spirv-opt: Fix assertion with fp8

This patch fixes an assertion crash in Debug build.

However, hex_float.h contains some errors when converting float32 to
smaller floating point types, which causes incorrect results. Please see
KhronosGroup/glslang#4241 for details.

fixes: #6533

Author: GinShio

source/opt/folding_rules.cpp

@@ -153,7 +153,7 @@ std::vector<uint32_t> GetWordsFromScalarFloatConstant(
     const analysis::FloatConstant* c) {
   assert(c != nullptr);
   uint32_t width = c->type()->AsFloat()->width();
-  assert(width == 16 || width == 32 || width == 64);
+  assert(width == 8 || width == 16 || width == 32 || width == 64);
   if (width == 64) {
     utils::FloatProxy<double> result(c->GetDouble());
     return result.GetWords();

test/opt/fold_test.cpp

@@ -226,6 +226,7 @@ OpCapability Int16
 OpCapability Int64
 OpCapability CooperativeMatrixKHR
 OpExtension "SPV_KHR_cooperative_matrix"
+OpExtension "SPV_EXT_float8"
 %1 = OpExtInstImport "GLSL.std.450"
 OpMemoryModel Logical GLSL450
 OpEntryPoint Fragment %main "main"
@@ -238,6 +239,8 @@ OpName %main "main"
 %float = OpTypeFloat 32
 %double = OpTypeFloat 64
 %half = OpTypeFloat 16
+%float8e4m3 = OpTypeFloat 8 Float8E4M3EXT
+%float8e5m2 = OpTypeFloat 8 Float8E5M2EXT
 %101 = OpConstantTrue %bool ; Need a def with an numerical id to define id maps.
 %true = OpConstantTrue %bool
 %false = OpConstantFalse %bool
@@ -444,6 +447,10 @@ OpName %main "main"
 %half_null = OpConstantNull %half
 %half_0_1 = OpConstantComposite %v2half %108 %half_1
 %v4half_0_1_0_0 = OpConstantComposite %v4half %108 %half_1 %108 %108
+%float8e4m3_1 = OpConstant %float8e4m3 1.0
+%float8e4m3_0x1_4p_0 = OpConstant %float8e4m3 0x1.4p+0
+%float8e5m2_1 = OpConstant %float8e5m2 1.0
+%float8e5m2_0x1_4p_0 = OpConstant %float8e5m2 0x1.4p+0
 %106 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_0
 %v4float_0_0_0_0 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_0
 %v4float_0_0_0_1 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_1
@@ -1346,7 +1353,39 @@ INSTANTIATE_TEST_SUITE_P(TestCase, IntegerInstructionFoldingTest,
         "%2 = OpBitReverse %uint %111\n" +
         "OpReturn\n" +
         "OpFunctionEnd",
-    2, 0)
+    2, 0),
+    // Test case 98: Bit-cast float8e4m3 1 to float8e4m3
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%2 = OpBitcast %float8e4m3 %float8e4m3_1\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0x38),
+    // Test case 99: Bit-cast float8e4m3 1 to ubyte
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%2 = OpBitcast %ubyte %float8e4m3_0x1_4p_0\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0x3a), // FIXME: float8e4m3 1.4 is between 1.375 (0x3b) ~ 1.5 (0x3c)
+    // Test case 100: Bit-cast float8e5m2 1 to float8e5m2
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%2 = OpBitcast %float8e5m2 %float8e5m2_1\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0x3c),
+    // Test case 101: Bit-cast float8e5m2 1 to ubyte
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%2 = OpBitcast %ubyte %float8e5m2_0x1_4p_0\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0x3d) // FIXME: float8e5m2 1.4 is between 1.25 (0x3d) ~ 1.5 (0x3e)
 ));
 // clang-format on