[llvm] [X86][ConstraintFP] Model rounding control registers for inline asm (PR #92846)

[Phoebe Wang via llvm-commits]

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@@ -1412,6 +1412,13 @@ EmitSpecialNode(SDNode *Node, bool IsClone, bool IsCloned,
       }
     }
 
+    // Add rounding control registers as implicit def for inline asm.
+    if (MF->getFunction().hasFnAttribute(Attribute::StrictFP)) {
+      ArrayRef<MCPhysReg> RCRegs = TLI->getRoundingControlRegisters(AsmStr);
+      for (MCPhysReg Reg : RCRegs)
+        MIB.addReg(Reg, RegState::ImplicitDefine);
+    }
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phoebewang wrote:

The use of rounding control requires parsing a lot of instructions or just unconditional add use here. I prefer to not do so in this patch.

https://github.com/llvm/llvm-project/pull/92846