-error@+1{{invalid suffix 'f128' on floating constant}}
+  return 1.0f128;
+}
+
+float plausible_F128() {
+  // expected-error@+1{{invalid suffix 'F128' on floating constant}}
+  return 1.0F128;
+}
+
+float implausible_f23() {
+  // 'f23' is not a meaningful width but the parser should still reject it.
+  // expected-error@+1{{invalid suffix 'f23' on floating constant}}
+  return 1.0f23;
+}
+
+float implausible_f7() {
+  // 'f7' is not a meaningful width but the parser should still reject it.
+  // expected-error@+1{{invalid suffix 'f7' on floating constant}}
+  return 1.0f7;
+}
+
+float implausible_f0() {
+  // expected-error@+1{{invalid suffix 'f0' on floating constant}}
+  return 1.0f0;
+}
+
+float implausible_f31() {
+  // One off from a valid width.
+  // expected-error@+1{{invalid suffix 'f31' on floating constant}}
+  return 1.0f31;
+}
+
+float implausible_f33() {
+  // expected-error@+1{{invalid suffix 'f33' on floating constant}}
+  return 1.0f33;
+}
+
+float trailing_garbage_after_valid_width() {
+  // A valid fixed-size suffix followed by extra characters is still an
+  // invalid suffix.
+  // expected-error@+1{{invalid suffix 'f32x' on floating constant}}
+  return 1.0f32x;
+}
+
+float trailing_number_after_valid_width() {
+  // A valid fixed-size suffix followed by an extra number is still an invalid
+  // suffix.
+  // expected-error@+1{{invalid suffix 'f324' on floating constant}}
+  return 1.0f324;
+}

tools/clang/test/SemaHLSL/v202x/conforming-literals/fixed-size-float-suffixes-legacy.hlsl

@@ -0,0 +1,49 @@
+// RUN: %dxc -T lib_6_3 -HV 2021 -verify %s
+
+// In HLSL 2021 and earlier, the fixed-size float suffixes f16/f32/f64 should
+// still work, but produce an extension warning. With -enable-16bit-types not
+// passed, the 16-bit suffix should also error.
+
+template <typename T, typename U>
+struct is_same {
+  static const bool value = false;
+};
+
+template <typename T>
+struct is_same<T, T> {
+  static const bool value = true;
+};
+
+float test_f32() {
+  // expected-warning@+1{{fixed-size floating-point literal suffix 'f32' is a HLSL 202x extension}}
+  return 1.0f32;
+}
+
+float test_F32() {
+  // expected-warning@+1{{fixed-size floating-point literal suffix 'F32' is a HLSL 202x extension}}
+  return 1.0F32;
+}
+
+double test_f64() {
+  // expected-warning@+1{{fixed-size floating-point literal suffix 'f64' is a HLSL 202x extension}}
+  return 1.0f64;
+}
+
+double test_F64() {
+  // expected-warning@+1{{fixed-size floating-point literal suffix 'F64' is a HLSL 202x extension}}
+  return 1.0F64;
+}
+
+// Without -enable-16bit-types the 16-bit suffix must error (in addition to the
+// extension warning).
+min16float test_f16() {
+  // expected-warning@+2{{fixed-size floating-point literal suffix 'f16' is a HLSL 202x extension}}
+  // expected-error@+1{{16-bit floating-point literal suffix 'f16' requires '-enable-16bit-types'}}
+  return 1.0f16;
+}
+
+min16float test_F16() {
+  // expected-warning@+2{{fixed-size floating-point literal suffix 'F16' is a HLSL 202x extension}}
+  // expected-error@+1{{16-bit floating-point literal suffix 'F16' requires '-enable-16bit-types'}}
+  return 1.0F16;
+}

tools/clang/test/SemaHLSL/v202x/conforming-literals/fixed-size-float-suffixes-no-native-16bit.hlsl

@@ -0,0 +1,22 @@
+// RUN: %dxc -T lib_6_3 -HV 202x -verify %s
+
+// In HLSL 202x mode without -enable-16bit-types, the 16-bit suffix must error
+// while f32/f64 are accepted silently.
+
+float test_f32() {
+  return 1.0f32; // no diagnostic
+}
+
+double test_f64() {
+  return 1.0f64; // no diagnostic
+}
+
+min16float test_f16() {
+  // expected-error@+1{{16-bit floating-point literal suffix 'f16' requires '-enable-16bit-types'}}
+  return 1.0f16;
+}
+
+min16float test_F16() {
+  // expected-error@+1{{16-bit floating-point literal suffix 'F16' requires '-enable-16bit-types'}}
+  return 1.0F16;
+}

tools/clang/test/SemaHLSL/v202x/conforming-literals/fixed-size-float-suffixes.hlsl

@@ -0,0 +1,39 @@
+// RUN: %dxc -T lib_6_3 -HV 202x -enable-16bit-types -verify %s
+
+// Verify that f16/F16/f32/F32/f64/F64 produce the expected types in HLSL 202x
+// with native 16-bit types enabled.
+
+template <typename T, typename U>
+struct is_same {
+  static const bool value = false;
+};
+
+template <typename T>
+struct is_same<T, T> {
+  static const bool value = true;
+};
+
+// expected-no-diagnostics
+
+// 16-bit suffix -> float16_t (a.k.a. half / HalfTy).
+_Static_assert(is_same<__decltype(1.0f16), half>::value, "1.0f16 is half");
+_Static_assert(is_same<__decltype(1.0F16), half>::value, "1.0F16 is half");
+_Static_assert(is_same<__decltype(2.5e1f16), half>::value, "2.5e1f16 is half");
+
+// 32-bit suffix -> float, regardless of UseMinPrecision.
+_Static_assert(is_same<__decltype(1.0f32), float>::value, "1.0f32 is float");
+_Static_assert(is_same<__decltype(1.0F32), float>::value, "1.0F32 is float");
+_Static_assert(is_same<__decltype(0.5e0f32), float>::value, "0.5e0f32 is float");
+
+// 64-bit suffix -> double.
+_Static_assert(is_same<__decltype(1.0f64), double>::value, "1.0f64 is double");
+_Static_assert(is_same<__decltype(1.0F64), double>::value, "1.0F64 is double");
+_Static_assert(is_same<__decltype(0.5e0f64), double>::value, "0.5e0f64 is double");
+
+// Sanity check: the plain 'f' and 'h' suffixes still work.
+_Static_assert(is_same<__decltype(1.0f), float>::value, "1.0f is float");
+_Static_assert(is_same<__decltype(1.0h), half>::value, "1.0h is half");
+_Static_assert(is_same<__decltype(1.0l), double>::value, "1.0l is double");
+
+// The fixed-size suffix must not collide with an integer suffix.
+_Static_assert(is_same<__decltype(1.f32), float>::value, ".f32 with no fraction digits is float");