[llvm] [SPIR-V] Implement SPV_KHR_float_controls2 (PR #146941)

[Marcos Maronas via llvm-commits]

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@@ -193,6 +196,20 @@ void buildOpSpirvDecorations(Register Reg, MachineIRBuilder &MIRBuilder,
     if (!DecorationId)
       report_fatal_error("Expect SPIR-V <Decoration> operand to be the first "
                          "element of the decoration");
+
+    // The goal of `spirv.Decorations` metadata is to provide a way to
+    // represent SPIR-V entities that do not map to LLVM in an obvious way.
+    // FP flags do have obvious matches between LLVM IR and SPIR-V.
+    // Additionally, we have no guarantee at this point that the flags passed
+    // through the decoration are not violated already in the optimizer passes.
+    // Therefore, we simply ignore FP flags, including NoContraction, and
+    // FPFastMathMode.
+    if (DecorationId->getZExtValue() ==
+            static_cast<uint32_t>(SPIRV::Decoration::NoContraction) ||
+        DecorationId->getZExtValue() ==
+            static_cast<uint32_t>(SPIRV::Decoration::FPFastMathMode)) {
+      continue; // Ignored.
+    }
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maarquitos14 wrote:

@MrSidims like we agreed, ignoring `spirv.Decorations` metadata related to FP flags --i.e. `NoContraction` and `FPFastMathMode`.

https://github.com/llvm/llvm-project/pull/146941